PURDUE UNIVERSITY
GIRADUATE SCHOOL
Thesis Acceptance
c
Khis is to cenify that the thess prepared
ESy-.xateucme Diack
Eintitled
Residue Demn-psitioii of Cotton, Peanut and Sorgho
C:omplies with tJniversw regulat(ons and meets the standards of the G*aduare School for
and quality
For the degree of _ Ma.sterof!Science
-
--L
Signed by the final examining commIttee:
A p p r a v e d b -a;~&
y :

a
I
1
L-i
iS
This thesis
z is not to be regarded as
i-
Format Approved by:
-
- i-
Cha:r, Ftnaî Ewamtmng
Commirree
Thesas ir-na~ Adviser

---

RESIDUE DECOMPOSITION OF CO-l-l-ON, PEANUT
AND SORGHUM
A Thesis
Submitted to the Faculty
of
Purdue University
by
Mateugue Diack
in Partial Fulfillment of the
Requirements for the Degree
of
Master of Science
December 1994

---

ü
TO my family

---

. . .
111
ACKNOWLEDGMENTS
I express my gratitude and appreciation to Dr. D. E. Stott, my major
professor, for her guidance, ieadership, and research funds through the
Department of Agronomy throughout the course of my research.
I also wish to
extend my gratitude to the members of my advisory committee: Dr. Ron F. Turco,
and Dr. Eileen J. Kladivko for valuable discussion and information provided.
Thankfulness to the ARS-National Soi1 Erosion Lab, USDA, for the excellent
research facilities. Thanks to Glenn A. Wessies and all SCS agents for their
help in the collection of plant materials. Thanks to Barbara S. Condra for her
assistance in the lab.
Special th&ks are extended to my officemates Mark Risse, Thomas
Cochrane, Bayuo Liu, and Eusebio Ventura for their camaraderie.

---

iv
‘TABLE OF CONTENTS
P a g e
LIST OF TABLES ...................................................................................
vi
.l.. . . . .
. . .
LIST OF FIGURES.................................................................................
.<l.,
VIII
,..<.
ABSTRACT............................................................................................
./. .
xi
.
. . .
CHAPTER 1 LITERATURE REVIEW....................................................
.<i.<
1
,....
1.1. Faotors influencing Crop Residue Decomposition ............................. .,,..
2
,....
1 .l .l . Residue Charaoteristios ............................................................ .l.<
2
I....
1.1.1.1. Residue Type, Positioning and Placement ............................ .<I.<
2
,....
1.1.1.2. Residue Pankle Size.. ........................................................... .;.
4
. . . . .
1.1-l .3. Chemical Composition of Plant Residues .............................. .b.
4
,..,..
1.1.1.5. Biodegradation and Stabilization of Plant Residues in Soi1 H rnus
5
1.1.2. Soi1 Physical, Chemioal and Biologioal Properties.. ......................... . ..o.
9
l-1.2.1. Soil Type................................................................................
. ...*.
9
1.1.2.2. Soil Aoicky.. ...........................................................................
,,.....
9
1.1.2.3. Soit Fertility ............................................................................
,,....
1 0
1.1.2.4. Soil Miorobial Population, Tillage and Management Praotioe . . . . .
11
1.1.2.5. Soi1 Fauna ............................................................................. A.<,.....
1 2
1.1.3. Climatic Conditions .................................... ,,*. ................................... ,.,.. . . . . .
1 3
1.1.3.1. Soil Tempenature ................................................................... .k. . . . . .
1 3
1.1.3.2. Soil Moisture and Aeration...................................................... ..L. ,.....
1 3
1.1.3.3. Effects of Wetting and Drying, Freezing and Thawing.. ........ ,,...-.
1 4
1.2. Living Roots and Root Decomposition ..............................................
,,.....
1 5
1.3.. Referenoes .................................................... P.............;. ....................... . . . . . . . . 1 8
CHAPTER 2 SURFACE RESIDUE AND ROOT DECOMPOSITION
O F COlTON, PEANUT AND SORGHUM........................ . ...“..
31
.I.
2.1. Abstra ct.............................................................................................. , . . . . . . .
3 1
2.2. Introduction .......................................................................................
.“.....
32
2.3. Materials and Methods....................................................................... . . . ..a..
34
2.3.1. Soi1 ...........................................................................................
. . . . . . .
34
2.3.2. Plant Materiak.,.................................~........................................ . . . . . . . .
35
2.3.3. Chemioal Analyds of Plant Matenal ......................................... . ...<...
36

---

V
2.3.4. Plant Residue Mass loss Experiment ................................................
38
2.35. CO* Evolution.. ..................................................................................
40
2.3.6. Measurement of Specific Surface Area-W-Mass Ratio.. ....................
41
2.3.7. Statistical Analysis.. ...........................................................................
42
2.4. Results.. ......................................................................................................
42
2.4.1. Initial Chemical Composition.. ...........................................................
42
2.4.2. Initial Specific Surface Area ..............................................................
45
2.4.3. Initial Residue Mass.. ........................................................................
45
2.4.4. C lost as CO 2....................................................................................
46
2.4.5. Change i n Mass loss.. .......................................................................
66
2.5. Discussion.. .......; ........................................................................................
85
2.51. Change in the Specific Surface Area-to-Mass Relationship.. ............
90
2.5.2. Relationship between Mass loss and Carbon
loss.. ......................
102
2.5.3. Prediction of Residue Decay .........................................................
104
2.6. Conclusions.. ..........................................................................................
109
2.7. References..
111
.............. . ..............................................................................
CHAPTER 3 CROP RESIDUE DECOMPOSITION WITH CHANGE IN
SOIL DEPTH . . . . . . . . . . . . . . . . . . ..**....................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...*
114
3.1. Abstract.. .................................... . ...........................................................
114
3.2. Introduction.. ..........................................................................................
115
3.3. Materials and Methods ...........................................................................
116
3.3.1. Soi1 and Site Description ...............................................................
116
3.3.2. Plant Materials ..............................................................................
117
3.3.3. Decomposition Experiment.. .........................................................
,1 18
3.3.4. Incubation System........................................................................
119
3.3.5. Measurement of CO2 Evolution- ...................................................
119
3.3.6. Statistical Design ..........................................................................
120
3.4. Results and Discussion .........................................................................
120
3.5. Conclusion............................................................................................
126
3.6. References ...........................................................................................
127
U<e”s--mNl”-n---I-
._,
---
_ .

---

vi
LIST OF TABLES
Table
P a g e
2.1. Dates and locations iof the trop sample collection . . . . . . . . . . D
. . . . . . . . . . . . . . . . . . . i
3 5
2.2. Plant residue components and loading rates.,. . . . . . . . . ..- -._ . . . . . . . . . . . . . . 0. . . . ,
3 9
I
2.3. Initial chemical composition of the aboveground residues . . . . . . . . . . ...“....!
43
I
2.4. Initial chemical composition of the plant roots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...<.....
44
2.5. Relative initial mass and specifk surface area of the residue compo ”ents.46
2.61. Predictive ratio and rate constants of CO, loss and mass Ioss...........~~ 108
j
3.1” Initial chemical composition of the peanut residues . . ..o...................e..&e 117
3.2. Physical and chemical characteristics of the soil samples . . . . . . . . . . . . . . . . . . j..
121
Appendices
I
. . . . . . . . . . . . ..I..~....~....~~..........~~~.........-......*.......*...................--~....~~..~
/
129
Table
A. COz evolution from no-till and moldboard plowed soils amended !
with peanut residue. . . . . . . . . ..a....*............. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...“..+
130
B. CQz evolution from soil amended with cotton residue. ,.... - .- *...-. . . .L e 136
C. CO2 evolution from soil amended with peanut residue... . . . . . . . . . . . . . .-..i.*
139
0. COz evolution from soi1 amended with sorghum residue. . ..~~...~~.. *..:.-
142
E. Mass loss of wtt017 residue
,
. . ..~*...............~.................-....................~..
145
F. Mass loss of peanut residue . . . . . . ..“.........“..-.........................~...........~..
149
/
I
G. Mass loss of sorghum residue .~........._..^~...“.............~......................~..~ 153
H. Change in specifk: surface area of cotton residue ..,,........ a..e.0e . . . . -...iO..
157
1. Change in specific surface area of peanut residue..... . . . . . . 1 . . . . . a . . . . -..l.- 160
/

---

vii
J. Change in specific surface area of sorghum residue . . . . . . . . . . . . . . . . . . . . . . . . ..c.
1 6 3
K. Anova for CO2 bolution from no-tiil and plowed soils amended with
peanut residue . . .._.................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . .
1 6 6

---

/
I
. . .
I
vlu
LIST OF FIGURES
/
Figure
/
Page
,
2.1. Decomposition of cotton DL-P-5690 as measured by CO2 evoiution
’
over time. Bars represent standard deviations at given tirne... . . . . . . . . . . . . . . . . i
49
/
2.2. Decomposition of titton DP-5215 as measured by COz evolution
I
over time.
Bars repiesent standard deviations at given time . . . . . . . . . . . . . 0 ,.... ;.,,
50
2.3. Decomposition of cotton HS-46 as measured by CO2 evolution over timq...
51
2.4. Decomposition of cotton above-ground biomasss as measured by CO2 !
evolution over time . . . . . . . . . . . . . . . . . . . . . . . . . ..~.....-.......................~......~...~...............
i .II
52
2.5. Decomposition of cotton roots as measured by CO2 evolution over aime..;..
53
I
2.6. Decomposition of peanul: Florunner as measured by COz evolution
’
over time . .._..-.................... . . . . . . . . . . . . . f . . ._. . .. . . . . . . . . ..1....~*..~.......__..................... 5 4
2.7. Decomposition of peanut NC-7 as measured by COz evolution over tirne/.... 55
/
2.8. Decomposition of pez!nul: NC-1 1 as measured by COn evolution over tirnI,-.
56
2,9. Decomposition of pqanui: above-ground biomass as measured by CO2
’
evotution over time . . . . . . . . . . . . . . . . . . . . . . . . . .
i
..~.._.......~.................1......~............~......!...57
2.10. Decomposition of peanut roots as measured by CO* evolution over timh.,.
5 8
2.11. Decomposition of sorghum Triumph-266 as measured by CG evolutio i
over time . . . ..Y.............................................*....--..-.........“... . . . . . . . . . . . . . . . . . . <*
. . . . 1.s.
59
/
2.12. Decomposition of sorghum GW-744BR as measured by CO2 evolution /
over time . . . ..~.........................................-_.-...................-..........-..........~.... i.,..
60
2.13. Dlecomposition of sorghum Nking-300 as measured by Con evolution j
over time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
i
..-............*........_..................~.
61
/
2.14. Decomposition of sorghum above-ground biomass as measured by C$
evolution over time
/
. . . . . . . . . . . . . . . . . . . . . . . ..“~.....-~.~~....~.-.......“.....................~........~...
62

---

ix
2.15. Decomposition of sorghum roots as measured by COz evolution over time
6 3
2.16. Mean decomposition rate of the above-ground biomass for each of the three
crops as measured by COz evolution over time . . . . . . . . . . . . . . . .._........................
6 4
2.17. Mean decomposition rate of the roots for each of the three crops as
measured by COz evolution over time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6 5
2.18. Decomposition of cotton OLP-5690 as measured by mass loss over time.
6 8
2.19. Decomposition of cotton DP-5215 as measured by mass loss over time...
6 9
2.20. Decomposition of cotton HS-46 as measured by mass loss over time.......
7 0
2.21. Decomposition of cotton above-ground biomass as measured by
mass loss over time . . . . . . . ..*........................................................*.................
7 1
2.22. Decomposition of cotton roots as measured by mass loss over time.........
7 2
2.23. Decomposition of peanut Florunner as measured by mass loss over time
7 3
2.24. Decomposition of peanut NC-7 as measured by mass loss over time.......
7 4
2.25. Decomposition of peanut NC-1 1 as measured by mass loss over tirne......
7 5
2.26. Decomposition of peanut above-ground biomass as measured by
mass loss over . . . . . . . . ..~.._....................................................-.......*.................
7 6
2.27. Decomposition of peanut roots as measured by mass loss over tirne.......
7 7
2.28. Decomposition of sorghum Triumph-266 as measured by mass loss
over time . . . . . . . . . . . . .._....1*..._..................................*.............*....-.-...............-..~
7 8
2.29. Decomposition of sorghum GW744BR as measured by mass loss
over time . . . . . . . . ..-...............*............................... . . . . . . . . . . . . . . . . . ..-.......“*............a
7 9
2.30. Decomposition of sorghum Nking-300 as measured by mass loss
over time. . . . . . . . . . . . . . . ..s.....-......-..................
. . . . . . . . . . . . . . . . . ..*.......-......*..*.............
8 0
2.31. Decomposition of sorghum above-ground biomass as measured by
mass loss over time .__....__........................................................-.._........_.....
8 1
2.32. Decomposition of sorghum roots as measured by mass bss over tirne....
8 2
2.33. Mean decomposition rate of the above-ground biomass for each
of the three crops as measured by mass loss over time . .._........................
8 3

---

X
2.34. Mean decomposition.rate of the roots for each of the three crops
as measured by mass loss over time . . . . . ..~.. . ..~ ..,,. . . . . ~ . . . . . . . . . . . 9 . . . . . . . . . . .._. ~..
8 4
2.35. Change in specific surface area-to-mass for cotton DLP-5690 over tin
9 2
2.36. Change in specific surface area-to-mass for cotton DP-5215 over timr
9 3
2.37. Change in specific surl’ac.e area-tc-mass for cotton HS-46 over time...
9 4
2.38. Change in specific sut-face area-to-mass for peanut Florunner over tifl
9 5
2.39. Change in specific surface area-to-mass for peanut NC-7 over tirne....
9 6
2.40. Change in specifïc surface area-to-mass for peanut NC-1 1 over time..
9 7
2.41. Change in specific surface area-to-mass for sorghum Triumph-266
over time . . . ..*.......*.....f.....~.................................._..................................
9 8
2.42. Change in specifïc sucface area-to-mass for sorghum GW744BR
over time ..~.......................~..............~........-.........~..................................
99
2.43. Change in specific surface area-tc-mass for sorghum Nking300
over time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..~.........0.........~................*................. 100
2.44. C:hange in specific surface area-tc-mass for the three crops over time
101
2.45. Reiationship between mass loss and CO2 evolution for aboveground
biomass and roots of three cultivars of cotton, peanut and sorghum in
e eany
stage of decomposition ..-....................._...0......-...........-......................... . . . ...103
2.46. R.elationship between mass loss and predictive decay rate using
aboveground biomass and roots of three cultivars of cotton, peanut a1
sorghum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..~........“.........-....................~..............~...
..,,. 106
2.47. R:eiationship between CQ evolution and predictive decay rate using
aboveground biomass and roots of three cultivars of cotton, peanut a1
sorghum . . . . . . . . . . . . . . . . . . . ..<...................1..........D..~-........................~..........~...*
. . . . 107

---

xi
ABSTRACT
Diack, Mateugue. MS., Purdue University, December 1994. Residue
decomposition of cotton, peanut and sorghum. Major Professor: D.E. Stott.
Developing effective management strategies that protect soi1 against erosion
requires an understanding of residue decomposition. While the impact of
environmental factors such as temperature and water content has been studied,
little has been done to understand how the characteristics of the residue itself
impact the decomposition rate. Traditionally, the C:N ratio has been used as a
predictor of decomposition rates for agronomie crops, but has recently been
shown to be poorly correlated. This study relates the chemical composition of
residue components (aboveground biomass and roots) to the decomposition
rates for three cultivars each of three crops: cotton (Gossypium hirsufum),
sorghum (Sorghum bicolor) and peanut (Arachis hypogaea). The rates were
determined by mass loss and CO2 evolution. Change in the specific surface
area of the residue as related to mass loss was also measured. The three
crops were from slowest to the most rapid loss: sorghum > cotton > peanut.
From the initial chemical and physical residue characteristics, the following
equation was developed to predict decay in the first stage:
PO = (NSugars*Hemicellulose*&~.) / Lignin, where PD is the predictive decay
rate, &,. is the initial specific surface area-to-mass ratio.
For mass loss, ? =
0.96, and for CO* evolution, ?= 0.95. Since varietal differences within crops
have led to significant variation in decomposition rates, cultivars with slower
decaying residues might be recommended for highly erodible lands.

---

CHAPTER 1
LITERATURE REVIEW
Soil erosion is a major problem facing land managers, conservatio I
planners, environmental scientists and those concemed with construd 317 sites.
At the farming levei, erosion destroys the inherent fertility of the soil, a ld that
means higher farm and food costs.
Maintaining trop residue on the s il surface
is an effective and cost-effective practical method for controlling wind i nd water
erosion.
Douglas et al. (1992) noted that if residues are bumed, remc ied,
buried or decomposed before a critical erosion period, there may be ir ouffïcient
caver to protect the soil.
Critical time periods for wind erosion, when the potential for erosi( ir1 is the
greatest, occur from the ti#me of the last tillage before seeding until thj trop has
grown enough to provide adequate ground caver (Siddoway and Ferr$er, 1983).
This is when soil clods have dispersed due to freezing and thawing or; wetting
and drying, and when residue is usually positioned flat on the soit su I
rf!a ce.
Residue protects the .soPI surface from water erosion by absorbing the impact
energy of raindrops, thus reducing soi1 particle detachment. Residue, also
reduces surface crusting ,and sealing thereby enhancing infiltration a ,d
ri cxop
seediing emergence.
Surface residue slows the velocity of runoff waler by
creating small obstructions along the flow path. This action reduces bot,h the
amount of soil transported and the amount of additional soi1 particles libetached
by flowing water.

---

2
Managing trop residues on soit surface is a primary method for controlling
soil erosion. One of the main goals of conservation tiliage is to keep enough
trop residues on the soil surface to control or minimize erosion.
Generally, a
conservation tillage system that leaves 30°r6 of surface covered by residue, cari
reduce soi1 loss by 60-70%.
On steep slopes, greater caver is required to
achieve 604’0% soi1 loss reduction. Quantities of residue biomass left after
harvest depend on climatic conditions and soil nutrient availability during the
growing season. Surface residues in the standing position are twice as
effective in controlling wind erosion as the same quantity of residues lying flat on
the soi1 surface (Tanaka, 1986). However, flat residues are the most effective
for controlling erosion by water.
Understanding how rapidly surface managed trop residues are decomposed
and lost from a fïeld site, is a prerequisite to the design of erosion prediction and
control that Will ensure sustainable and profitable agriculture. The major factors
controlling trop residue decomposition are residue physical and chemical
characteristics, soi1 physical, chemical, and biological composition, and fïnally
climatic conditions (Stott et al., 1989).
1. i. Factors Influencing Crop Residue Decomposition
1.1.1. Residue C haraderistics
1.1.1.1. Residue Tvoe, Positioninq and Placement
Crop residue types are generally separated into two main entities which are
the above-ground biomass of the plant (sheath, stem and leaves), and the rocts.
The residue position within a field is important in determining the type of soi1
erosion that cari be best controlled. For protection from water erosion, flat
residues contribute more caver than standing, residues and this prote& the soil

---

surface from raindrop impact. However, standing residues persist londer
because of slower decomposition rates. For wind erosion, standing re idues
reduce the wind velocity near the soi1 surface (Steiner et al., 1993).
1
FI* 1: residue
caver increases surface roughness, acts as non-erodible material, and brevents
soi1 particle detachment. Tanaka (1986) studied the effect of chemica/and
stubble-mulch fallow on residue orientation and decomposition, and to ( empare
1
residue biomass of standing vvinter wheat residue on chemical fallow plbts to
that of spring wheat. From the chemical fallow plot, standing residue dith an
angle < 45’ from vertical, and flat residue with an angle > 45’ from verti a I were
collected separately. He found that quantities of chemical fallow
”
stand,ng
residue decreased, while flat residue increased at constant rates durin lihe
çi
summer fallow period. Tanaka hypothesized that the loss and gain of desidue
were due to repositioning of the standing residue.
,
Surface placement of U-OP residues cari be an effective practical m $t.hod for
erosion control. Microorganisms involved in the decomposition of trop/ residues
/
are sensitive to residue placement. Puig-Gimenez and Chase (1984) dhowed
that under identical incubation conditions in the laboratory, straw kepf ear the
surface of the soil and resiclue mixed uniformily through the 7 cm deep 1
:) oil
sample were not signifïcantly different in decomposition rate. In contrabt to
these results, fïeld studies have shown signifïcantly greater decomposit/on of
buried residues than of surface-applied residues (Greb et al., 1974). $ne
decrease in decomposition parallels, but likely not due to the drop in th 1 soi1
organic carbon level. Parr and Papendick (1978) stated that buried regidues
are likely to decompose fas,ter than surface residues because buried rekidues
are exposed to more uniforrn temperature and moisture conditions withib the soi1
profile.
Furthermore, in a study of wheat straw residue loss under simi lated
1
field conditions, Brown and Dickey (1970) observed that buried wheat r/xidue
/
had a greater mass loss thaln residue on the soil surface.

---

1 .1.1.2. Residue Particle Size
Few data are available on the effects of particle size on residue
decomposition.
In some faboratory decomposition studies, trop residues were
chopped into 4 to 5 cm sections, in others, ground residues were used. Large
particles generally decompose slower than small particulate materials (Allison,
1973). Jensen (1994) related decomposition rate with residue particle size and
C:N ratio, noting that the decomposition of plant residues was slower with small,
than with coarse residues in the early decomposition stage of materials of low
C:N ratio. He concluded that it was probably due to a better protection of the
smaller residues and biomass by cfay minerals. For residues with high C:N
ratio, the decomposition of larger sized residues may be N-limited, resulting in a
slower rate of decomposition compared to smaller residues.
Residue type, particle size, position and placement in the fïeld are all
important factors contributing to the regulation of the decomposition process.
1.1.1.3. Chemical Composition of Plant Residues
Chemical quality of the trop residues is one of the most important factors
controlling the rate of breakdown of the residues by microbes. Although
microbes do not have absolute control on nutrient availability, they are strong
competitors for available nutrients. The overall rate of decomposition is
infiuenced by the types of organic molecules and the nutrient content of the plant
residues (as well as by other factors being discussed). Nitrogen is a key
nutrient for microbial growth and hence for organic material breakdown.
Residue with high nitrogen contents favor rapid initial decomposition. Also, the
comportent most frequently limiting microbial adivity is the availability of
utilizable C substrate (Alexander, 1977).

---

5
In plants, about 75% of the dry weight is polysaccharide, with cellulbse, the
most abundant of all naturally occurring organic compounds, constituti g at least
4
10% of all vegetable matter (Cheshire, 1979). The cellulose has a st çtural
4
role; in the plant cell wall, liiiear chains of cellulose molecules occur in /Y,oss-link
1
bundles embedded in a higiMy branched polysaccharide matrix consistihg of
hemicellulose. Hemicelluloses have been defined as the alkali-solubla
polysat&arides in plant and are a mixture of homo- and heteropolysacparides
with xylans predominating. Plants also contain small amounts of wate I-soluble
i
polysaccharides.
I
Lignin is the second most abundant polymer synthesized by plantsi(Stott et
al., 1989). According to Lewis et al. (1990), lignins are plant polymerslderived
from the hydroxycinnamyl ailcohols or monolignols’ p-coumaryl, conife d1, and
sinapyl. They also noted that the aromatic portions of these phenylpr4panoids
are described as p-hydroxyphenyl (h), guaiacyl (g), and syringyl (s) mo,‘eties,
k
respectively, and that lignins are classified according to this distinction.!
Polysaccharide and lignin contents are important factors in the pIaIt residoe
decomposition.
Their initial concentrations play a major role in predic ing the
ti
kinetics of residue decomposition.
1 .l .1.5. E&dearadation ant~tabilization of Plant Residues in Soil Hu
Young succulént tissues are metabolized more readily than residugs of
mature plants. As the plant ages, its chemical composition changes; 1,he
content of nitrogen, proteins, an.d water-soluble substances fall, and te
proportion of cellulose, hernicallulose and lignin rises.
Soluble C cor$ounds
degrade fïrst, followed by structural polysaccharides (hemicellulose addl
cellulose), with lignin decomposing later at much slower rate (Wessen/and Berg,
1985; Summerell and Burgess, 1986; Reber and Schara, 1971).
Res/dues
having relatively high lignin contents, low N content or high C:N ratio degrade at

---

6
a slower rate (Ladd et ai., 1981; Pan and Papendick, 1978). However, more
recent work has shown that C:N ratio was closely related to the nature of the
plant residue (grain vs iegume), residue placement (Smith et al., 1986) and
residue particle size (Jensen, 1994). Lignin is a very complex, slowly degrading
compound, and high lignjn content retards decomposition.
Lignin is thought to be the major source of polyphenols. The role of lignin
as a regulator in the decomposition process has been elucidated in several
studies (Meentemeyer, 1978; Berendse et al., 1985). Increasing lignin
concentration reduces the decomposition rate of plant residues. High lignin
content of plant residues could also enhance nutrient immobilization, especially
of nitrogen (Melillo et al., 1982). Simple phenolic substances and other
aromatic co’mpounds may be present in plant and microbial residues, and are
released during biodegradation of aromatic polymers such as lignins (Flaig et
al., 1975; Kassim et al., 1982; Linhares and Martin, 1979).
Labeling of plant and mode1 lignins has greatly facilitated our knowledge of
the biodegradation and transformations of lignin during humification in soil (Kirk
et al., 1977). Within the soil humus, lignin biodegradation studies indicate that
lignin is an important substrate for humus formation (Stott et al., 1989).
The use of 14C-labeled substrates has made it possible to more precisely
follow the degradation and stabilization in humus of specific carbons (Stott et ai.,
1989). After one year, (Martin et al., 1980), in a 2-year biodegradation and
stabilization of specific trop, lignin, and polysaccharide carbons in soils study,
about 10 to 20% of the residual C Will be present in the soil biomass, and 80 to
90% of the residual C Will be in new humus (Stott et al., 1983a, b).
With time,
thle proportion of residual substrate carbon in biomass Will dedine and that in
humus Will increase (Kassim et al., 1982; Stott et al., 1989). In most soils, the
biomass constitutes about 2 to 4% of the organic carbon (Anderson and
Domsch, 1978; Jenkinson and Powlson, 1976). About 20% of the residual C
from readily biodegradable substrates Will be associated with the humic acid

---

7
fraction of soi1 humus, with some of it being present in aromatic molecuijes.
Martin et al. (1974a) found ‘t4C activity in over 16 phenolic compounds upon Na-
/
amalgam degradation of soil humic following incubation of soil amende+ with
14C-labeled glucose or wheat straw. Still, the greater part of the residual C is
present in peptides and polysaccharides and is released as sugar or amino acid
units upon acids hydrolysis (Jenkinson, 1971; Martin et al., 1980; OadeQ and
Wagner, 1971; Stott et al., ‘1963a; Wagner and Mutatkar, 1968). As Sktt et al.
(1983a) reported, this would be expected as the majority of metabolize/ C not
released as CO2 would be transformed into microbial protoplasm, cell wall
material, and polysaccharides. Sixty percent or more of most organic esidues
consist of cellulose and other polysaccharides. Some residues, such as
legumes and microbial tissue s, contain from 6 to as much as 65% protein (Stott
et al., 4989). Most of these materials are very biodegradable, but theyiwill
decompose at slower rates than simple sugars and amino acids, especially
during the early stages of decomposition. Still, after 6-12 months, Saderbeck
and Gonzalez (1977) reported that about 70 to 85% of the C Will evolve as CO2
/
in a field decomposition of ‘14C-labeled plant residues in the various SO~IS study.
About 6 to i6% of the residual C Will be present in1 soi1 biomass (Stott et al.,
1983a).
A vlast number of residue decomposition studies have found that Pl/ant
residue disappearance rates generally follow an exponential decay cu&e. The
absolute mass loss is relatively rapid in early stages, but slows with time. This
has been expressed by Stott et al., (1994) by the equation:
?????? ???????? ??????
(1.1)
/
where Mt is the residue mass per unit area remaining on the surface tl$day and
M, is the mass per unit are’a remaining on the ground the previous cla: ~1, R, is a

---

8
decomposition constant specific to a residue type and EF, measured as the
lower limit of moisture and temperature factors, is the environmental factor
determining the fraction of a decomposition day that has occurred during day t.,
This curve Will fit the decomposition pattern of most types of plant residues
within the same environment. The key variable is the Rop( value. In general,
the pattern of decomposition is explained by the chemistry of the organic
molecules present in the trop residues. Molecules that are readily degraded,
such as sugars, disappear quickly, whereas, recalcitrant Iignin and phenolic
molecules are degraded very slowly. Usually, a ranking order of decomposition
of the organics present in plant litter is as follows: sugars > hemicellulose >
cellulose > lignin > waxes > phenols. Varietal differences have been shown to
have an impact on decomposition rates of cereal and legume residues (Smith
and Peckenpaugh, 1986; Stott, 1992). These differences are likely to be due to
the proportions of these compounds.
Residue decomposition rate depends on the amount of residue as well as
the chemical and physical quality of the residue. Three pools of compounds are
generally identified as one readily decomposable pool including simple sugars,
starches, and other proteins, an intermediate pool with non structural
carbohydrates, and a more recalcitrant pool including Iignin and other structural
compounds.
These pools along with the environmental factors determine the
kinetics of residue decomposition.
Ghidey et al. (1985) established a residue decay equation based on change
in residue surface area with time. However, they made an assumption that trop
residue consists of solid stems of uniform length and diameter, and that
decomposition starts from the outside surface of the material and proceeds
linearîy inward. Based on what we know, microorganisms attack preferably the
most readily degradable part of a plant material first which is the inside part of
the stem in this case. In general, stems have more pronounced lignification on
the outside surface than in the interna1 part. Stott et al. (1992) have found that

---

9
corn and soybean stem surface areas changed insignificantly over timc ; while
leaf area changes were very significant, Steiner et aL(1993) mentions rl that
decomposition may occur in the stem’s interior, leaving the stem exteril )r (and
caver) relatively intact.
1.12. Soil Physical, Chemical and Biological Properties
1 .1.2.1 D
Soil Type
It has been shown that the presence of clay Will increase microbial numbers
and activity in soil and pure cultures, especially during the early stage3 of
degradation of readi’ly available organic substrates (Filip, 1975). Grec orich et
al. (?~$II) also reported that the rate of decomposition of substrate C LJI 3s
greater in soils with more clay, in a study of the influence of soil texture on the
turnover of C through the microbial biomass, For organisms, associat en with
clay may offer a favorable ecological niche because the clay surface t-r ay have
concentrated substrate for the organisms. Bacteria adhere to both ch; Irged and
noncharged surfaces, and it l-nas been suggested that surface charges 3re not
importa.nt (C)rades et al., 1989). However, the interaction of clay partic es and
cells is dependent on the size and the charge of exchangeable cations and on
electrolyte concentration, just as for other negatively charged colloidal 2articles.
The interaction of microorganisms with clays is an area of expanding ir terest ,
as clays may prevent the potential spread of a disease-causing organir ;m-e.g.,
Fusarium-or may protect bacteria and viruses against extremes in the ’
environment and against sferilants (Strozky, 1980). Clays may also idcrease O2
uptake by microbial cultures (Filip et al., 1972; Haider et al., 1970; Strdzky,
1967).
The presence of clay, however, may reduce total C loss as CC/2 through
increasing the efficiency of C conversion to biomass and through formibg
complexes with decomposition products and new humus colloids (Gre/ves and
Wilson, 1973; Greenland, ‘1971; Martin et al., 1976). In a 1 O-year stu#y by

---

1 0
Jenkinson (1977) soils with higher clay contents retained greater amounts of the
C of added 1%labeled residues. Guekert et al. (1977) observed that intimate
association of glucose, microbial polysaccharide, and bacterial cells with clay
reduced the evolution of C as CO2 during incubation in soil.
Soil texture and soil organic matter have a great effect on residue
decomposition.
Microbial population and activity are expected to be high with a
soil high in organic matter and clay content.
1.1.2.2. Soil Aciditv
Hydrogen ion concentration is another factor influencing carbon turnover
Irates.
Each microbial species has an optimum pH for growth and a range
outside of which no cell proliferation takes place. Loss of C from organic
substrates may be slower in acid soils especially during the early stages of
decomposition (Jenkinson, 1971). Consequently, the treatment of acid soils
Mith lime accelerates the decay of plant tissues, simple carbonaceous
zompounds, or native soil organic matter (Afexander, 1977).
Measurements of pH are important criteria for predicting the capability of
soils to support microbiat activity.
1.7.2.3. Soil Fertility
Crop residues play an important role in maintaining soil fertility and
3roductivity by providing a source of nutrients and inputs to organic matter.
Soil
Drganic matter is the major source of N, S, P, and many micronutrients in soils.
Drganic matter is critical to efficient trop production because of its cation
2xchange and water holding capacities.
Crop residues , including roots, are the
3rimar-y source of organic material added to soil in many cropping systems.
rhey represent a major contribution to nutrient cycling. C and N availability

---

11
within trop residues along wifh lignin content greatly influence decomposition
rates and N availability to plants. Decomposition of residues with low N
contents such as wheat and grain sorghum may result in microbial
immobilization of soil and fet-tilizer N, and effectively reducing N availability to
plants (Reinertsen et aI.il 9’84; Vigil et al., 1991).
1.1.2.4. Soi1 Microbial Population, Tillaoe and Manaoement Practices
Soil microbial population in relation with management practices inflbences
trop residue decomposition in the field.
/
In a 2-year decomposition study conducted on corn, wheat, and soybean
residue, Brader (1988) found that bacterial and actinomycete populations were
consistently higher on soybean residue in comparison with corn and wheat
residue.
However, fungal populations were consistently highest on Co(n residue
and lowest on wheat residue. Stott et al. (1989) reported that in arid zone soils,
which are predominantly alltaline, the bacteria and streptomycetes would be
more active in organic resiclue decomposition. The fungi however, bave a much
greater biomass (Anderson and Domsch 1973); they are able to grow at Iower
moisture contents, and are no doubt important contribution to residue
biodegradation in desert sails.
Soil microbial populations have been fq hund to
differ between conventional tillage and no-till syst,ems.
Plowing and CI Itivation
accelerate the microbial processes involved in oxidizing organic matter
Doran
(1980) reported that nortiII had more total biomass than did convention 11 tillage
soils in the surface O-7.5 cm, which was related to an increase in soil LI ater
content, percent organic carbon, and nitrogen levels. Doran (1980) al ;o found
.
that. these results were reversed at the 7.5-l 5 cm ldepth. He concludes f that this
was probably due to the placement of trop residue at depth with plowir g, which
raised the soil water and organic carbon content.

---

1 2
Changes in soil organic t-natter reactions, as determined by organic car-bon
content, have strong implications on the microbial activity. The distribution of
organic carbon (OC) in the soi1 profile is a direct reflection of the management
practices in a given soil. The percent of OC tends to be greater in the no-till
surface O-7.5 cm than under conventional tillage, although the two systems show
similar organic carbon content through the remainder of the soil profile (Dick,
1984; Doran, 1980). The buildup of OC at the surface from no-till management
reflects the localized distribution of plants residues on the surface.
1 .1.2.5. Soil Fauna
Soi1 meso and macro animals are also involved in organic debris
degradation in many ecosystems, and interest in their activities is increasing.
Soil fauna are known to play a critical role in the biological turnover and nutrient
release of plant residues by fragmenting the plant residues, resulting in
enhanced microbial activities and grazing of microflora by fauna . Edwards and
Heath (1963) reported that when soil animals are excluded from decomposing
litter, via small mesh litterbag, fragmentation is insufficient and this leads to
reduce consumption by microorganisms. Schaller (1968), pointed out that
earthworms and soil insects are ver-y active in the disintegration of organic litter
accumulated on soil surfaces. Earthworm activity, greater in no-till systems, has
been implicated in increased rates of corn residue breakdown (Zachman et al.,
1989). Termite feeding activities were observed in litter decomposition and they
accounted for much of the mass loss in a litter decomposition study (Cepada et
al., 1990).
Soil macrofaunal activity cari have an important effect on residue
decomposition in an ecosystem appropriate for their living conditions. Not only
do they break down the relatively large particles of residue and trigger the

---

13
decomposition process, but also feed themselves on the residues, redt&ing
considerably the amount of residues present.
1.1.3. Climatic Conditions
1.1.3.1. soil Temoerature
Temperature is a major environmental factor for controlling residuej
decomposition rates in soil. Qrganic residue decomposition rates increase as
temperature increases (Stott et al., 1989). Although each species of t$e soi1
population has a temperature optimum, the overall optimum range in slils is
generally about 20 to 27’C in temperate climatic zones. Below this rabge, the
decomposition rate Will decrease and Will essentially be stopped when ’
surrounding environs freeze (Stott et al., 1989). In a study on wheat ’
decomposition, Stott et al. (1986) established equations for the relatiodship
between the amount of residue decomposition and temperature. Thed observed
that there was still significant amount of residue decomposition at O°C,iwith 12 to
17% [l’4C]COz evolved as CO2 in 30 days. The decomposition decredsed with
the temperature.
1.1.3.2. Soi! Moisture and Aeration
-
-
Soi1 moisture status is another important environmental factor regjlating
residue decomposition (Kclwalenko et al., 1978). Favorable moisture /conditions
for org’anic residue decomposition in soils range from about 50 to 90%/ of the
moisture-holding capacity (-50 to -15 kPa) as reported by ( Stott et al. \\ 989).
As the moisture content decreases below 50% of capacity, the activity iof the soil
organisms decreases, but some biodegradation occurs even at about $%
moisture (-1.5 MPa ), which is the permanent wilting point for most pl ints (Focht

---

and Martin, 1979). In a laboratory study on wheat residue decomposition, Stott
et al. (1986) found that significant decomposition still occurred at -5 MPa, with
10% of the residue C evolving as CO2 over one month.
Brown (1976), and
Griffin (1972) reported that many soil organisms Will live and even thrive at water
potentials much lower than -1.5 MPa.
Wilson and Griffin (1983) estimated that
6 out of II basidiomycetes tested grew at water potentials below -10 MPa.
A decreased rate of decomposition of 14C-labeled plant residues in planted
soi1 compared with fallow soi1 has been attributed to lower microbial activity
resulting from restricted aeration (Füer and Sauerbeck, 1968). Linn and Doran
(1984) found that aerobic microbial respiration increased with soil water content
and reached a maximum at 60% water filled pore space. Above 60% water
filled pore space, air became limiting. In well-drained soils, acids and alcohols
are formed, but they rarely accumulate in appreciable amounts because they are
readily metabolized by aerobic bacteria, actinomycetes, and fungi. The main
products of aerobic carbon mineralization are CO*, water, microbial cells, and
soil humus components. In the absence of 02, organic carbon is incompletely
metabolized, intermediary substances accumulate, abundant quantities of CH4
and smaller amounts of H2 are evoived.
~ 1 .1.3.3. Effects of Wettina and Drvinq, Freezinq and Thawinq
Under the low humidity and high temperatures frequently encountered in
arid zones, soils are subject to rapid drying following rains and irrigation (Stott et
al., 1989). They also reported,that in areas where the winter temperatures drop
below freezing, soils are subject to freezing and thawing cycles. Shields et al.
(1974) noted that the drying and rewetting or the freezing and thawing of soils
cause a marked flush in CO2 evolution. A decrease in bacterial numbers upon
drying and an increase in soluble amino acids and bacterial numbers following
rewetting have been observed by Stevenson (1956). Shields et al. (1974) found

---

1 5
that freezing and thawing were more effective than wetting and drying cycles in
musing the release of previously stabilized 14C as CO2 from the soils. ‘The
l
wetting and drying increased the evolution of previously stabilized 14C from 16
to 121% compared to controls kept continuously moist (Stott et al., 1989).
Salonius (1983) pointed out that a major factor in the increase CO2 evol/ution
was related to death of vegetative microbial cells during the freezing or drying
process.
After conditions blecome favorable for growth, the surviving otiganisms
quickly decompose the killed cells (Shields et al., 1974).
1.2. Living Roots and Root Decomposition
The value of roots as a source of organic matter is ably demonstrated by the
high organic matter content of grassland soils (Cook, 1962). Among the
extremely diverse soil microsites, which govern the activity and survivali of
microorganisms, the soil-root iinterface plays an important role, particularly in
modifying the density, activity and structure of the microbial communities. Plant
roots continuously provide the soil with small amounts of a wide varietyjof easily
decomposable materials, tt-lereby creating a rhizosphere effect (Curl and
Truelove, 1986). The rhizosphere is a microhabitat for microorganisms, most of
thern dependent on soluble exudatesfrom the root (Dormaar, 1990). The
microbial and chemical composition of the rhizosphere differs consider$bly from
that in the soil not influenced Iby roots (Curl and Truelove, 1986). Billeb and
Bot‘tner (1981) and Bottner (1982) observed that wheat root litter seemed to
disappear faster when. living roots were present. The release of all organic
material, both soluble and insoluble from roots, occurs during plant grohh
(Newman, a!385). Cheng ancl Coleman (1990) reported that living roojs had a
stimulatory effect on soil organic matter decomposition due to higher microbial
activity induced by the roots.

---

16
There have been few studies of decomposition of roots in any ecosystem
(Berget ai., 1984), and there are numerous difficulties in following the
decomposition of roots in the soil under natural conditions (Jenkinson, 1965).
However, as Berg et al. (1984) pointed out, not only is quantification of root
( decomposition necessary, but also it is important to understanding the factors
regulating the decomposition process. In a study of in situ decomposition of
root-derived carbon from wheat, Martin (1989) observed that the decomposition
of root-derived organic material, present in the wheat rhizosphere, was more
complete in undisturbed soil than when air-dried roots were mixed with moist or
~
air-dry soil. His explanation was based on the assumption that the airdrying
and mecha’nical disturbance killed a large part of the rhizosphere biota present
around roots in undisturbed soils. Berg et al. (1987) found that organic matter
mass loss, from red clover root decomposition, was fast during the first 13 days
(44%) and almost ceased after 30 days when about 29% of the organic material
remained.
They also noticed that there was no notable difference in mass or
nitrogen loss from roots of different diameters. The C:N ratio of the root
remains decreased from initially 2527 to 11:13 at the end of the incubation.
Root decomposition occurs continuously and peaks in early summer, then
~ declines to low levels during winter, and is in phase with soil temperature
(Santantonio et al., 1987). Joslin et al. (1987) also reported that root
decomposition rate (% weight loss) was highest during the August-September
~ inter-val, showing a positive correlation with soi1 temperature when studying the
association of organic matter and nutrients with fine root turnover in a white oak
stand.
Rates of mass losses of roots in a desert soil were equal to or higher
than those reported from mesic ecosystems by Whitford et al. (1988).
The hypotheses to test were that there is difference in decomposition rate
b’etween cultivars of a given plant species based on their initial chemical and
physical composition, and that these characteristics cari be used to predict
decomposition rate.

---

17
The objectives of this study were to: (i) determine decomposition rades for
cotton, peanut and sorghum aboveground residues and roots by carbon loss and
mass loss; (iii) determine the impact of initial chemical and physical
characteristics of the residues on decomposition; (iii) determine if plant ppecies
affects decomposition rate observed; (iv) determine changes in the mas/s-to-
specific surface area duringi decomposition, and (v) develop predictive <becay
equations for plant residues based on mass loss or CO2 loss and the chemical
and physical characteristics off the residues.

---

1 8
1.4. References
Alexander, M. 1977. Introduction to Soi1 Microbiology. Second ed. Wiley & Sons
Inc., New York City, NY.
Allison, F.E. 1973. Soil organic matter and its role in trop production.
Elsevier, Amsterdam, The Netherlands.
Anderson, J.P.E., and K.H. Domsch. ‘l973. Quantification of bacterial and fungal
contributions to soi1 respiration. Archives Microbiol. 93:113-127.
Anderson, J.P.E., and K.H. Domsch. 1978. Mineralization of bacteria and fungi
in chloroform-fumigated soils. Soil Biol. Biochem. 10:207-213.
Berendse, F., B. Berg, and E. Bosatta. 1985. The effect of lignin and nitrogen on
the decomposition of litter in nutrient-poor ecosystem: A theoretical
approach. Canadian J. Bot. 65: Il 16-l 120.
Berg, B., and 0. Theander 1984. Dynamics of some nitrogen fractions in
decomposing scot pine needle litter. Pedolobiol. 27:261-267.
Berg, B., M. Muller, and B. Wessen. 1987. Decomposition of red clover
(Trifolium Prafense) Roots. Soil Biol. Biochem. 19589593.
Billes, G., and P. Bottner. 1981. Effect des racines vivantes sur la décomposition
d’ une litière racinaire marquée au 1%. Plant Soil 62:193-208.
Bottner, P. 1982. Biodégradation du matériel végétal en milieu herbacé. Acta
OecoVOecol Generalis 3: 155-l 82.
Broadbent, F.E., and A.G. Norman. 1946. Some factors affecting the availability
of organic nitrogen in soil. A preliminary report. Soil Sci. Soc. Am. Proc.
Il :264-267.

---

19
Broder, M.W., and G.H. Wagner. 1988. Microbial colonization and
decomposition of corn, <wheat, and soybean residues. Soi1 Sci. Soc.!Am. J.
52:112-l 17.
Brown, .A.D., 1976. Microbial water stress. Bacteriol. Reviews 40:803-896.
Brown, P.L., and D.D. Dickey. 1970. Losses of wheat straw residue under
simulated field conditions. Soil Sci. Soc. Am. Pr-oc. 34:118-121.
Cepeda,, G.J., and W.G. Whitford. 7990. Decomposition patterns of sudace leaf
litter of six plant species along with a Chihuahuan desert watershed. The
Amer. Midland Naturalist 123:319-330.
Chen, M., and M. Alexander. ‘1973. Survival of soit bacteria during prolonged
desiccatjon. Soil Biol. Biochem. 5:213-221.
Cheng, W., and D.C. Coleman. 1990. Effect of living roots on soil orgad ic matter
decomposition. Soil Biol. Biochem. 22:781-78:7.
Cheshire, M.V. 1979. Nature, and origin of carbohydrates in soils. Unite& States
Edition. Academic Press Inc., New York City, NY.
Cook, F!.L. 1962. Soil management for conservation and production. Wbley and
Sons Inc. New York City, NY.
Crawford, R.L. 1981. Lignin biiodegradation and tr’ansformation. Wiley
Interscience Press. New York City, NY.
Curl, E.A., and B. Truelove. 1’986. The rhizosphere. Springer, New York City,
NY.
Dagley, S. 1971. Catabolism of aromatic compounds by microorganisms.
Adv. Microb. Physiol. 6: l-46.

---

20
Dick, W.A. 1984. influence of long-term Mage and trop rotation combinations on
soil enzyme activities. Soil Sci. Soc. Am. J. 48569-584.
Doran, J.W. 1980. Soil microbial and biochemical changes associated with
reduced tillage. Soil Sci. Soc. Am. J. 44:765-771.
~
Dormaar, J.F. i990. Effect of active roots on the decomposition of soil organic
materials. Biol. Fertil. Soils. l O:lZl -3 26.
Douglas Jr., C.L., P.E. R&smussen, and R.R. Allmaras. 1992. Nutrient
distribution following wheat-residue dispersa1 by combines. Soil Sci. Soc.
Am. J. 56: 1171 -i 177:
Edwards, C.A., and G.W. Heath. 1963. The role of soil animals in breakdown of
leaf material. In J. Doeksen & J. van der Drift [ed.], Soi1 organisms, North-
Holland Publ. CO., Amsterdam, The Netherlands.
Edwards, C.A., and J.R. Lofty. 1972. Biology of earthworms. Chapman and
Hall, London, England..
Elliott, L.F., H.F. Stroo. R.I. Papendick, C.L. Douglas, G.S. Campbell, and D.E.
Stott. 1986. Decomposition of surface managed trop residues. pp. 81-91.
In: L. F. Elliott [ed.] STEEP Conservation concepts and accomplishments.
Washington State University Press. Pullman, WA.
Filip, Z., K. Haider, and J.P. Martin 1972. Influence of clay minerals on formation
of humic substances by Epicom nigram and Stachybotrys chartarum. Soil
Biol. Biochem. 4:147-l 54.
Filip, Z. 1975. Wechselbezichungen zwischen mikroorganismen and
tonmineralen und ihre auswirkung auf die bodendynamik. In: D. E. Stott.
1989. Organic matter decomposition and retention in arid soils. Arid Soil
Research and Rehabilitation. 3:115-l 48.

---

-- -.-.-.--- “--“.. -. I-.< .“,” -..-l.,-l,.-<-.--l 1_ .--, ,__-
,a. .._” --“_ -___-_
2 1
Flaig, W., H. Bentelspacher, and E. Rietz. 1975. Chemical compositioni and
physical properties of humic substances. pp. I-21 1, In: J.E.Giesd&g, [ed.],
Soil components, vol. 1. Organic Components. Springer-Ver-kg, N$w York,
NY.
Focht, D.D., and J.P. Martin 1979. Microbiological and biochemical aspects of
semi-arid and agricultural soils, pp. 119-147. In: A. E. Hall, G.H. C ‘nnell,
and H.W. Lawton, [ed.], Agriculture in Semi-alrid Environment. Spri“R ger-
Verlag, New York, NY.
Führ, W., and D. Sauerbeck. 1968. Decomposition of wheat straw in the fïeld as
influenced by cropping and rotation. pp. 241-250. In: Isotopes and radiation
in soil organic matter studies. International At.omic Agency, Vienna,: Austria.
Ghidey, F., J.M. Gregory, T.R. McCarty, and E.E. Alberts 1985. Residub decay
evaluation and prediction.. Trans. of the ASAE,. :OOOl -2351 :102-l 04.
Goering, H.K., and P.J. Van Soest. 1970. Forage fiber analysis. Agricutture
Handbook No. 379. Aglzicultural Research Service. USDA. Jacket No. 378-
598.
Greaves, M. P., and M.J. Wilson. 1973. Effect of soil microorganisms on
montmorillonite- adenine complexes. Soil Biol. Biochem. 5:275-276.
Greb, B.W., A.L. Black, and D.E. Smika. 1974. Straw buildup in soil with stubble
mulch fallow in the semi-arid Great Plains. Soil Sci. Am. Proc. 38: 135-l 36.
Greenland, 0. J. 1971. Interactions between humic and fulvic acids andi clays.
Soil Sci. 111:34-41.
Gregorich, E.G., R.P. Voroney, and R.G. Kachanaski. 1991. Turnover bf carbon
through the microbial biornass in soils with different textures. Soil I iol.
Biochem. 23:799-805.

---

22
Gregory, J.M., T.R. McCarty, F. Ghidey, and E.E. Alberts. 1982. Derivation and
evaluation of a residue decay equation. Trans. of the ASAE. OOOI-2351:98,
99, 101, 105.
Griffin, D. M. 1972. Ecology of soil fungi. Syracuse University Press, Syracuse,
New York.
Griffith, D.R, E.J. Klavdivko, J.V. Mannering, T.D. West, and S.D. Parsons.
1988. Long-term tillage and rotation effects on corn growth and yield on high
and low organic, poorly drained soils. Agron. J. 80599605.
Guekert, A., H.H. Tok, and F. Jacquin. 3977. Biodégradation de polysaccharides
bactérieux adsorbés sur une montmorillonite. pp. 403-411, In: Proc. of the
inter. symp. on soi1 organic matter studies. Vol. 1. international Atomic
Energy Agency, Vienna, Austria.
Hackett, W.F., W.J. Conners, T.K. Kirk, and J.G. Zeikus. 1977. Microbial
decomposition of synthetic A%-labeled ligninsin nature: lignin
biodegradation in a variety of natural materials. Environ. Microbiol.
33:43-51.
Haider, K., 2. Filip, and J.P. Martin. 1970. Einfluss von montmorillonite auf die
bildung von biomasse und stoffwechsel- zwischenproducten durch einige
mikroorganismen. Archives Mikrobiologie. 73:201-215.
Haider, K., and J.P. Martin. 1975. Decomposition of specifically carbon-14-
labeled benzoic and cinnanic acid derivatives in soil. Soi1 Sci. Am. Proc.
39:651-662.
Haider, K., J.P. Martin, and Z. Filip. 1975. Humus biochemistry, pp. 195-244, in:
E. A. Paul and A.D. Mclaren fed.] Soi1 Biochemistry. Vol. 4. Marcel Dekker,
New York City, NY.
Haider, K., J.P. Martin, and E. Rietz. 1977. Decomposition in soi1 of A%-labeled
coumaryl alcohols, free and linked into dehydropolymer and plant lignins
and mode1 humic acids. Soi1 Sci. Soc. Am. J. 411556-562.

---

23
Haider, K., and J.P. Martin. 1979. Abbau and umwand lung von
ruckstanden und ihren Inhaltsstoffen durch die mikroflora des bod
Zeitschrift fur Pflanzenernahrung under Bodenkunder
Hargrove, v\\/.L., P.B. Ford, and Z.C. Somda. 1992. Crop residue decomposition
under controlled and fieldl conditions. Station Bulletin. Dept. of Agronomy,
Uniiv. of Georgia, Georgia Station, GA 30223-I 797.
Herman, W.,A., W.B. McGill, and J.F. Dormaar. 1977. Effects of initial c&emical
composition on decomposition of roots of three grass species. Car$ J. Soil
Sci. 57205215.
Jenkinson, D.S. 1965. Studies on the decomposition of plant materia! i
Losses of carbon from 14C labeled ryegrass incubated with soi1 in
J. Soil Sci. 16:104-l 15.
Jenkinson, D.S. 1971. Studies on the decomposition of 1%labeled organic
matter in soil. Soil Sci. 111:64-70.
Jenkinson, D.S. and D.S. Powlson. 1976. The effects of biocidal treatments on
metabolism in soil. V. A method for measuring soi1 biomass. Soil Bibi.
Biochem. 8:209-213.
Jenkinson, D.S. 1977. Studies on the decomposition of plant material in soil. V.
The effects of plant caver and soi1 type on the loss of carbon from 14C-
labeled ryegrass decomposing under field conditions. J. of Soil Scii
28: 417423.
Jenkinson, D.S., and A. Ayanaba. 1977. Decomposition of carbon-14-labeled
plant material under tropical conditions. Soil Sci. Soc Am. J. 41:91!2-915.
Jensen, E.S. 1994. Mineralization-immobilization of nitrogen in soi1 ambnded
with low C:N ratio plant residues with different particle sizes. Soil Biol.
Biochem. 26:519-521.

---

24
Joslin, J.D., and G.S. Henderson. 1987. Organic matter and nutrients
associated with fine root turnover, in a white oak stand. Forest. Sci.
33:330-346.
Kassim, G., J.P. Martin, and K. Haider. 1981. Incorporation of a wide variety of
organic substrate carbons into soil biomass as estimated by the fumigation
procedure. Soi1 Sci. Soc. Am. J. 45:1106-l 112.
Kassim, G., D.E. Stott, J:P. Martin, and K. Haider. 1982. Stabiiization and
incorporation into biomass of phenolic and benzenoid carbons during
biodegradation in soil. Soil Sci. Soc. Amer. J. 46:305-309.
Kirk, T.K., W.J. Connors, and J.G. Zeikus. 1977. Advances in understanding the
microbiological degradation of lignin. Adv. in Phytopathol. 11:369-394.
~
Knapp, E.B., L.F. Elliott, and G.S. Campbell. 1983. Microbial respiration and
growth during the decomposition of wheat straw. Soil Biol. Biochem. 15:319-
323.
~
Kowalenko, C.G., K.C. Ivarson, and D.R. Cameron. 1978. Effect of moisture
content, temperature, and nitrogen fertilization on carbon dioxide evolution
from field soils. Soil Biol. Biochem. 10:417-423.
Ladd, J. N., J. M. Oades, and M. Amato. 1981. Microbial biomass formed from
‘4c , ‘5N-l,abeled plant material decomposing in soils in the field. Soil Biol.
Biochem. 13: 119-I 26.
Leisola, M.S.A., and A. Fiechter. 1985. New trends in lignin biodegradation. Adv.
Biotechnol. Process. 559-89.
: Lewis, N.G., L. Davin, T. Umezawa, E. Yamamoto. 1990. On the biosynthesis of
(+) pinoresinol in Forsythia suspensa. Annu. Rev. Plant Physiol. Plant Mol.
Biol. 41:455-496.

---

25
Linn, D.M., and J.W. Dot-an. 1984. Aerobic and anaeobic microbial populations
in no-till and plowed sois. Soil Sci. Soc. Am. J. 48:794-799.
Linhares, L.F., and J.P. Martin. 1978. Decomposition in soil of humic aci/d-type
polymers (melanins) of I%otium echinulafum, Aspergihs glaucus s@., and
other funlgi. Soil Sci. Soc. Am. J. 42:738-743.
Linhares, L.F., and J.P. Martin. 1979. Decomposition in soil of emodin,
chrysophanic acid, and a rnixture of anthraquinones synthesized by’an
,clspergi/hs glaucus isolate. Soil Sci. Soc. Am.. J. 43:940-945.
Martin, J. P., K. Haider, and Saiz-Jiminez. 1974a. Sodium amalgam reductive
degradation of fungal-and mode1 phenolic polymers, soil humic acida, and
simple phenolic compounds. Soil Sci. Soc. Am. Proc. 38:760-765.
Martin, J.P., I<. Haider, W.J. Fat-mer, and E. Fustec-Mathon. 1974b.
ecomposition and distribution of residual actlvities of some l%-microbial
polysaccharides and cells, glucose, cellulose ;and wheat straw. Soil IBiol.
Biochem. 6:221-230.
Martin, J.P., and K. Haider. 1976. Decomposition of specifically car-bon-“l,4-
Iabeled ferulic acid; free and linked into mode1 humic acid-type polymers.
Soil Sci. Soc. Am. J. 40:377-380.
Martin, J-P., and D.D. Focht. 1977. Biological properties of soils, pp. l l$-172,
In: L..F. Elliott and F.J. Stevenson [ed.], Soils far management of organic
wastes, and waste waters. Amer. Soc. Agron., Madison, WI.
Martin, F.C., Saiz-Jimenez, and A. Cet-t. 1977. Pyrolysis-gas chromatography of
soi1 humic fractions. 1. The low boiling point compounds. Soil Sci. Soc. Am.
J. 44:1114-1118.
Martin, J.P., A.A. Parsa, and K. Haider. 1978. Influence of intimate association
with humic polymers on biodegradation of [14C,] labeled organic substrates in
soil. Soil Biol. Biochem. lQ483-486.

---

26
Martin, J.P., and K. Haider, and G. Kassim. 1980. Biodegradation and
Stabilization after 2 years of specific trop, lignin , and polysaccharide
carbons in soils. Soi1 Sci. Soc. Am. J. 44:1250-1255.
Martin, J. K. 1989. In situ decomposition of root-derived carbon. Soil Biol.
Biochem. 21:973-974.
~
McClaugherty, C.A., J. Pastor, J.D. Aber, and J.M. Melillo. 1985. Forest litter
decomposition in relation to soil nitrogen dynamics and litter quality. Ecology
66:266-275.
Meentemeyer, V. 1978. Macroclimate and lignin control of litter decomposition
rates. Ecology 59:465-472.
~
Melillo, J.M., J.D. Aber, and J.F. Muratore. 1982. Nitrogen and Iignin control of
hardwood leaf litter decomposition dynamics. Ecology 63:621-626.
~
Myrold, D.D., L.F. Elliott, R.I. Papendick, and G.S. Campbell. 1981. Water
potential-water content characteristics of wheat straw. Soil Sci. Soc. Am. J.
45:329-333.
~
Newman, E.I. 1985. The rhizosphere: car-bon sources and microbial populations.
In: A. H. Fitter [ed.] Ecological interactions in soi1 pp. 107-127. Spec.
publ. series of the British Ecological Society 4, Oxford, England.
Oades, J.M. 1989. An introduction to organic matter in minera1 soils. in:
J. 9. Dixon and S. B. Weed [ed.] Minerals in soil environments. Second
edition. Soil Sci. Soc. Am. pp. 89-159.
Oades, J.M., and G.H. Wagner. 1971. Biosynthesis of sugars in soils incubated
with 1% glucose and 1% dextran. Soil Sci. Soc. Am. J. 351914-922.
Parr, J.F., and R.I. Papendick. 1978. Factors affecting the decomposition of trop
residues by microorganisms. pp. 1 OI -129. In: W.R. Oshwald [ed.]. Crop
residue management systems. Amer. Soc. Agron. Madison, WI.

---

27
Paul, E.A., and J.A. Van Veen. 1978. The use of tracers to determine thb
dynamic nature of organic matter. In: Trans. of the II th World Congress of
the Intern. Soc. of Soi1 Sci. 3:62-102.
Pinck, L.A., and F.E. Allison. 1957. Maintenance of soil organic matter. Bail Sci.
71:67-75.
Puig-Gimenez, M.H., and Chase F.E. “1984. Laboratory studies of facto%
affecting microbial degradation of wheat straw residues in soil. Cari, J.
Soil Sci. 64:9-19.
Reber, H., and A. Schara. i 971. Degradation sequences in wheat straw extra&
inoculated with soi1 suspensions. Soil Biol. Biochem. 3:381-383.
Reinertsen, SA, L.F. Elliott, V.L. Cochran and G.S. Campbell. 1984. Role of
available carbon and nitrogen in determining the rate of wheat straw
decomposition. Soi1 Biol. Biochem. 16:45946#4.
Salonius, P.D. 1983. Effects of air drying on the respiration of forest SO~I
microbial populations. Soil Biol. Biochem. 15: i. 99-203.
Santantonio, D., and J.C. Grace. 1987. Estimating fine-root production iand
turnover from biomass and decomposition data: A compartment-flow
model. Can. J. For. Res. ‘17:900-908.
Sauerbeck, ID. 1966. A criticall evaluation of incubation experiments on Fhe
priming effect of green-manure, pp. 199-207, In: Technical meeting on the
use of is’otopes in soi1 organic matter studies. Int. Atomic Energy A$ency,
V i e n n a . Austria.
Sauerbeck, D. 1968. Die umsetzung markieter orgaischer substanzen i/n boden
in abhangigkeit von art, Meng, und Rottgrad. Landwirtschaftliche
Forschung 21:91-l 02.

---

28
Sauerbeck, D., and M.A. Gonzalez. 1977. Field decomposition of carbon-l4-
labeled plant residues in various soils of the Federal Republic of
Germany and Costa Rica. pp. 117-132. In: Proceedings of the
international symposium of soil organic matter studies. Vol. 1: Int. Atomic
Energy, Agency, Vienna, Austria.
Schaller, F. 1968. Soil animals. University of Michigan Press, Ann Arbor, Ml.
Shields, J.A., E.A. Paul, and W.E. Lowe. 1974. Factors influencing the stability
of labeled microbial materials in soils. Soil Biol. Biochem. 6:31-37.
Siddoway, F.H., and C.R. Fenster. 1983. Soil conservation: Western Great
Plains. in: H E. Dregne and W. D. Willis [ed.]. Dryland Agriculture.
23:233-244.
Smith, J.H., and R.E. Peckenpaugh. 1986. Straw decomposition in irrigated soil:
comparison of twenty-three area straws. Soil Sci. Soc. Am. J. 50:928-932.
Steiner, J.L.,,H.H. Schomberg, and J.E. Morrison. 1993. Residue decomposition
and redistribution. In: Crop residue management technology transfer.
S. Plains. B. A. Stewart [ed.] USDA-ARS / SCS.
Stevenson, I.L. 1956. Some observations on the microbial activity in
remoistened air-dried soil. Plant Soil 8: 170-l 82.
~
Stott, D.E., G. Kassim, W.M. Jarrell, J.P. Martin., and K. Haider. 1983a.
Stabilizat’ion and incorporation into soil biomass of specific plant carbons
during biodegradation into soil. Plant Soil 70:15-26.
~
Stott, D.E., J.P. Martin, D.D. Focht, and K. Haider. 1983b. Biodegradation,
Stabilization in humus, and incorporation into soil biomass of 2,4-D, and
chlorocatechol carbons. Soil Sci. Soc. Amer. J. 47:66-70.

---

29
Stott, D.E., L.F. Elliott, R.E. Papendick, and G.S. Campbell. 1986. Low
temperature or low water potential effects on the microbial decomposition
of wheat residues. Soi1 t3iol. Biochem. 18577-582.
Stott, D-E., and J.P. Martin. 1989. Organic matter decomposition and retention in
arid soils. In: Arid Soil Research and Rehabilitation. 3:115-148.
Stott, D.E., and J.P. Martin. 1990. Synthesis and degradation of natural end
synthetic humic material in soirs. pp. 37-63. In:: [ed.] Humic substances in
soi1 and cxop sciences. Selected readings. Anner. Soc. Agron., and Soi1 Sci.
Soc Amer. J.
Stott, D.E. 1992. Mass and C loss from com and soybean residues as
associated with their chemical composition. Agron. Abst. p. 267.
Stott, D.E. 1993. Changing rel’ationship between mass and surface area of
decomposing residues. Agron. Abst. p. 261.
Stott, D.E., J-R.. Barrett. 1994. RESMAN: Software for simulating changies in
surface trop residue mass and caver. Paper submitted Soil Sci. Soc. Am.
J. (Sept. 1994).
Stotzky, G. 1967. Clay minerals and microbial ecology. New York Acad. of Sci.
Trans. (Series II) 30: 11-21.
Strozky, 6. j 980. Surface interactions between clay minerals and microbes,
viruses and soluble orgianics, and the probable importance of these
interactions to the ecology of microbes in soils. pp. 231-248. In: R.C.W.
Berkeley et al. [ed.] Microbial adhesion to surfaces. Ellis Horwood,
Chichester. UK
Stroo, H.F., KL. Bristow, L.IF. Elliott, R.I. Papendick, and G.S. Campbel/l. 1989.
Predicting rates of wheat residue decomposition. Soil Sci. Soc. Am. J.
53:91-99.

---

30
~ Summerell, B.A., and L.W. Burgess. 1986. Decomposition and chemical
composition of cereal straw. Soil Biot. Biochem. 21551-559.
Tanaka, D.L. 1986. Wheat residue loss for chemical and stubble-mulch fallow.
Soi1 Sci. Soc. Am. J. 50:434440.
Tian, G., B.T. Kang, and L. Brussaard. 1992. Biological effects of plant residues
with contrasting chemical compositions under humid tropical conditions-
Decomposition and nutrient release. Soil Biol. Biochem. 24:1051-l 060.
Vigil, M.F. and Kissel, D.E. 1991. Equations for estimating the amount of
nitrogen mineralized from trop residues. Soil Sci. Soc. Am. J. 55:753-757.
Wagner, G.H. and U.K. Mutatkar. 1968. Amino components of soil organic
formed during humification of 1% glucose. Soil Sci. Soc. Am. J. Proc. 32:
683-686.
Waksman, S.A. 1932. Principles of Soit Microbiology. Williams and Wilkins,
Baltimore, MD.
Wessen, B., and B. Berg. 1985. Long-term decomposition of barley straw
Chemical changes and in growth of fungal mycelium. Soil. Biol. Biochem.
18: 53-59.
Whitford, W.G., Stinnett, K, and J. Anderson. 1988. Decomposition of mots in a
Chihuahuan desert ecosystem. Oecologia 75:8-l 1.
~ Wilson, J.M., and D.M. Griffïn. 1983. The effect of water potential on growth of
some soil basidiomycetes. Soi1 Biol. Biochem. Il:21 l-21 2.
Zachman, J.E., and DR Linden. 1989. Eat-thworm effects on com residue
breakdown and infiltration. Soif Sci. Soc, Am. J. 53: 18461849.

---

3 1
CHAPTER 2
SURFACE RESIDUE AND ROOT DECOMPOSlTION OF CO-lTON, k’EANUT
AND SORGHUM FOR USE IN EROSION PREDICTION M0DBL.S
2.1. Abstract
Developing effective management strategies# that protect soi1 agairkt erosion
requires an understanding of residue decomposition. While the impakt. of
environmental factors such as temperature and water content has been studied,
little has been done to understand how the characteristics of the residk itself
impact the decomposition rat.e. Traditionally, the C:N ratio has been used as a
predictor of decomposition rates for agronomie crops, but has recentlyi been
shown to be poorly correlated. This study relates the chemical compdsition of
residue components (aboveground biomass and roots) to the decompbsition
rates for three cultivars each of three crops: cotton (Gossypium hitwtbn),
sorghum (S’orghum bico/or*) and peanut (Arachis hypogaea). The rat& were
determined by mass loss and CO1 evolution. Clhange in the specific surface
area of the residue as related to mass loss was also measured. The three
crops were from slowest to the most rapid loss: sorghum > cotton > peianut.
From the initial chemical and physical residue characteristics, the folldwing
equation was developed to predict decay in the first stage:
Pr‘ = (N*Sugars*Hemicellulose*&“.) / Lignin, where PD is the predictiveldecay
rate, KG,. is the initial specIifïc: surface area-to-mass ratio. For mass lo/ss, ? =
0.96, and for CO2 evolution, ? = 0.95. Since varietal differences within C~O~S

---

32
have led to significant variation in decomposition rates, cultivars with slower
~ decaying residues might be recommended for highly erodible lands.
2.2. Introduction
Soi1 erosion is a problem with many consequences. It cari limit soil
productivity, denude the landscape, transport sediments, organic matter and
pollutants from one place to another. Surface-managing trop residues is a
primary method of controlling soi1 erosion by water or wind.
In many areas of
the world, insufficient amounts of residue are produced to provide adequate
erosion protection. In ‘other areas, the accumulation of trop residues is
frequently viewed as a nuisance to trop establishment and growth, and a
disposa1 problem (Elliott et ai., 1987).
The root system of a trop is as important as surface residue in preventing
water erosion by limiting lateral runoff. In some areas there is not enough
surface residue due to low productivity, burning for management purposes, or
utilization as animal feed or even as fuel. In these areas, roots may be the only
type of residues lefi in the field. Consequently, while residue caver may not be
sufficient to protect surface soil, roots systems cari play a major role in reducing
sediment loss from water erosion.
The rate of residue decomposition Will determine the amount of soil surface
covered during critical erosion periods throughout the year, as well as the
amount of residues in top portion of the soi1 profile.
Therefore, understanding
the mechanisms of residue decomposition is necessary for developing a viable
trop residue management system for erosion control.
Plant residues consist of two parts: the aboveground portion, mainly
composed of stems and leaves, and the roots. The aboveground biomass may
be standing, flat on the soil surface, or become buried through tillage and other
management operations. The physical nature and the initial chemical

---

33
composition of the plant residues largely determine the ability of microbrganisms
to assimilate them. In the traditional agronomie, literature, the C:N ratib has
been assumed to be a controlling factor, while in the traditionai forestl
literature, the lignin-to-N has been considered rnost important. Howeqer, the
C:N ratio is apparently no,t the deterrnining factor, nor is the lignin-to-NI ratio
solely responsible (Stott, ‘1992).
Decomposition rate for plant residueivaries
between plant species and between cultivars wilthin a species (Stott, 1993).
Most klnowledge about trop residue decomposition is based on abbve-
ground residue, mostly wi’nter wheat (Brown and Dickey, 1989; Knapp iea al.,
1983; Tanaka, 1985; Stotf et: al., 1988 and 1990; Broder et al., 1988; &roo et al.,
1989; Col!ins et al., 1990; Douglas et al., 1992; ,Steiner et al., 1993), w/hereas
there have been few studies of decomposition of roots in any ecosysteim (Berg et
al., 1987; Elottner et al., 1988; Cheng et al., 1990). There may be sole
diffïculties iin following the decomposition of roots in the soi1 under nattiral
conditions.
An in sifu study of decomposition of rootderived carbon fdom wheat
revealed that the degradation of rootderived organic material present iin the
wheat. rtiirosphere was more complete in undisturbed soil than when dirdried
roots were mixed with moist or air-dry soil (Martin, 1989).
The specific-surface-area-to-mass ratio (k) represents a fraction of an area
(ha) of soil covered by one k.g of residue and is :specific for a ciop typd. The k
value is a conversion constant (ha kg-‘) used in an equation for convetiting
residue ma,ss to caver (Gregory, 1982):
C=l..p)
C2.1)
where:
C = fraction of the surface caver remaining
m = mass (kg ha-‘) of residue present on the surface
The Gregory equation is currently used in alX the USDA erosion mbdels:
WEPP (Water Erosion Prediction Project), WEPS (Wind Erosion Pred ction
i

---

34
System), RUSLE ( Revised Universai Soi1 Loss Equation), and RWEQ (Revised
Wind Erosion Equation).
The residue mass-surface caver relationship is closely related to the levels
of residues, and considerable decomposition of mass may occur before a large
decrease in caver is measured (Steiner et al., 1993).
For residues having high
proportion of leaf material following harvest, there may be tremendous loss in
mass with little loss in caver, because leaf material decomposes rapidly and is
light compared to stem material (Stott, 1992). Stern will lose mass, not surface
area.
The objectives of this study were to: (i) determine decomposition rates for
cotton, peanut and sorghum above-ground residues and roots by two methods:
COZ evolution and mass toss; (ii) determine how the initial physical and chemical
properties of the roots and residues impact the decomposition rates; (iii)
determine if differences in decomposition exist between plant varieties within a
species; (iv) determine changes in the mass-to-specifïc surface area during
decomposition; and (v) develop predictive decay equations for plant residues
based on mass loss or COS loss and the chemical and physical characteristics of
the residues.
2.3. Materials. and Methods
~
2.3.1. Soil
A Russell silt-loam (fine-silty, mixed, mesic Typic Hapludalf) soil was used in
this study. It was obtained from the Ap horizon at the Purdue Agronomy
Research Center in West Lafayette, IN. The soil was airdried (to minimize
microbial action before use), crushed to pass a 2-mm mesh screen, then stored
until use. The soil had a pH of 5.3, a total C content of 7.8 g kg*‘, and a total N
content of 1.2 g kg-‘.

---

35
2.3.2. Plant Materiais
Plant materials from three crops: cotton (Gossypium hirsutum), pearhut
(Arachis hypogaea) and sor’ghum (Sorghum bic&r) were used for this /
experiment.
Each orop was represented by three genetically different dultivars.
For each cultivar, the residue was split into two residue types (above-grbund
biomass ancl toots). These components were used to determine the re!sidue
decomposition rates.
Table 2.1. Dates and locations of the orop sample colleotion.
i.
Crops
Cultivars -
Sampling Dates
County
State
..---1....... --.---.
. ..L....-...- .-........e . ...” . . . . . . . . . . . . . . . . . . . . ..- - ..*.-.....*..---
Cotton
DLP-5690
911 oi93
Sumter Co.
“--e---
eorgia
D P - 5 2 1 5
8/1 oi93
Duval CO.
:
Texas
HS-46
9/13/93
Pike CO.
Alabama
Peanut
Florunner
9/10/93
Sumter CO.
Georgia
NC-7
9i25i93
Stoney Creek
IWrginia
NC-1 1
9i25i93
Stoney Creek
IVirginia
Sorghum
Triumph-266
7/14/93
Duval CO.
‘Texas
GW-744BR
1 Oil !Y93
Payne Co.
Gklahoma
NorthrupKing-300
11 i23i93
Saluda CO.
Si. Carolina
Plant residue sarnples were colleoted by USDA-SCS personnel fro#n fields in
several statles (Table 2.1), within one or two days of harvest in order to/ be in
unweathered condition and maximize their use. Five plant samples,
representatiive of the whole field, were taken as follows: one plant was /pioked
from the canter of the field, and the other four were oolieoted eaoh between one
corner and the oenter of the lïeld, avoiding the end rows. When remobing the
whole plant from the ground, oare was taken SO that the mots within thb top lO-
20 cm of the soil did not break apart.
The residues were

---

36
shipped overnight to the National Soil Erosion Research Laboratory (NSERL) in
West Lafayette, IN. The leaves and stems (above-ground biomass) were
separated from the roots. The residues were gently washed with water to
remove any remaining soit and airdried before chemical analysis.
23.3. Chemical Analysis of Plant Materials
Each plant residue component was chemically analyzed for total C content,
total N content, simple sugar content and the structural and non-structural
carbohydrate contents. Total C and N content were measured by dry
combustion (Mode1 CHN-600; Leco Corp., St Joseph, Ml). Hemicellulose,
cellulose, and lignin contents were determined by sequential fiber analysis
(Goering et al., 1970). This fiber analysis system was designed to provide
estimates of forage fïber composition.
For the sequential fiber analysis, four different solutions, neutral detergent
fiber (NDF), acid detergent fïber (ADF), demineralizing solution, and a potassium
permanganate solution were used. The neutral detergent solution was made
from sodium lauryl sulfate, ethyl diamine tetra acetic, sodium phosphate dibasic,
and water; the acid detergent solution was prepared from hexadecyl trimethyl
ammonium bromide, sulfuric acid, and water; the demineralizing solution was a
solution of oxalic acid, and the saturated potassium permanganate solution was
obtained from potassium permanganate plus silver sulfate mixed with water.
Following is a brief description of the steps involved in the sequential fïber
analysis.
First, a 0.5-g of ground residue was placed into a Berzelius beaker,
and 100 ml of neutral detergent solution was added for digestion on a hot plate
for 1 hr. A 4.25 cm glass microfiber filter (Whatman GF/A) was placed into a
standard sintered glass crucible (Pyrex 50 ml, C porosity). Neutral detergent
fïber residues were then filtered under vacuum onto the glass filter-crucible
combination, dried at 105’C for 24 hr, cooled for 20 min in a dessicator, and

---

37
weighed.
The glass fïlter plus NDF residue was removed from the cruc&ble and
piaced into another Berzelius beaker for the ADF digestion.
Remaining residue
from the NDF analysis adhering to the crucible wall was removed with 4 rubber-
tipped glass rod and ADF solution and added to the beaker. The glas$ filter
and NDF residues in the beaker were broken up using the rubber-tip glbss rod.
Acid detergent solution was then poured into the beaker up to 100 ml fc/r the
digestion of the residue. The same procedure described above for N& was
followed for ADF determinatioln in the second step. In the third step, tde
crucible containing ADF residue was placed into a shallow pyrex pan. ‘About
113 to 2/3 cm of water was added to the pan. Enough of the permangdnate
mixture was added to the a*ucible to wet the sample. The residue wasl again
broken up with the glass rod im the crucible. Them the crucible was alldvded to
stand for 1.5 hr, while stirring every 15-20 min, and adding more of the !mixture if
neczssary. After filtration, the crucibie is placed in a clean pyrex pan 8nd filled
half fulY with demineralizing solution. After rinsing the residue several iimes with
the dernineralizing solution. the finished fiber should be white. Then, the
crucible was washed 3-4 tirnes with ethanol80%.
The white residue das dried
at 105’C overnight, cooled for 20 min in a dessicator, and weighed.
Afierwards,
the crucible ‘was put into a muffle furnace, at 500°C for the ash determihation.
After 4 hr, the crucible was removed from the muffle fumace, put back ih the
1 OSoC oveni ovemight, coolled in a dessicator Andy weighed. NDF was kalculated
as the ratio between the sample weight after digestion with NDF soluticjn and the
initial sample weight times the sample dry matter; ADF was the ratio b&een the
sample weight after digestion with ADF solution and the initial sample *eight
times the sample dry mattel-; hemicellulose was determined as the diffdrence
between NDF and ADF; lignin content was assumed to be known as the
remaining of the residue sample after digestion; c&llulose was determirjed as the
difference between lignin and ash (Chemey et ai., 1985).

---

38
Two plant monosaçcharides, or simple sugars, sucrose and fructose were
measured colorimetrically.
Sucrose analysis (Handel, 1968) was determined
by placing into a small test tube, a 100 ~1 aliquot extracted from a 1:l weight-
volume ratio of finely ground residue and 50% ethanol solution. 100 ~1 of 30°k,
KOH was added to destroy the sugars.
Then the test tube was placed into a
boiling water bath for 10 min, and cooled to room temperature. Ptior to mixing
on vortex-type mixer, 3.0 ml of anthrone reagent was added. The samples were
Yncubated at 40°C for 15 min before reading the absorbante on a
spectrophotometer set at 620 nm.
‘Fructose analysis (Davis et al., 1967) was determined using 100 FI aliquot
from the same extract that was used to determine sucrose. TO each sample,
3 ml of conoentrated HCI was added plus 1 ml of O.O5*r6 resorcinol reagent.
The sample was well mixed on a vortex-type mixer, and incubated in a Mer
bath set at 77’C for 8 min. Then the samples were allowed to cool to room
temperature just prior to measuring absorbante at 420 nm on the
spectrophotometer.
2.3.4. Plant Residue Mass loss Experiment
The mass loss experiment consisted of a randomized complete block design
with one soil, three crops, three cultivars for each trop, and two residue types
(above-ground biomass and roots) for each cultivar.
The treatments were done
in triplicate.
Each treatment consisted of leaves and stems in the same proportion as was
present in the aboveground biomass after harvest. Roots were incubated
separately (Table 2.2).

---

39
Table 2.2. Plant residue corrponents and loading rates.
_,__.._....._.._.._...............................................
- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..-..........................-..................-......
. . .._.. * .____..___....
(%)
(g/l OOg soil)
(%)
(g/l OOg soil)
(%) (g/lOOig s o i l )
Cotton
45.0
0.90
55.0
1.10
100
2.bo
Peanut
26.5
0.57
71.5
1.43
100
2.po
Sorghum 412.5
0.85
57.5
1.1!5
100
2.bo
Residues were chopped into 4 to 5-cm long and the pieces were spr&d
evenly on the soit surface in a 10 by 7.5 cm2 polystyrene dish.
Optimudl
moisture conditions were assumed to be the water content at -113 bar wa/er
potential as equalled to 60% water holding capacity, plus 300% of the re$idue
mass’ (Myrold et al., 1981). Afler the appropriate amount of water was a/ded,
the incubation dish was loosely wrapped with a foocl service film (PYA /
Monarch, Inc., Greenville, SC), to allow some aeration. The samples wdre
incubated at 22’C f IOC.
Samples were withdrawn on day 3, 7, 14, 28, 56, and 84 of the incubption for
mass measurement. At each destructive sampling, the incubation mixtuie were
aven-dried at 40°C, for 48 hr. When dry, the residues were carefully separated
from the soil, gently washed ‘io iremove the soil par-ticles, and put back into the
oven at 40°C for 48 hr. The residues were weighed then placed into crubibles
for ashing at 8OO’C for 2 hr.
The equations used to calculate the percent mass remaining were:
MT=M~-M/,
(2.2)
%MR=(MT/M,)*lOO
(2.3)
where:
MT = corrected mass (g) remaining at time T
MF = mass (g) of the residue after incubation (oven dry basis)

---

Mr, = mass (g) of the ashed residue
;
MR = % of initial mass remaining at day T
~ M, = initial residue mass ‘(9)
T is the incubation time in days
I
2.3.5. CO, Evolution
A second method for determining decomposition rate is to measure the
amount of C evolved as CO*. TO monitor microbial respiration, a known mass of
residue, chopped into 4 to 5-cm lengths was spread evenly on 100 g airdried
soi1 in an incubation jar. Addition of an amount of water to achieve the water
content at -1/3 bar water potential as equalled to 60% water holding capacity
plus 300% residue mass (Myrold et al., 1981) gave optimum moisture conditions
of residue decomposition. An alkaline trap, 5 ml of a 30°h KOH plus tropaelin 0
as indicator, in a 25ml beaker was placed in each jar on top of the soi1 and
residue. Tropealin 0 (Sigma Chemical CO, St. Louis, MO) was used to check if
the KOH solution has reached a 50% CO2 saturation (pH 11). Respired CO,
was absorbed in the KOH trap.
Each jar was placed into a circulating water bath, set at 22’C + l°C, and
hooked to an electrolytic respirometer. At the top of the respirometer, there was
a 25 or 50-ml burette, e positive electrode for oxygen, and a 4cm tube for
overflow. At the bottom, there was a negative electrode for hydrogen. Bath
electrodes were platinum. The positive electrode was connected to a 5OOml
chamber containing the electrolyte solution 8% (Na)*SO,. KOH was withdrawn
after 3 , 7 ,14 ,28 ,56 and 64 days of incubation. TO remove all of the KOH, a
22-gauge needle with a Luer-lock fitting was inserted into the jar stopper and
lengthened with a piece of capillary tubing to reach the bottom of the KOH trap.
Fresh KOH was injected in the same manner. The amount of CO, trapped in

---

41
the KOH was measured by a potentiometric method (Golterman, 1970); using an
automatic titrator (Mode1 DL :25, Mettler instrument Corp., Hightstown 4J).
The CO2 evolution experiment used the same statistical design as \\he mass
loss experiment with the addition of a control treatment (no residue). p correct
the amounl: of COZ evolved from the residues, CO2 evolution from the tiare soi1
(control treatment) was sustracted from COn evollved from treatments ($oil plus
residue) at each given time.
The reactions involved in KOH trapping the evolved CO2 are as follow$:
KOH 4. CO, ---> HCO, + K+
(2.4)
HCO, + K+ + HCI -> H,CO, + KCI
P-5)
Each milliequivalent of ‘KOH used to absorb evolved CO, is equivalent ito 12 mg
of CO, carbon. The formula used to calculate % C-CO, evolved is:
SC-CO,=[ Kl *(l/M)*V*N*Ci]
(2.6)
where:
K, = 0.135, a calculated vbnstant to convert the raw result into the desibed unit
M = the mass (g) of the residue
V = the volume (ml) of HCI titrant
N = the conlcentration (N) of HCI titrant
Ci = the initial carbon content (Oh) of the residue
2.3.6. Measurement of Specific Surface Area-ta-Mass Ratio
Specific sut-fa* areas ,for the leaves and stems were measured usbg a
digitizer (Summagraphics) arnd AutoCad version ‘10. As decompositid
proceeded, the ratio between the specific surface area and the mass r+maining
was calculated at each sarnpling time.

---

42
:
The equation used to convert residue mass to caver is from Gregory (1982):
C = 1 _ etekn)
(2.7)
~
where:
I
C is the fraction of the surface caver remaining
~ m is the mass (kg ha-‘) of residue present on the surface
The constant k cari be derived from the following equation:
k = - log(l-C) / m
(2*8)
~
2.3.7. Statistical Analysis
Statistical analysis of the data was done to deterrnine differencas among
~ treatmenfs, using the PC-SAS, Version 6.09 (SAS Inc., Cary NC). Comparisons
between treatment means were made at the P =0.05 levei using the Waller-
~ Duncan’s multiple range t,est procedure.
2.4. Results
~ 2.4.1. Initial Chemical Composition
The mean concentrations of total C and N, simple sugars, hemicellulose and
lignin {Tables 2.3 and 2.4) were significantly different between the above-ground
residues and roots for cotton cultivars DLP-5690 and DP-5215 For DLP-5690
above-ground residues, the total N content was 288Oh greater than the roots,
whereas total carbon, simple sugar, hemicellulose and Iignin contents were 3,
30,22 and 17% lower, respectively. For DP-521 5 aboveground biomass, total
N was 147% higher than the mots, whereas total carbcn, simple sugar,
hemicellulose and lignin contents were 5, 40, 49 and 51 O16 lower respectivefy.
Cultivar HS-46 above-ground residues had 232Or6 greater total N concentration
than the roots, but total C was 0.3% lower, hemicellulose 8Oh lower, and lignin

---

43
15% lower. Simple sugar concentrations of the above-ground biomasj; were
177% lower than the roots.
Far peanut, the initiai themical composition (Tables 2.3 and 2.4) of the
aboveground residues were signifïcantly different from the roots, except for total
C. Cultivar Florunner above-ground biomass had 88% higher simple sugar
concentrations than the roots, but total N was 44?/0 lower , hemicellulose 26%
lower, and lignin 32O16 lower. For cultivar NC-7 above-ground residue$, simple
sugar contents were 31 Oh greater than the roots, but total N was 44Ok, Ibwer,
hemicellulose 65% lower, and lignin 32O/c, lower as well. Cultivar NC-41 above-
ground biornass had 27% higher simple sugar concentrations than the!roots, but
hemicellulose and lignin were lower by 56% and 35% respectively.
Table 2.3. Initial chemical composition of the above-ground residues.
Crop
Cultivar
T o t a l C T o t a l N Sugars Hemicellulo$e
Lignin
g kg” residue
-
Cotton - OLP-5690
448.9 a’
31.4 a
18.1 c
252.4 b i-
112.1 a
DP-521 5
437.1 b
19.3 b
23.1 b
133.1 c
80.7 c ’
HS-46
457.3 a
30.9 a
34.0 a
262.5 a
103.3 b
Peanut
Florunner
450.4 a
13.4 b
89.9 a
176.6 a
64.8 a
NC-7
455.2 a
20.0 a
87.7 a
140.0 b
42.3 c
NC-1 1
450.4 a
ia.8 a
66.8 a
108.2 c
50.4 b
Sorghum Triumph-266 438.2 c
11.9 b
441.1 b
208.3 c
47.6 a
GW7-44BR
452.5 a
17.8 a
32.5 ç
327.1 a
32.5 b
NKing-300
447.9 b
6.9 c
,48.7 a
273.7 b
48.2 a
‘Values followed by the same letter, within speciies, are not signifïcantiy different
by the Waller-Duncan’s mAipIe range test at P = 0.05.

---

44
Sorghum above-ground residues and roots (Tables 2.3 and 2.4) were
significantly different in initial total C and total N, simple sugar, hemicellulose ,
and lignin concentrations. For cultivar Triumph-266 above-ground residues,
total N content was 86% greater than the roots, hemicellulose was 22O/6 greater,
but simple sugar and lignin contents were 37% and 41 OA.I lower than the mots
respectively.
Cultivar GW-744BR above-ground biomass had total N and
hemicellulose concentrations of 76 and 9% greater than the roots respectively,
but simple sugar and lignin contents were 76 and 41°h tower respectively.
For
cultivar Nking-300 above-ground residues, total C content was i5% higher than
the roots but total N, simple sugar, hemicellulose, and lignin concentrations were
22, 67, 14 and 44% lower respectively.
Tables 2.3 and 2.4 indicated significant differences in initial chemical
composition between cultivars within species.
I
Table 2.4. Initial chemical composition of the plant roots.
Crop
Cultivar
Total C Total N Sugars Hemicellulose Lignin
~ . ..-~.- . . . . . . _ . . . . . . . ..- - -..... - ___I-...._................-.........-~

_ . . . . . . . -.
. ..-.*.-.-..-.e.-
gw residue
Cotton
DLP-5690
463.2 a 8.1 ab’
26.0 c
322.6 a
135.7 b
DP-521 5
458.9 a
7.8 b
38.5 b
261.2 c
163.1 a
HS-46
458.9 a
9.3 a
94.3 a
283.5 b
121.5 c
Peanut
Florunner
452.4 a
24.0 b
47.7 b
238.8 c
95.3 a
NC-7
436.8 b
26.8 b
66.7 a
398.9 a
61.9 c
NC-1 1
456.3 a
31.3 a
68.5 a
247.5 b
77.3 b
Sorghum
Triumph-266
404.5 a
6.4 b
65.6 c
266.8 c
80.7 b
~
GW-744BR
346.0 c
10.1 a
132.7 b
360.2 a
55.1 c
NKing-300
388.0 b
8.9 a
148.8 a
317.6 b
86.5 a
‘Values followed by the same letter, within species, are net signficantly different
~ by the Waller-Duncan’s multiple range test at P = 0.05.

---

45
2.4.2. Initial Specific Surface Area
For cotton, the specifïc: surface area (Table 2.5) of the leaves and $terns
before the incubation did rot significantly differ between the cultivars. ‘The
specifk surface area of DL.P-5690, DP-5215, and HS-46 leaves was 141, 73 and
85% greater than the stems respectively.
No peanut cultivar was significantiy different from one another for tbe above-
ground specifïc surface araa (Table 2.5). The specific surface area of/the
/
leaves was significantly greater than the stems by 95O16 for Florunner, 135% for
NC-7, and 1113% for NC-l 1.
The initial specific surface area of the sorghum leaves and stems (fable 2.5)
showed significant differences between cultivars except for GW-744Bd.
Triumph-266 leaf specifk surface area was greater by 45% than that of Xhe
stems.
GW744BR leaf specifïc surface area was not signifïcktly diffkrent from
that of the stems. Nking-300 leaf specific surface area was 87Or6 highlr than
that of the stems. The leaf specifïc surface area for Triumph-266 was /aIso 18Ok
greater than that of GW-744BR, but go16 lower lower than that of Nking@O.
GW-744BR leaf specific surface area was 23% lower than that of NKin/g-300.
2.4.3. Initial Residue Mass
For all species, the stem mass was much greater than the leaves (Fable
2.5). Within cotton species, cultivar HS-46 above-ground residue mals was
higher than those of cultivars DP-5215 and DP-5690. No difference +s noted
between the initial mass of thie roots of these three cultivars.
For peanut, there was na1 significant difference in either the above/round
residue or tlhe root mass b,vtween cultivars Florunner, NC-7 and NC-1 4.

---

Sorghum cultivar GW-744BR presented greatet above-ground residue mass
than Triumph-266 and Nking-300. However, GW-744BR root mass was îower
than those of Triumph-266 and Nking300 which were not different.
Table 2.5. Relative initial mass and specifrc surface area of the residue components.
. . . . . . . . . . . .
. -._..--
. . . . . . ..-.......-..................
-...:-
-_-___....___I__._-....
--
--------~
Crops
Cultivars
1 Relative Initial mass (%) i
Relative Initial 1
i specifïc surface I
area
(96)
i
i Leaves Stems
Roots ] Leaves
Stems i
I
Cotton
DLP-5690
j 38.5 a’
43.9 ab
17.6a 1 66.8 a
33.2 a i
DP-5215
i 34.4 b
49.1 a
16.5a i 63.4a
%.6a 1
HS-46
40.8 a
45.9 ab
13.3b 1 64.9a
35.1 a i
;
._ . . . . . . . .
. ..-..- . . . . . . . . . .- ..-.. +.“.-.-.
~-1.-.-
Peanut
Florunner
i 24.3 b--s”~~~~e”--&~a
j 65.4 b
33.6 a i
NC-7 f 27.8 ab 67.5 ab
4.7 a i 77.0a
23.0 b j
NC-I 1 i 29.4 a 65.1 b
5.5 a i 68.0 b
32.0 a i
Sorghum Triumph-266 ; 36.9 a 44.5 b
18.6 a i 59.2 b
40.8 b j
GW-744BR i 33.2 b 52.5 a
14.3 b 1 50.2 c
49.8 a f
NKing-300 i 36.2 a 46.9 b
16.9 ab ] 65.1 a
=.gc
/
” . ..-.*.
-.....-.--.....---^ A...- -..-.-. ----._-
‘Values followed by the same letter, within species, are net signifïcantly different
by the Waller-Duncan’s multiple range test at P = 0.05.
2.4.4. C lest as CO2
One method of determining residue decomposition rates is to measure the
amount of C evolved as COz after correction for the amount evolved from bare
,

!soil. For cotton residue, C evolved as COS increased rapidly during the first
l
fourteen days of incubation then started leveling off from day 15, and then
l
showed no significant change after 28 days until the end of the expetiment.

---

Cultivar OLP-5690 above-ground biomass (Figure 2.1) showed cumulative C lest
as COa, after 14 days, 35% which was significantly greater than the 22% evolved
from the roots. For cultivar DP-521 5 above-ground residues (Figure 2.f!), C
lost, 30%, was greater than that of the roots, 10%. Cuftivar HS-46 (Figure 2.3),
showed no :significant difference in cumulative CO2 evolved between the above-
ground biomass, 30%, and the roots, 27%.
The decamposition rates differed among the Icotton cultivars. DLP-5690
(Figure 2.4) above-ground residues were degraded faster than DP-5215 and
HS-46 above-ground biomass.
The latter two cultivars did not degrade at
significantly different rates. Cumulative COz evolution of the roots for DILP-
5690, DP-5215 and HS-46 (Figure 2.5) induced a different scenario with cultivar
HSA6 root decay rate (Table 2.6) being fastest followed by OLP-5690 roots, and
DP-521 5 presented the slowest decomposition rate.
The total carbon evolved from the peanut cultivars Florunner, NC-7 and NC-
11 above-ground residues (Fiigures 2.6, 2.7, and 2.8) was rapid during the first
14 days, 57, 53 and 50% respectively. The C losses were signifïcantly higher
than the roots, 15, 10, and 7% lost, respectively. F’lorunner above-ground
residues were signifïcantly greater in C loss than that of NC-7 and NC-1 ‘1
(Figure 2.9). Also, Florunner roots (Figure 2.10) were signifïcantly different than
that of cultivars NC-7 and NC-l 1 in C evolved as COz.
As a result, the decomposition rate of Florunner above-ground residues
(Figure 2.9) was significantly higher than NC-7 and NC-1 1 above-grouncl
residue decay rates, and Florunner root degradability (Figure 2.10) were
significantly greater than that of cuftivars NC-7 and NC-l 1 roots.
Sorghunn cultivars Triumplh-266 and GW-7448R showed significant
difference in % C evolved as COz in the first 14 days (Figures 2.11, and 2.12)
between the above-ground, 23 and 45% CO& respectively, and the roots, 18
and 34% CC)&, respectively.. For cultivar Nkingl-300 above-ground residues,
(Figure 2.13), the cumulative % C lost as CO2 was lower, 33% than that of the

---

48
roots, 40%. Consequently, GW-744BR above-ground residues (Figure 2.i4)
and Nking300 roots (Figure 2.15) had fastest decomposition rate whereas
Triumph-266 and GW-744BR roots were decomposed very slowly (Table 2.6).
Peanut above-ground residues decay rate (Figure 2.16) decomposed
significantly faster than cotton and sorghum. Cotton and sorghum above-
ground biomass decomposition rates were not significantly different from one
another. Sorghum roots have a faster decay rate than either cotton or peanut
roots (Figure 2.17).

---

49
100
90
--
-
Aheground
80
- - R:o~t
- E%are soi1
-
-
70
60
50
40
30
20
10
0
10
10
20 30 40 50 60 70
80 90
Time (days)
Figure 2.1 Decomposition of cotton DLP-5690 as rmeasured by CO2 evolution
over time.
Bars represent standard deviations at given time. CO2
evolved from the bare soi1 was used to correct the CO2 evoluti,on from
treatments with residues.

---

50
100
90
i
-Aboveground ’
80
- - Root
70
60
50
40
30
20
10
0
0
10 20 30 40 50 60 70 80 90
Time (days)
Figure 2.2. Decomposition of cotton DP-521 5 as measured by COz evolution
over time. Bars represent standard deviations at given time.

---

51
100
90
-----
/
! --Aboveground 1
80
i
- -’ Root
-
-
----A
70
60
50
40
30
20
10
0
0
10
30 40 50 60 70 80 90
Time (days)
Figure 2.3. Decomposition of cotton HS-46 as measured by COz evolution over
time.
Bars represent standard deviations at given time.

---

52
100
90
- DLP-5690
80
- D P - 5 2 1 5
1-c HS-46
70
60
50
40
30
20
10
0
0
10 20 30 40 50 60 70 80 90
Time (days)
Figure 2.4. Decomposition of cotton above-ground biomass as measured by CO2
evolution over time. Bars represent standard deviations at given
time.

---

100 y-
90 -
- - I
-ii’L-5690
80 -
- DP-5215
70 -
- - HS-46
-
-
-
- - -
60 -
50 -
40 -
30 -
20 -
10
0
0
110
201 30 40 50 60 70 80 90
Time (days)
Figure 2.5. Decomposition of cotton roots as measured by CO2 evolution over
tirne. Bars rep:resent standard deviations at given time.

---

54
400
90
-Aboveground ;
0 80
70
60
50
40
30
20
10
0
0
10 20 30 40 50 60 70 80 90
Time (days)
Figure 2.6. Decomposition of peanut Florunner as measured by CO2 evolution
over time. Bars represent standard deviations at given time.

---

i
100
90
-Aboveground
80
-
-i
70
60
50
40
30
20
10
01
0
10 Z!O
30 40 50 60 70 80
90
Time (days)
Figure 2.7. Decomposition of peanut NC-7 as measured by COz evolution over
time.
8ars represent standard deviations at given time.

---

56
100
90
80
70
60
50
40
30
20
10
0
0
10 20 30 40 50 60 70 80 90
Time (days)
Figure 2.8. Decomposition of peanut NC-l 1 as determined by CO2 evolution
over time. Bars represent standard deviations at given time.

---

57
100 I
-
90
80
70
60
50
40
30
--
f - Florunner ’
20
- - N C - 7
10
! - D- NC-I?
1
0
’
’
’ 1--1--J
0
10 20 30 40 50 60 70 80 90
Time(days)
Figure 2.9. Decompositior: of peanut above-ground biomass as measured by
1CO2 evolution over time. Bars represent standard deviations at
given time.

---

100 t
90 -
- Fiorunner
80 -
1.-NC-7
70 -
- - NC-11
60 -
50 -
40 -
30
20 F
0
10 20 30 40 50 60 70 80 90
Time (days)
Figure 2.10. Decomposition of peanut roots as measured by COS evolution over
time.
Bars represent standard deviations at given time.

---

59
L
90 -
----
r -,r\\boveground
80 -
- - IRoot
-----.-~. -. ._
70 -
60 -
50 -
40 -
30
20
10
0
0
10 210 30 40 50
60 70
80 90
Time (days)
Figure 2.11~ Decomposition of sorghum Triumph-266 as measured by CiO,
evolution over time. Bars represent standard deviations at given
time.

---

61
[-Aboveground 1
80 t
I- * Root
70 -
60 -
50 -
40 -
30 -
0
10 20 30 40 50 60 70 80 90
Time (days)
Figure 2.13. Decompos’ition of sorghum NKing-300 as measured by CO2
evolution over time. Bars represent standard deviations at given
time.

---

62
100
90
- b CàW744BR
80
70
60
50
40
30
20
10
0
0
10 '20 30 40 50 60 70 80 90
Time (days)
Figure 2.14 Decomposition of sorghum above-ground biomass as measured by
COz evolution over time. Bars represent standard deviations at
given time.

---

63
‘O0
90 -
- Triumph-266 1
80 -
- * GW744BR ’
70 *
- NKing-300 /j
60 -
50 -
40 -
20
10
0
0
10
30 40 50 60 70 80 90
Time (days)
Figure 2.15. Decomposition of sorghum roots as measured by COZ evolution
over time. Bars represent standard deviations at given time.

---

100
90
80
70
60
50
40
30
--
,
20
- Sorghum i
- C Peanut )
10
0
0
10 d20 30 40 50 60 70 80 90
Time(days)
Figure 2.16. Mean decomposition rate of the above-ground biomass for each of
the three crops as measured by CO2 evolution over time.
Bars
represent standard deviations at given time.

---

65
.P
. .
:
.:
P
:
.”
- * Peanut
- ii.5040
-60
., i
30
20
r* - - L - a
10
0
0 10 20 30 40 50 60 70 80 90
Time (days)
Figure 2.17. Mean decomposition rate of the roots for each of the three crops as
meksured by COz evolution over time. Bars represent standard
deviations at given time.

---

2.4.5. Change in Mass loss
In determining mass ~OS!;, the above-ground residues were split in leaves
and stems and each of these components was measured separately.
For cotton
cultivars (Figures 2.18, 2:19 and 2.20), the rate (of mass loss of the leaves was
significantly higher than the stems and roots. However, no significant difference
was found between stems and the above-ground biomass in any of the three
cultivars. DLP-5690 (Figure 2.21) had a faster above-ground residue
breakdown rate, 38%, followed by that of DP-5215, 30% and HS-46, 26%. HS-
46 rqot mass loss (Figure 2.22) was higher, 29%, than that of DLP-5690 and DP-
5215, 24 and 17% respeciively.
Peanut leaf mass loss was significantly faster than that of the stems which
were much faster than rocts (Figures 2.23, 2.24 and 2.25) for all cultivars.
Cultivars Florunner and NC-‘7 showed no significant difference between, stems
and the total above-ground in the percent mass remaining during the first 14
days.
Only NC-1 1 presented higher mass loss for the leaves, 43%, than stems
and roots, 126 and 9% respectiv,ely.
There was no difference in rate of
breakdown of the above-ground residues between the three ciltivars (Figures
2.26), but Florunner root t-lad a faster mass loss rate than the roots from the
other two cultivars (Figure 2.27).
Sorghum cultivars showed significant differences between the above-ground
residues and the root breakdown (Figures 2.28, 2.29, and 2.30) in the earfy
decomposition.
However, only cultivar Triumphi-266 presented a signifïcant
difference between leaves amd stems. There was no difference in decay rates
between the above-ground residues for the three cultivars (Figure 2.31).
Signifitant differences in mass remaining were observed between the mean
mass loss of the cultivars of cotton, peanut, and sorghum above-ground biomass
(Figure 2.33) in the early decomposition phase. Peanut mass loss was greater,
45%, than cotton and sorghum, 33 and 25%, respectively.
However, sorghum

---

67
root breakdown (Figure 2.34) was faster, 12%, than that for cotton and peanut
roots, 7 and 5%, respectively.

---

68
100
90
80
l-
70 -
60 -
50
-
40
-
r
- - stem
20
-Aboveground
10,
- Rcaot
0
10 20 30 40 50 60
Time (days)
Figure 2.18. Decomposition of cotton DLP-5690 as measured by mass loss
over time. Bars represent standard deviations at given time.

---

69
100
90
80
70
60
\\
40
.
z
I
30 i - Leaf
- - Stern
-Aboveground
- Root
0
10 20 30 40 50 60
70 80 90
T i m e ( d a y s )
Figure 2.19. Decomposition of cotton DP-521 5 as measured by mass loss over
time. Bars represent standard deviations at given time.

---

70
90
88
70
-
T
60
50
40
30
20
10
o
10 20 30 40 50 60 70 80 90
Time (days)
Figure 2.20. Decomposition of cotton HS-46 as measured by mass loss over
time.
Bars represent standard deviations at given time.

---

71
80 -
70 -
60 -
50 -
40 -
30 -
- DLP-5690
20 -
- D P - 5 2 1 5
10
- - H S - 4 6
1
o
10
20 30 40 50 60 70 80 90
Time (days)
Figure 2.21. Decomposition of cotton above-ground biomass as measured by
mass loss.over time. Bars represent standard deviations at given
time.

---

72
100
90
80
70
60
50
40
--v
30
- DLP-5690
- - DP-5215
20
10
0
0
10 20 30
40 50 60 70 80
90
Time ldavs)
Figure 2.22. Dec:omposition of cotton roots as measured by mass loss over
time.
Bars represent standard deviations at given time.

---

73
100
90
80
70
60
50
40
30
- L e a f
20
- * Stern
-Aboveground 1
10
- R o o t
0
0
10 20 30 40 50 60
70 80 90
Time (days)
‘Figure 2.23. Decomposition of peanut Florunner as measured by mass loss
over time. Bars represent standard deviations at given time.

---

74
70 -
60 -
50 -
40 -
30 -
20 - -Aboveground
10 -
0
10
20 30 40 50 60
70 80
90
Time (days)
Figure 2.24. Decomposition of peanut NC-7 as rneasure,d by mass loss over
time.
Bars represent standard deviations at given time.

---

(%)

Residue Mass Remaining
L

---

76
70 -
60 -
50 -
40 -
30 -
I 0 Florunner1
20 -
10 -
0
10 20 30 40 50 60 70 80 90
Time (days)
Figure 2.26. Decomposition of peanut above-ground biomass as measured by
mass loss over ltime. Bars represent standard deviations at given
time.

---

77
100
90
80
70
60
50
40
30
- Florunner
- - NC-7
20
-NC-l1
10
0
o
10. 20 30 40 50 60 70 80
90
Time (days)
Figure 2.27 Decompo.sition of peanut roots as measured by mass loss over
time.
Bars reoresent standard deviations at oiven time.

---

L _ _ _

- _ _ -

. I . _ . . . _ _ - - . I .

_ -
~ . . _

. ~ - . -

- _ _ .
78
100
90
80
70 L
i0 -
50 -
- II --P
40 -
-
--
30 - - Leaf
- - ’ Steim
20 -
-Aboveground
- Root
30 40 50 60 70 80
90
Time (days)
Figure 2.2;3. Decomposition of sorghum Triumph-266 as measured by mass
:
ioss over time. Bars represent standard deviations at given time.

---

79
100
90
80
70
60
50
40
30
- L e a f
- - Stern
20
-Aboveground
10
- R o o t
-
0
10 20 30 40 50 60 70 80 90
Time (days)
Figure 2.29. Decomposition of sorghum GW-744BR as measured by mass IOSS
over time. Bars represent standard deviations at given time.

---

100
90
80
70 -
60 -
50 -
40 -
~_-- -_II--_
30 -
- Leaf
- * Stern
20 -
-Aboveground
- fioot
10 -t
0 10 20 30 40 50 60 70 80 90
Time (days)
Figure 2.30. Decomposition of sorghum Nking-300 as measured by mass loss
over time. Bars represent standard deviations at given time.

---

100
90
80
70 -
60 -
5 0
-
40 -
30 -
20 -
10
-
0
10
20 30 40 50
60 70 80
90
Time (days)
Figure 2.31. Decomposition of sorghum above-ground biomass as measured by
mass loss over time. Bars represent standard deviations at given
time.

---

82
100
90
80
70 -
60 -
50 -
40 -
30 -
-4 Triumph-266
-‘GW44BR
20 -
- * NKing-300 /
10 -
30 40 50 60 70
80
90
Time (days)
Figure 2.32. Decomposition of sorghum roots as measured by mass loss over
time.
Bars represent standard deviations at given time.

---

83
100
90
80
70
60
50
40
30
-Cotton
20
- Peanut
10
S- o-r g h u m 1
0
0
10 20 30 40 50 60 70 80 90
Time (days)
Figure 2.33. Mean decomposition rate of the above-ground biomass for each of
the three crops as measured by mass loss over time. Bars
represent standard deviations at given time.

---

84
90
80
70
60 /
-*Cotton
= * Peanut
- Sorghumj
-.-
30 40 50 60 70 80
Time (days)
Figure 2.34,. Mean decomposition rate of the rwts for each of the three crops as
measured by mass loss over time. Bars represent standard
deviations at given time.

---

85
2.5. Discussion
The decomposition rates for ail cotton (Figures 2.1, 2.2, 2.3, 2.4, and 2.5)
peanut (Figures 2.6, 2.7, 2.8, 2.9, and 2.10), and sorghum (2.11, 2.12, 2.13,
2.14, and 2.15) cultivars followed the pattern for Michaelis-Menten first-order
kinetics.
The rapid increase in CO2 evolution during the first 14 days was
probably due to the high total N content, the high fevel of readiiy available C in
the form of extractable sugars or a combination of the two (Tables 2.3 and 2.4).
Kinetically, the CO* evolution from the residues studied exhibited a lineaf
dependence on the chemical composition of the residue. The rapid
disappearance of these soluble compounds we& probably related to a quick
buiid up of the microbial activity which would increase the CO2 respiration.
Also, the readily availabie C and N components in the trop residues might
provide the initial energy and nutrients necessary to activate the microorganisms
that are responsible for the degradation of the less readily available components
of the residue.
The leveling off phase of the COz evolution, between days 15 and 28, would
be the period where hemicellluiose was the main fraction available to the
microofganisms.
As the decomposition process proceeds, CO* evolution slows
down, following an exponential curve, probably due to change in chemicai
composition of the remaining residue available to the microorganisms.
I think
that in this phase of decomposition, the hemicellulose fraction probably
disappears initially at a rapid rate, but the subsequent degradation appeafs to
be slower. The degradation of hemicellulose is more marked when the
environment is aerobic, and when there is availability of inorganic nutrients,
especially nitrogen, (Alexander, 1977). At this stage of the decomposition
process, I think that there is probably not enough N or readily available C to
keep the microbial activity at high level. As a result, there is a decrease in
decomposition rate and respiration, resulting in a slower rate of CO2 evolution.

---

86
All residue types show the same Vend and similar slopes in this portion of the
curve., suggesting that that the second phase of the decomposition is probably
not a good element of comparison of CO2 evolution.
After 28 days of decornposition process, the remaining residues entered the
third phase of the decomposition pro&&.
At this point, the slowly available
residue components domilaled the residue substrate. Lignin, known to be
resistant to degradation, was probably the major remaining component.
The
rate and extent of lignin decomposition are affecled by temperature, availability
of nitrogen, and by constituents of the residues undergoing decay (Sarkanen et
ai., 1971). At this stage of degradation, all the readily available nutrients are
expected to vanish. Lignin is probably being decomposed by relatively slowly
growing microorganisms (Witkamp et al., 1963). Consequently, microbial
respiration is very low. As a result, CO2 evolution follows a quasi steady-state
for the rest of the decomposition. Lignin continues to disappear however.
Cotton cultivars OLP-!5690 and DP-521 5 above-ground biomass (Figures 2.1
and 2.2) showed greater cumulative COz evolution than the roots due to higher
total N, lower hemicellulose ;and lignin concentration of the above-ground
residue.
In addition, lower lignin content plus high specific surface area-to-
nass ratios for the above-ground residue provide microorganisms better access
ta available C sources (Collins et al., 1990; Jensen 1994). Cultivar HS-46
above-ground residues and roots (Figure 2.3) were not different in cumulative
CO2 evolved probably due to higher level of total concentration of N, but lower
sugar, hemicellulose and lignin contents for the above-ground biomass than the
mots. The specifïc surface area-to-mass was probably too low in aboveground
to provide microorganisms good access to available C sources.
For alll peanut cultivars (Figures 2.6, 2.7, and 2.8) above-ground residues
showed much higher cumulative COz evolved th,an the roots due to the higher
simple sugar contents available to the microorganisms, combined with lower
lignin concentration of the above-ground biomass. The insignificant difference

---

87
in sugar concentrations between Florunner, NC-7, and NC-1 1 above-ground
rosidues (Table 2.3) certainly excludes any difference in their cumulative CO2
evolved (Figure 2.9). Peanut is a legume, and the highest N level is
concentrated not in the above-ground biomass but in the root system where the
nuts are produced (Table 2.4).
fhe only sorghum cultivar, GW744BR, showing significant difference in CO2
evolution between the above-ground biomass and roots (Figure 2.12) had the
highest total N, and the lowest simple sugar and lignin concentrations in the
above-ground than the roots. For the other cultivars, Triumph-266 and Nking-
300 (Figures 2.11, and 2.13) higher available C in the form of simple sugar
concentrations in the roots probably contributed to their higher CO2 evolution
level, matching that of the above-ground residues. Sorghum roots are fibrous
and high in sugar content (Table 2.4). These results were consistent with
Leonard et al. (1963) who observed that high levels of sugars in sorghum roots
furnished the energy for the multiplication of soit microorganisms which compete
with plants for the available soil nitrogen. The data (Tables 2.3, 2.4, and 2.5)
support the differences in cumulative COt evolution among residues. These
results agreed with Collins et al. (19903 data in their study of decomposition of
winter wheat residues. They found that cumulative CO2 evolution among
residue components increased as the concentration of soluble C increased, and
CO2 production from chaff was initially more rapid than that from stems, but after
15 days, decomposition of the chaffs and stems produced CO* at the same rate.
Residue decomposition is a process in which the rate of transformation is
proportional to the qualitative amount of residue available to the
microorganisms. This qualitative amount of residue is reflected by the
concentration of the different chemical compounds and the physical nature of the
residue.
The chemical composition of the residue constitutes probably the most
important regulator of the decomposition (Knapp et al., 1983a).
In this study,
three pools were sorted out as they represented three different phases of the

---

88
CO2 evolution kinetics: i) nitrogen and readily available carbon in tha foml of
simple sugars, 2) hemicellulose, and 3) lignin. My data show that this compares
well with what Stroo et al. (1!389) have observed in predicting rate of wheat
decomposition.
Nitrogen is required by the microorganisms for the synthesis of
amino acids, nucleotides, and other compounds. These microorganisms afso
requit-e carbon source to construct all their carboin-containing biomolecules,
Hemicellulose, a non-structural carbohydrate, second only to cellulose in
quantity, represents a significant source of energy and nutrients to the
microorganisms.
Lignin is the third most abundant constituent of the plant
residues and is slow to degrade.
Residuae decomposition, as measured by cumulative CO2 evolution, cannot
be related to a single pool, but a set of all defined pools, each of them playing a
particular role. However, for legume species, the pool of N and available C in
the form of simple sugars seems to play the determinant role.
Cheshire et al.
(1988) reported that using a single pool tends to underestimate changes in the
residue decomposition with time.
In this study, the common trend in the CO2 evolution rates from the roots did
not present any real break between the second phase with decreasing of
hemicellulose availability and the steady phase with lignin availability. This was
probably due to the high <concentrations of hemicellulose and lignin present in
the roots. Most root systems store a relatively appreciable level of readiïy
available C in the fonn of sugars, but when matched with higher contents of
structural carbohydrate and lignin available to the microorganisms, the
decomposition process remains slow. The decomposition rate of roots could be
an important. information in the management strategies to prevent soil erosion by
water. Even though it has been found that root. degradation was more comptete
in undisturbed soi1 (Martin, 1989) compared to tilled soil, the results obtained
from t,his study, with air-cfried roots, would still be useful to quant@ root
decomposition.

---

89
The differences in residue decomposition between the above-ground
biomass and the roots of these cultivars used in this study is due to differences
in initial chemical and physical characteristics of the two residue components of
each given cultivar, and also in morphologie variation between cultivars (Stott,
1992). Jensen (1994) related decomposition of plant residues at different total
C:N ratios with different particle sizes. But, in the early decomposition process,
microorganisms are more likely to utilize the readily available fraction (soluble C
in the form of sugars) of the plant residues than the total C pool which includes
the more recalcitrant fraction (Stott, 1992).
In the first fourteen days, the residue mass remaining decreased quite
rapidly.
At day 15, the mass remaining started leveling off and then showed no
signifïcan,t change from day 28 until the end of the experiment. The rapidity at
which the breakdown of the residues occurred in the early phase was mainly
dependent on the initial chemical and physical nature of the residues.
For most
cases, high levels of total N and readily available C in the form of sugars were
essential to a rapid decomposition. The degradation of the leaves usually was
SO fast that even if the stems were breaking down slowly, the weight loss of the
overall above-ground still remained relatively high. Table 2.3 showed that the
peanut aboveground residues (legume) that had the fastest weight loss rate in
the early decomposition had highest concentrations of simple sugars, relatively
high N content, relatively low hemicellulose and lignin levels compared to cotton
and sorghum.
Also, peanut residues have the second highest specïfic surface
area-to-mass ratio after cotton (Table 2.6) which provides microorganisms much
better access to available C sources. Cotton above-ground residues had the
second highest level of N, relatively high concentrations of sugar, hetnicellulose,
and lignin.
For sorghum above-ground residues, a combination of low N
content, high hemicellulose level and a relatively low lignin content versus
relatively high concentrations of sugars but a lower specific surface area-to-
mass ratio of the residues made the rate of breakdown the slowest among the

---

90
trop species. These resuits were consistent with previous work of Collins
(1988) and Stroo et al. (1989).
The same pattern of COz evolution was observed in mass loss as well in this
study.
2.51. Chan#ge in the Speclfic Surface Area-ta-Mass Relationship
Specific surface area-to-mass relationship, represented by a k value, is a
specific surface area-to-mass ratio with dimension of ha kg” of residue.
In
Gregory’s 1’1982) equation, (eq. 2.7) k is specific for a given trop and
considered to be constant over time. Specific surface area-to-mass relationship
(Figures 2.35, 2.36, 2.37) ,for cotton was signifïcantly different. Cultivars DLP-
5690 and DP-5125 above-ground biomass k values were signifïcanly greater
than that of cultivar HS-46
The fïrst two cultivars were not signifïcantly different
in k value. Figures 2.38, 2.39 and 2.40 did not showed significant difference in
k values between peanut cultivars Fiorunner, NC-7 and NC-l 1.
Sorghum
cultivars Triumph-266, GW7446R and Nking-300, were not significantly different
in specific surface area-to-mass ratio (Fgures 2.41, 2.42 and 2.43). However,
there was a, significant difference between the mean k value of each species.
The initial k, value (Figure 2.44) for cotton was greater, 0.00048 ha kg-‘, than
peanut and sorghum, 0.06029 and 0.00019 ha kg-’ respectively.
In the first do-
14, days, change in specifïc surface area-to-rnass ratio was relatively rapid for
cotton and peanut , residues, but change in sorghum was quite slow.
Stott et al. (1994) found a k value of 0.000231 ha kg-’ for com from field data.
This was consistent with the range of values from this study as the three trop
species used, sorghum is the trop that is physiologically and morphologically
closest to com, and both are monocotyledons. Compared to com, sorghum bas
a lower osmotic concentration of the leaf juices, but the stalks, crown, and root
juices are higher in sorghum (Leonard et al., 1963).
In addition to its juicy stem,

---

91
sorghum leaf area is smaller than com. Therefore, sorghum residue
decomposition may be somewbat faster than com.
Consequently, a k value for
sorghum should be smaller, but close to that of com residue.
K was found to be a value specific to each trop species.
It changes within a
certain range over time during the decomposition process because it is a ratio of
specifïc surface area over mass of the decomposing residue (Eq. 2.8).
In this
study, sjgnificant differences were observed between cultivars of cotton, but not
from peanut and sorghum. However, the signifïcant difference in mean k values
between cotton, peanut and sorghum species was consistent with its specificity
to each trop (Stott, 1994).

---

0
0
8
0 m
WwiJ) 0 b
ass
0
,40-m
0
area
0
P
Q 2
Specific
0
0

---

93
0.0006 F
- * Leaf
- Stern
0 10 zo 30 40 50 60 70 80 90
Time kiavsl
Figure 2.315. Change in specific surface area-to-mass for cotton DP-5215 over
.
time.
Bars represent standard deviations at given time.

---

(halkg)

area-to-mass
1
I
P
a
1
I
I
0 ô 00
Specific surf.
0
0
s !s 0 A
ul 0
0
0
0
CO 0
-l I.
3 CD
% Y tn

---

95
0.00137
â
2
i-_-_--_-
0.0006
- - Leaf
- Stern
; 0.0005
-Aboveground
-_-A
E
9 0.0004 t
l
l
8
I
8 0.0003
e
; 0.0002
0
;5:
-0 0.0001
a
CR
0
0
10 20 30 40 50
60 70 80 90
Time (days)
Figure 2.38. Change in specifïc surface area-b-mass for peanut Florunner
over time. E?ars represent standard deviations at given time.

---

%
0.0007 r
0.0006
- * . Leaf
- Stern
-Aboveground
0.0005
0.0004
0.0003
0
AO
20
30 40 50
60 70 80 90
Time (days)
Figure 2..39. Change in specifïc surface area-to-mass for peanut NC-7 over
time.
Bars represent standard deviations at given time.

---

97
O.OOO7
.---___
0.0006
- * Leaf
- Stern
0.0005
-Aboveground
.---
0.0004
0.0003
0.0002
0.0001
0
0 10 20 30 40 50 60 70 80 90
Figure 2.40. Change in specific surface area-to-mass for peanut NC-l Y over
time.
Bars represent standard deviations at given time.

---

bo ca
ass
40-m
0
ô 0
P
area
0
ô 0 0
surf.
0
ô 0 0
pecific
‘
S
0
t
z! 3 m

---

99
0.0007
9
-.~-_~_
3 0.0006
4
u
- S t e r n
f 0.0005
-.----
E
s 0.0004
l
ii
5 0.0003
*
: 0.0002
‘g 0.0001
if
0 k-J ’ ’ * ’ ’ ’ ’ ’ ’ ’ ’ ’ ’
0
10 20 30 40
50 60 70 80 90
Time (days)
Figure 2.412. Change in specific surface area-to-mass for sorghum GW-744BR
over time. Bars represent standard deviations at given time.

---

0.0007
â
2 0.0006
-
3 0.0005
E
8 0.0004
ii
k 0.0003
.
T
0.0001
-+---
0
-L
o 10 20 30 40 50 60 70 80 90
Time (days)
Figure 2.43. Change in specific surface area-to-mass for sorghum Nking-300
over time. Bars represent standard deviations at given time.

---

(ha/kg)

area-to-mass
P 0 0 SS

I ! *’ I I i
Specific surf.
-l I.
3 CD
â
3 m
-n

---

102
2.5.2. Relationship between Mass loss and Car-bon loss
Residue decomposition cari be measured by car-bon loss or mass loss.
Carbon loss as estimated by CO2 evolution, is the most used method (Knapp et
al., 1983; Stott et al. 1986; Stroo et al., 1989; Collins et al., 1990). Measuring
decomposition via mass loss simulates changes in the fîeld and is more
important. in natural resource models that need to predict the amount of soi1
surface covered by residues at any given time.
TO relate field measurements of
residue mass IOSS to laboratory experiments, in which COz evolution is the
variable, a relationship between mass loss and COz evolution was determined
using linear regression. The mass loss-carbon loss relation was determined for
the above-ground residues and roots of three cultivars each of three species,
cotton, peanut, and sorghum (Figure 2.45). The equation of best fit was linear:
Mass loss = 0.16 + 0.58 CO2 evolution
(2.9)
where mass ioss (% de’) and COz evolution (% d-‘) rates were cafculated based
on the first 14 days of incubation.
The residue decomposition measured by COz evolution was higher than the
mass loss measurement because the simulation of field measurements of
residue mass loss involved uncontrolled fïeld conditions which, with time, did not
provide optimal conditions to the microorganisms. Stroo et al. (1989) found that
residue rnass loss was greater than the proportion of C lost as CO&, and
hypothesized that some physical fragmentation occurred during decomposition
preventing full residue recovery. For Collins (1988), the C concentration in the
wheat straw decreased slightly as decomposition progressed and some C might
be lost as gases other than C02, resulting in greater mass loss than carbon IoSS.

---

103
Y = O.-l6 +0.58X
0
r2 = 0.87
??
?
? ? ??
?
?
? ? ?
cl
1
2
3
4
5
6
7
CO2 Evolution (% d-1)
F’igure 2.45. Relationship between mass loss and COz evolution for
above-ground Ibiomass and roots of three arltivars of cotton, peanut
and sorghum in the early stage of decomposition.

---

Y =
0.35

+ 0.42X

r2
r2 = 0.96
0
1
23456789
Predictive residue Decay Rate
Figure 2.46. Relationship between mass loss and predictive decay rate using
above-ground biomass and roots of three cultivars of cotton, peanti
and sorghum.

---

104
2.5.3. Prediction of Residue Decay
This prediction of residue decay is an attempt to describe in a certain way
the contribution of different parameters to the rate of plant residue
decomposition.
The C:N ratio has been used for long time as a predictor of
decomposition, but it has been shown recently that it correlated pooriy with
decomposition rate (Stott, 1992). After it has been found that C:N ratio solely
could not suffïciently describe the rate of decomposition (Hernan et al., 1977),
lignin and lignin-to-nitrogen were also tested for a better prediction of decay rate
(Hargrove et al., 1986). Collins et al. (1990) used a relationship with total
carbohydrate, C, N and lignin and concluded that the relationship did not seem
to hold when the components were mixed before decomposition. The
relationship used to predict the plant residue decay rate included total N, simple
sugars re,adily available as fraction soluble C, hemicellulose considered as
somewhat available after the soluble fraction, and then lignin which mark the
boundary between fractions available and recalcitrant.
The predictive decay rate PD is expressed in the following equation:
PD = (N*Sugar&Hemicellulose*K) / Lignin
(2.10)
where N, (nitrogen), sugars, hemicellulose, and lignin are expressed in g kg-‘,
and k is the specific surface area-to-mass ratio (ha kg-‘).
For mass Ioss (Figures 2.46) the equation of best fit was linear in the form:
Mass loss = 0.35 + 0.42 PD
(2.11)
For COz e,volution (Figure 2.47), a linear regression fitted the equation in the
form:
CO2 evolution = 0.47 + 0.70 PD
( 2 . 1 2 )

---

105
where mass loss (% d”) and CO2 evolut,ion (% d”‘) rates were based on the first
fourteen days of incubatiori.

---

107
Y = 0.47 + 0.70x
0
.
0
l-2 = 0.95
//II
?
?
?
?
?
?
?
?
I
0
1. 2
3
4
5
6
7
8
9
Predictive residue Decay Rate
Figure 2.47. Relationship between COz evolution and predictive decay rate
using above-ground biomass and roots of three cultivars of cotton,
peanut, sorghum.

---

TQhlo
“Y,” 7 fi
L.V. Predictive ratio and Ra!e cnnstants of CO? Loss and Mass LOS~.
Crop
Cultivar
Residue
Component Predictive
Rate constant (Oh d-‘)*
Type
Ratio
Rate
coz Loss
Mass Loss
. .
.
Cotton
DLP-5690
ieaf / stem
46.7:53.3
5.45
4.2
2.9
Ï0üi
lûû
4 - i f
1.13
2.1
1.2
DP-521 5
leaf / stem
41.2158.8
4.86
3.2
2.8
root
100
0 53
0.7
0.6
H S - 4 6
leaf / stem
47.1:52.9
2.66
2.5
1.4.
I -,
root
100
2.75
2.6
1.6
Peanut
Florunner
leaf / stem
25.9:74.1
6.20
5.6
2 9
root
100
1.34
15
09
NC-7
ieaf / s!em
29 3 TO.8
.L.
7 4n
I L!
5.6
30
root
100
Y10
1.1
cl7
NC-1 1
leaf I stem
31.1:68.9
8.04
5.7
3.2
root
100
1 .Ol
0.9
0 6
Sorghum Triumph-266
leaf / stem
45.3:54.7
4.60
2.7
1.9
root
100
1.70
1.6
0.9
GW744BR
leaf I stem
38.761.3
4.02
3.4
2.3
root
100
2.40
2.4
1.4
ieai i stêm
*c) /S.ff? A
9 An
31
43.P.dU.4
3.Ltu
2.9
L. t
root
100
4.85
3.6
2.7
* The rate constant is calculated as the slope of the curve (Oh) divided by 7 days,
0
ca

---

2.6. Conclusions
The initial chemical and physical characteristics of the plant residues and
i roots impacted the rates of decomposition . The decomposition rates
l
I determined by CO2 evolution and mass loss showed differences between
! cultivars, for cotton, peanut and sorghum. Due to their leguminous nature, the
~ three peanut cultivars were decomposed rapidly, and were different in decay
~
rates among them. The degradability of peanut above-ground residue was
1 highest followed by cotton, while the sorghum above-ground decomposition fate
( was the slowest.
The plant roots did not follow the same order in degradability
( as did the plant above-ground residues. Sorghum roots were decomposed
I faster than cotton and peanut. There was significant difference between the
i decomposition rates of the cctton and peanut roots. CO2 evolution and mass
( loss methods used to determine rates of decomposition were highly correlated.
,
Changes in specific surface area-to-mass measurements showed significant
i differences between cultivars within cotton only, but there were differences
( between species as if k value was a constant specific for each trop.
It was possible to develop a prediction decay equation from the initial
i chemical and physical characteristics of the residues for the early stage of
~
decomposition.
This predictive decay equation in the early decomposition process is a
partial result that cari be used to predict decomposition rate of residue in the
I early stage. A validation of the predictive equation with decomposition rates
measured in the field Will certainly help predict the decomposition rate of any
~ plant residue over time. Once validated, this predictive decay equation Will be a
I
useful tools for land managers, conservation planners, environmental scientists
i
and even those concerned with construction sites. It also could be used as
:
parameter in a trop breeding program. Predicting residue decomposition, used
~ in a management program, cari help solve soi1 erosion problem, but also cari

---

110
he3p control accumulation of trop residues when it is viewed as a nuisance to
trop establishment and growth, or as a disposa1 problem.
Future work Will include using the predictive decay equation to develop
residue decay parameters for erosion prediction models such as RUSLE:
(Revised Universal Soit LO~S Equation), RWEQ (Revised Wind Erosion
Equation), WEPP (Water E3osion Prediction Project), and WEPS (Wind Erosion
Prediction System).

---

1 1 1
2.7. References
) Berg, B., M. Muller, and B. Wessen. 1987. Decomposition of red clover
(7tifo/&1?1 pratense) roots. Soi1 Biol. Biochem. 19589-593.
i
Bottner, P., 2. Sallih, and G. Billes. 1988. Root activity and carbon metabolism in
soils. Biology and Fertility of Soi!s 7171-78.
~ Broder, M.W., and G.H. Wagner. 1988. Microbial colonization and
decomposition of com, wheat, and soybean residues. Soil Sci. Soc Am. J.
521112-l 17.
~ Cheng, W., and D.C. Coleman. 1990. Effect of living roots on soi1 organic matter
decomposition. Soi1 Biol. Biochem. 22:781-787,
I
Cherney, J.H, J.J. Volenec, and W.E. Nyquist. 1985. Sequential fïber analysis of
forage as influenced by sample weight. Crop Sci. 251113-l 115.
~ Cheshire, M.V., J.D. Russell, and A.R. Frazer. 1988. The decomposition of plant
residues in soil. J. Sci. Food Agric. 45133-134.
I
Colliins, H.P., L.F. Elliott, R.W. Rickman, D.F. Bezdicek, and R.I. Papendick.
,
1990. Decomposition and interactions among wheat residue components.
~
Soil Sci. Soc. Am. J. 54:780-785.
Davis, J-S., and J.E. Gander. 1967. A re-evaluation of the Roe procedure for the
determination of fructose. Anal. Biochem. 19:72-79.
Elliott, L.F., H.F. Stroo, R.I. Papendick, C.L. Douglas, G.S. Campbell, and D.E.
l
Stott. 1986. Decomposition of surface managed trop residues. pp81-91.
,
1n:L.F. Elliott (ed.) STEEP Conservation concepts and accomplishments.
,
Washington State University Press. Pullman, WA

---

112
Goering, H.K., and P.J. Van Soest. 1970. Forage fiber analysis. Agriculture
Hanbook No. 379. Agricultural Research Service. USDA.
Gregory, J.M., T.R. McCarty, F. Ghidey, and EX. Alberts. 1985. Derivation and
evaluation of a residue decay equation. Am. Soc. Ag. Eng.: 98, 99, 101, 105.
Trans. ASAE.
Van Handel, E. 1968. Sucrose analysis. Anal. Esiochem. 22:280-283.
Hargrove, W.L., P.B. Ford, and Z.C. Soma. 1966. Crop residue decomposition
under controlled and field conditions. Station Bulletin Dept of Agronomy,
Univ. of Georgia, Georgia Station, GA 30223-l 797.
Herman, V.A., W.B. McG’ill, and J.F. Dormaar. l977. Effects of initial chemical
composition on decomposition of roots of three grass species. Car~. J. Soil
Sci. 5:7:205-215.
Jensen,,E.S. 1994. Mineralization-immobilization of nitrogen in soi1 amended
with Iow C:N ratio plant residues with diffenent particle sizes. Soii E3iol.
Biochem. 26519-52‘1.
K..app, E-B., L.F. Elliott, and G.S. Campbell. 1983. Microbial respiration and
growth during the decomposition of wheat straw. Soil Biol. Biochem. 15:319-
323.
L.eonard, H.W., and J.L. Martin. 1963. Cereal crops. The McMillan Company,
New York City, NY.
Martin, J.K 1989. In situ decomposition of rootderived carbon. Soil Biiol.
Biochmem. 21:973-97%4.
Sarkanen, K.V., and C.H. L.udwig, 1971. Lignins: Occurrence, formation,
structure, and reactions. Wiley-Interscience, New York City, NY.

---

113
Stott, D.E., L.F. Elliott, R.I. Papendick, and G.S. Campbell. 1986. Low water
temperature or low water potentiai effects on the microbial decomposition
of wheat residues. $00 Biol. Biochem. 18577-582.
Stott, D.E.,, H.F. Stroo, L.F. Elliott, R.I. Papendick and P.W. Hunger. 1990.
Wheat residue loss from fields under no-till management. Soil Sci. Soc. Am.
J. 54:92-98.
Stott, D.E. 1992. Mass and C losses from com and soybean residues as
associated with their chemical composition. Agron. Abstr. p.267. Paper in
preparation
Stott, D.E. 1993. Changing relationship between mass and surface area of
decomposing residues. Agronomy Abstracts p.261. Paper in preparation.
Stroo, H.F., KL. Bristow, L.F. Elliott, R.I. Papendick, and G.S. Campbell. 1989.
Predicting rates of wheat residue decomposition. Soil Sci. Soc. Am. J.
53:9 l-99.

---

114
CHAPTER 3
CROP RESIDUE DECOMPOSITION WITH CHANGE IN SOIL DEPTH
3.1. Abstract
Microorganisms play a major role in the arop residue decomposition
psocess, and it has been assumed that microbial activity is uniformed with soil
depth in a given tillage system. This study was conducted to determine
variation in residue decornposition rates related to the microbial activity with
changes in soil depth under established no-till and a moldboard plow ti’llage
system, on a silty clay loam soil at the Purdue Agronomy Research Center, West
Lafayette, IN. Soil cores were sampled at O-20 cm and then partitioned into O-l,
1-5, 5-12.5 and 12.520 cm sections constituting the different sampling soil
depths.
The peanut (Fasfiyiata vulgaris) residue used in the experiment was the
Spanish Tampsan 90 cultivar. The decomposit.ion rate was quantified by
measuringl the amount of C02-C evolved from an electrolytic respirometer
incubation system, loading .2 g of airdried residues in 100 g airdried soi1 for
each treatment. Soil depth in no-till soil, signifkantly influenced residue
decomposIition.
After 84 days, cumulative % CO* evolution from the surface soi1
(O-l cm) was high, 50%, whereas, from the lower depth soil (12.520 cm), CO&
was much lower, 22Or6. From the intermediate Idepth soil, (1-5 cm), residue
decomposition as measured by C02-C evolution was signifîcantly lower, 37%
than from the surface soiil, but significantly higher than decomposition from the
lower depth soil.
From the plowed sites, a reverse situation occurred due to

---

115
inverting residues. Residue decomposition rates from lower depth soils (512.5
cm and 12.520 cm) as measured C02-C evolution was 40% and 38%
respectiveiy, and not signifkantly different from each other, but were signifïcantly
greater than the decomposition rates, 21% and 13% CO*-C evolved from soil
obtained from the shallower depths, l-5 cm and O-1 cm, respectively. Due to
lower microbial activity, residue decomposition decreased with soil depth in no-
till situation whereas in a moldboard piow tillage system, it increased with soi1
depth.
3.2. Introduction
The amount of trop residues remaining on the soil surface and within the
top 20 cm of the soil profile are critical factors in erosion control.
A successful
trop residue management system depends upon an understanding of the factors
governing trop residue decomposition, and how much residue caver is lest from
a field site.
Tillage influences the physical environment near the soil surface, thus
affecting biological process in the soif. Soif profile differences between no-till
and conventionally tilled soi1 have been reported and cari be detected after a few
years of changing from conventional to no-till management practices (Dick,
1983). According to Doran (1980), no-till soils have more total microbial
biomass than conventionai tillage soils in the surface O-7.5 cm.
In addition,
there are increases in soil water content, organic carbon contents, and total
nitrogen levels in the no-till soils probably due to higher amounts of residue left
on the soil surface in the no-till system.
Each tillage event causes a movement
of moist soil to the surface, which then dries rapidly.
Surface residues affect soil temperature pattems and soil water content,
thus affecting biological activity in the soil (Roper, 1985). Along with soil
physical and chemical characteristics, microorganisms play a major role in the

---

1 1 6
trop residue decomposition process. Therefore, knowledge of trop residue
decompos,iiion undet a givenl tillage system, and how decomposing activities of
the microbial populations are distributed as soil depth changes would be useful
information for predictive rnodels.
The objective of this study was to determine if there is a difference with
depth in residue decomposition rates when soil is held under identical
environmental conditions.
3.3. Materials and Methods
3.i3.1. Soil and Site Description
A Drummer silty clay loam soi1 (fine-silty, mixed, mesic Typic Haplaquoll)
was used in this experiment. The sampling site was a nineteen-year tillage
cornlsoybean rotation field experiment located at the Purdue Agronomy
Research Cienter in West Lafayette, IN. The site has less than 2% slope, is
tiled at a 20-m spacing, and the soil is well structured (Table 3.2).
The plots were established in 1975 and consist of com/soybean rotation
under a variety of tillage managements. The two tillage systems sampled in this
study were: (i) fall moldboardl plowing to 20 cm, with one disking and one fïeld
cultivation to 10 cm in the spring prior to cultivation and (ii) no-till planting with
2.!%m-wide fluted coulters to tut through residues and open a slot ahead of
standard pl’anter units (Griffith et al., 1988).
The soit samples used for this experiment were taken from the no-tilf and
moldboard plow plots of com following soybean. For each treatment, four
replicate plots were sampled, The samples were taken from between rows 2
and 3 within each plot as this row was uncompaded by tieel traffic.
In each
plot, four soit cores were taken from the O-5 cm layer using rings, and four other
soil cores were also sampled from the O-20 cm layer using soil probes. The
samples were then partitioned into O-l cm, 4-5 cm, 5-12.5 ~XI, and ‘l2.520 cm

---

~
117
soit depths The soi1 samples taken with the rings were to complete the amount
( of soil needed for the experiment at depths O-l cm and l-5 cm.
The samples
( were airdried, ground to pass a Z-mm sieve, and stored until use.
I
3.32. Plant Materials
Peanut (Fastigiata vulgaris), Spanish Tampsan 90 cultivar, was grown in
5-gaIlon buckets, using a sanitized soi1 mix. The plants were grown in the
greenhouse for 125 days. On a three-week basis, the plants were treated with
specific compounds against white fiies and spidermites. After han/esting, the
aboveground biomass (stems and leaves), the below ground biomass (roots)
and the yield biomass (pods) were separated from one another. The residue
samples were washed to remove excess soil. After washing, residue samples
were dried at 40°C for 48 hr and weighed.
A subsample of plant residue was finely ground (< 0.3 mm) for chemical
analysis, using a Straub Grinding Mill (Mode1 4E, Straub CO, Philadelphia PA).
Total C, H, and N contents (Table 3.1) were determined using a dry combustion
analyzer (Mode1 CHN-600; Leco Cor-p., St. Joseph, Ml). Lignin, cellulose, and
hemicellulose contents were determined by sequential fiber analysis using thé
Goering et. al. (1970) procedure (see chapter 2 for details). Chemical analysis
were done in triplicate.
Table 3.1. Initial chemical composition of the peanut residues
Residue type
Total C Total N Cellulose
Hemicellulose L i g n i n A s h
-.-...--..----._------
p
g kg7 residue
Aboveground’
397.4
24.4
191.0
241.5
68.7
17.0
Roots
397.0
22.3
286.5
230.7
85.0
22.2
*Aboveground is the non-harvested material, primarily stems and leaves.

---

118
3.33 Decomposition Experlment
Residue decomposition rates were determined by the amount of C
evolved as COz over time. The experiment consisted of eight treatments. Four
treatments# were composed of soil from the no-till system at four depths; (O-1 cm,
l-5 cm, 512.5 cm and 12.5-20 cm), the other four were from the moldboard plow
system, at the same depths. For each treatment, 100 g soif and 2 g peanut
residue (ovendried basis) were placed in an incubation jar. The 2 g residue
consisted of ? g Stern, 0.5 g leaf and 0.5 g roc&, representing the proportion of
each residue component left in the field after harvest. The controls consisted of
soil from each treatment with no residue. The incubation jars were connected to
electrolytic respirometers (Knapp et al., 1983a). The optimal moisture content
for incubation was consiclered to be the water content at -1/3 bar water potential
as equalled to 60% water’ holding capacity, plus 300°h of the residue mass
(Myrojd et al., 1981). The moistened soil was mixed thoroughiy, the dry residue
spread ev’enly on the soil surface, soi1 to residue contact insured and then the
incubation jar was tightly sealed (Stott et al., 1986). The jars were submerged
in a water tank and insulated by putting styrofoam on. The water temperature
was maintained at 22’C I!X 1°C with a circulating water bath.
The amount of CC2 respired was captured in an alkaline trap of 5 ml 30%
K0t-L An indicator, tropaelin 0, (Sigma Chemical CO, St. Louis, MO), was
added to the KOH solution to indimte if the solution has reached a 50°r6 CO,
saturation (pH 11). TO remove the KOH, a 22-gauge needle with a Luer lock
fitting thraugh the stopper and lertgthened with a suffïcient pieca of capillary
tubing to reach the bottom of the KOH trap wili be used. Fresh KOH was
injected in the same mariner, thus the incubation chamber remained sealed
throughout the experiment (Stott et al., 1986). KOH was withdrawn after 3, 7,
14,28, 56 and 84 days of incubation. The amount of CO, evolved during the

---

119
decomposiition was measured by titration of the KOH solution using Golterman
~ (1970) potentiometric titration method.
I
3.3.4. Incubation system
The system used to incubate the soils consisted mainly of a respirometer
and an incubation jar held in a circulating water bath to maintain a constant
temperature and prevent condensation within the jars. The circulating bath
(Mode1 2095, S/N, Forma Scientific, Marietta OH) was connected to a plexiglas
water tank in which the jars were held (Stott et al., 1986). Each incubation jar
was connected to an electrolytic respirometer. At the top of each respirometer,
there was a 25 or 50-ml burette, a positive eledrode for oxygen, and a 4-cn-1 tube
for overflow. At the bottom, there is a negative eleotrode for hydrogen. Bath
electrodes were platinum. The positive electrode is connected to a 500-ml
chamber ccntaining the electrolyte solution 8% (NahSO,-
Within each incubation jar, there was a small glass cup to hold the
alkaline trapping solution. Respired CO, was absorbed in the KOH trap,
thereby reducing the total pressure in the incubation jar. This causes the
electrolyte to be drawn up into the capillary tube containing the 0, electrode.
As the electrical circuit is completed, H,O is hydrolyzed with H, being captured
in the gas burette.
(
3.35. Measurement of CO, evolution
)
The reactions involved in the KOH trapping the evolved CO, are as follows:
KOH + CO, -> HCO; + K+
~
(3.1)
HCO, + K+ + HCI ----a H,CO, + KCI
(3.2)

---

120
Each milliequivalent of KOH used to absorb evolved CO, is equivalent to 12 mg
of CO, carbon.
The formula used to calculate cumulative % C-CO, evolved is:
% C-CO, = [ K1 (11 M) * V * N * C, ]
??
(3.3)
wtlere:
K1 = CF.315 a calculated constant to convert the raw result into the desired unit
M = mass of the residue in grams
V = volume of HCI titrant in ml
N = concenitration of HCI titrant in normality
Ci = initial carbon content of the residue in percent.
3.3.6. Statistical Design
The experiment consisted in a completely randomized design with
treatment soils from two management systems, a,nd four soi1 depths (eight
treatments plus controls). The experiment was done in triplicate.
Statistical analysis of the data was t-un to determine differences among
treatments using the PC-SAS, Version 6.09 (Statjstical Analysis System 1985).
Analysis System 1985).
3.4. Results and disarssion
The mean concentrations of total C (Table 3.2) from the surface 0 to l-5
cm no-till sloil were significantly greater than that of plowed soil (P = 0.05).
However, below 5 cm, there was no significant difference in total C contents
between the two tillage systems. Within the netill system, total C contents were
not signifïcantly different frorn the surface 0 to 1-5 cm, but they were sign.ficantly
higher than those below 5 cm. No significant differenœ in total C concentration

---

121
was observed along the profile 0 to 20 cm within the moldboard plowed soii.
Total N content (Table 3.2) was significantly greater from the surface O-l cm no-
tilt than plowed soil. Below 12.5 cm, the mean concentrations of totai N of
moldboard piowed soil were significantly higher than those of no-till soil. Within
no-till system, total N contents were signifïcantly decreasing with depth soils,
whereas within the plowed soil, total N contents were increasing.
Table 3.2. Physical an# chemical characteristics of the soit samples
Depth (cm)
Tillage ‘,
Clay
Silt
Sand pH
Total C Total N
SW
W)
c4
(g kg-‘) (g kg-‘)
O-1
No-Titi
27.9
57.6
14.5
5.84 a
28.4 a’
4.0 a
M. Plow’
35.9
54.9
9.1
5.98 a
23.7 b
3.0 b
l - 5
No-Till
28.8
59.9
11.2
6.05 a
26.1 a
3.2 b
M. Plow
39.2
50.8
10.0
5.92 a
23.1 b
3.1 b
5 - 12.5
No-Till
40.3
50.1
9.7
5.01 b
23.9 b
2.9 b
M. Plow
30.2
58.4
11.3
5.50 ab
23.8 b
3.5 ab
12.5 - 20
No-Till
37.7
51.6
10.7
4.76 b
23.4 b
2.6 c
M. Plow
28.6
59.3
12.1
5.47 ab
22.4 b
6.3 ab
~
M. Plow = Moldboard Plow
??
l
‘Values within columns, followed by the same letter are not significantly different
by the Waller-Duncan’s multiple range test at P = 0.05.
Soil depth influenced significantly microbial residue decomposition in both
tillage systems. After 84 days, high microbial activity resulted in 50% CO&
evolved from the surface soil (O-l cm), as compared to 23*h C evolved from the
lowest depth soil, 12.520 cm, (Figure 3.1). The amount of the CO,-C evolved
from the intermediate depth soil, l-5 cm, was significantly (P = 0.05) lower, 36*r6,
than from the surface soil, but signifïcantly higher than the CO& evolved, 25*r6
and 23%, from the lower depth soils, 5-12.5 and 12.5 - 20 cm respectively.

---

122
In the moldboard plow system, a reverse situation occurred (Figure 3.2).
Residue decomposition rates’ did not differ from the lower depth soils, 512.5 and
12.5-20 cm, 42% and 40% C&C evolved respectively. They were, however,
significantly greater (P = 0.05) than the decomposition rates in soils from the
shallower depths, l-5 and O-l cm, measured as 27OX and 21 Oh C02-C evolved
respectively.
In the no-tilled soil, the decomposition rate in the shallow depth soils, O-l
cm and l-5 cm, did not differ significantly from rates in the lower depth
moldboard plowed soils, S-12.5 cm and 12.5-20 cm. There was also no
signifïcant difference (P = 0.05) in C evolution between the lower depth no-till
soils, 5-12.r5 un and 12.5-20 cm, and the top layer moldboard plow soils, O-l cm
and 1-5 cm.
The amount of C02-C evolved measured during the residue
decomposition process is an index of the activity of the microorganisms being
respiring.
Along the top ;!O-cm of the soil profile, residue decomposition as
determined by microbial respiration showed great differences across the no-till
and moldboard plow systems. Microbial respirat.ion in surface no-till was
significantly greater than that in plowed soit (Figures 3.1 and 3.2). At greater
depth, microbial respiraticn was much higher in moldboard plowed soil than in
no-till syst.em. These results were consistent with the observations of Barber et
al. (1977) and Doran (19e;Ob) who found that respiration rates from surface no-tilt
soils were signifkantly great,er than those from pIo& soils.
However, at a soil
depth below 50 and 75 mm, these indexes of micxobial activity were often
greater in plowed soils, reversing the trend noted in the surface 0- to- 75 mm.
In general, the presence of surface trop residues in no-till system results in
physical and chemical changes in the soil environment.
The organic matter
distribution is shifted towards the surface, the pare size distribution induces
larger macropores, water is lost more slowly due! to iow evaporation, nutrients
are translocated by plants from the subsoil to the surface during the plant life

---

123
cycle.
Consequently, optimal conditions for an increase in COn evolution are
created through a stratification of the microbial respiration at the top of the soi!
profile.
Most researchers (Campbell et al., 1976; Lal et al., 1976; and Blevins et
al., 1977) have concluded that the increased microbial activity observed in the
surface layer of reduced or no-tillage soils, is related to their greater organic
carbon C and water contents resulting from the maintenance of wop residues on
the soil surface. In the moldboard plowed soil, the trend of microbial respiration
observed was reversed (Figure 3.2). The increase in CO2 evolution due to
maximal microbial activity extended to a greater soii depth than with no-till. This
could be due primarily to the plowing action tiich inverted the residues into a
deeper depth soil. Moreover, soil air diffusion rates resulting from plowing and
cultivation accelerate the process by which soil microorganisms oxidize organic
matter which becomes considerably reduced at the surface.

---

1 2 4
‘O090 c,-
-
- O-lcm
80 -
-* ‘l-5cm
-rc!5-1 2.5 cm
70
- 012.5-20 cm
~
60 -
- l3are SoilA
_-
50 -
40 -
30 -
20 -
30 40 50 60 70 80 90
Time (days)
Figure 3.1. Cumulative CC+C evolution from different depth no-till soils
amended with peanut residue. CO2 evolved from the bare soi1 was
used to corred: the CO2 evolution from the treatments wïth residues.

---

lost

C-CO2
. \\ \\‘\\
Cumulative %
. l\\

---

1 2 6
3.5. Conclusion
Residue decomposition fates decreased with soi1 depth in a no-till
management system, whereas in a moldboard plow system, it increased with soi1
depth, when temperature and moisture are held constant. This might be due to
the fact that in no-till soil, trop residues are left at the soil surface whereas in a
moldboarcl plow system, surface residue biomas’s is incorporated into the soil
profile.
Tihis leads to an enrichment of the microbial population in the lower
levels of l.he plow layer within the moldboard plow system.
Currently, plant residue decomposition models assume a uniformity in the
activity of Imicrobial populations with depth and focuses rather on environmental
conditions.
Since this study has showed that, at least in the top 20 cm of the
soi1 profile, microbial activity is subject to changes depending upon the
management practices, the model’s assumptions that the extent of potential
microbial activity is about the same where the residues are concentrated within
the profile seem to be verified.

---

127
3.6. References
; Barber, D.A., and C.J. Standetl. 1977. Preliminary observations on the effects of
direct drilling on the microbial activity of soil, ~58-60. In: Agric. Res.
Council 1976 Annual Report, Letcombe Lab., Wantage, England.
! Blevins, R.L., G.W. Thomas, and P.L. Cornielus. 1977. Influence of no-tillage
i
and nitrogen feriilization on certain soit properties after 5 years of
continuous com. Agron. J. 69:383-386.
( Campbell, C.A., E.A Paul, and W-6. McGill. 1976. Effect of cultivation and
cropping on the amounts and forms of soil N p. 9-l 01. In: W. A. Rica [ed.].
Proc. Western Can. Nitrogen Symp., Calgary, Alberta, Canada.
’ Dick, W.A. 1984. Influence of long-term tillage and trop rotation combinations on
soil enzyme activities. Soil Sci. Soc. Am. J. 48569-574.
~ Doran, J.W. 1980. Soi1 microbial and biochemical changes associated with
i
reduced tillage. Soi1 Sci. Soc. Am. J. 44:765-771.
~ Golterman, H.L. 1970. methods for chemical analysis of fresh waters. IPI.
Handbook No. 8.. Blackwell, Oxford.
Griffith, D.R, E.J., Klavdivko, J.M., Mannering, T.D. West, and S.D. Parsons.
1988. Long-term tillage and rotation effects on com growth and yield on
)
high and low organic, p.oorly drained soils. Ag. J. 80599-605.
Knapp, E-B., L.F., Elliott, and G.S. Campbell. 1983. Microbial respiration and
growth during the decomposition of wheat straw. Soil Biol. Biochem.
15319-323.
.
Lal, R. 1976. No-tillage effects on soil properties under different crops in Nigeria.
Soi1 Sci. Soc. Am. J. 40:762-768.

---

128
Myrold, D.D., L.F. Elliott, R.I. Papendick, and G.S. Campbell. 1981. Water
potential-water content characteristics of wheat straw. Soi1 Sci. Soc. Am.
J. 45329-333.
Raper. M.M. 1985. Straw decomposition and nitrogenaze activity (&Hz
redxtion):effects of soi1 moisture and temperature. Soil Biol. Biochem.
17:6!5-7 1.
Stott, D.E.., L.F. Elliott, R.E.. Papendick, and G.S. Campbell. 1986. Low
temperature or low water potential effects on the microbial decomposition
of wheat residues. Soil Biol. and Biochem. 18577682.

---

APPENDICES

---

129
Table A. CO2 evolution from no-tilt and moldboard pbwl sails amended with peanti residue.
Sampling Date
Tillage
Soil depth Repiicate Volume HCI CO2 evdved
(cm
W-4
6)
8128193
NO-TiII
0-lcm
1
25.452
4.607
2
36.635
8.13
3
28.71
5.634
conW
10.824
No-Till
l-5 cm
1
19.603
3.925
2
18.963
3.723
3
14.01
2.163
contrd
7.141
NeTill
!î-12.5cm
1
26.149
5.185
2
20.533
3.416
3
28.919
6.058
contfoi
9.685
No-Till
12s2Ocm
1
21.86
3.965
2
24.353
4.744
3
20.845
3.639
cmltfol
9.2909
Motdboafd Plow
o-l an
1
22.087
5.056
2
27.51
6.766
3
2725
6.664
contrd
8.028
Moldboard Plow
1-5 an
1
31.179
7.152
2
37.646
9.189
3
28.323
6.252
w-bol
8.473
Moldboarct Pliow $12.5~~1
1
22.137
4.067
2
21.103
3.742
3
24.361
4.774
contrd
9.223
Mokhatd Plow 12.5-20~1
1
29.74
5.072
2
30.325
5.256
3
27.146
4.255
calt.fol
‘13.638

---

130
Table A. Continued.
Sampling Date
Tjilage
Soit depth Replicate Volume HCI CO2 evolved
W-N
(mr)
(W
9101/!33
No-Till
CI-lcm
1
111.47
18.437
2
68.532
18.863
3
101.6
18.131
wntrol
9.029
NO-731
l-scm
1
29.016
6.458
2
29.383
6.306
3
32.517
5.169
contrd
10252
NO-TN
5-12.5 un 1
32248
8.368
2
39.701
7.625
3
32.639
9.313
control
8.528
NO-Till
12s2oun
1
29.922
6.697
2
30.288
7.525
3
26.12
5.858
contrai
9.6649
Moldboard Plow
O-1 an
1
26.631
7.844
2
16.971
8.248
3
22.38
8.894
control
5.993
Moldboard Plow
l-5 cm
1
15.539
8.357
2
23252
11.436
3
16.974
7.922
wntrol
6.ôo6
MokMafdPkw s-12sun 1
43.858
8.917
2
48.578
9228
3
41.093
9.25
7.935
M o l d b o a r d Pbw 12.5-20~~1 1
32.815
8.439
2
29.983
8.241
3
26.839
6.816
cotltfol
7.87

---

131
Table A. Continued.
Sampling Date
Tillage
Soildepth Replicale Volume HCI CO2 evolved
PJ-N
0-N
(W
9;08/93
No-Tilt
o-l cm
1
116.3
31.5
2
130.25
33.81
3
132.51
33.382
contrd
19.534
No-l-8
l-5 cm
1
36.415
8.743
2
35.748
8.501
3
34.35
7.175
controil
19.487
No-l-Ill
5-12.5Q-n
1
32.303
11.872
2
34.48
112
3
26.754
11.848
contrd
7.974
NO-Tïll
42.5-2ocm
1
25.277
8.994
2
13.442
8.225
3
28.362
8.572
cxmtrd
8.259
MoldboafdPlow
o-1 cm
1
35.363
11.514
2
35.983
12.002
3
37.409
12.841
contrcl
8.176
Moldboard Plow
l-5 cm
1
43.263
11.504
2
32.929
13.188
3
38239
10.39
cxmfd
19.956
Moldboard Plonr 5-12.5cm
1
101.757
19.464
2
104.13
20.096
3
113.12
21.331
contrd
23.631
Moidboarrl Plow 12.5-2ocm
1
95.9
18.083
2
98.57
18248
3
88.987
15.527
cxmtl-d
24.483

---

132
Table A. Continued.
Sampling Dale
Tillage
Soi1 depth Replicate Volume HCI COZevdved
om
WI
(W
9J22I93
No-iii1
o-1 cm
1
88.465
36.862
2
94.14
43.692
3
92.137
42.994
cm-h-d
20.94
NO--l-N
l-5 cm
1
34.915
10.635
2
39.983
11.on
3
32.714
8.77
cQntJ-d
20.902
No-Tilt
S-12.5 cm
1
17.145
12.87
16.13
12.261
4
19.003
13.297
contd
a274
NO-Till
12.52cuTl
1
21.814
10.342
2
17.51
8.992
3
22.632
io.057
coti
11.831
MoMboadPlow
o-l cm
1
26.005
13.648
2
30.43
14.733
3
3429
16.093
contl-ol
10.198
MoIdboafdPlow
1-50-n
1
17.121
12.674
2
1262
13.777
3
14274
11.175
contml
8.455
MoldboafdPlow
5-12.5 an
1
87.143
29.692
2
95.016
31.387
3
96.121
32.772
contrd
11.377
MoldboardPiow
12s2ocfn
1
93.507
29.048
2
86.175
28218
3
84.728
25.304
contrd
12.303

---

133
Table A. Continued.
Sampling Date
Tillage
Soil depth Replicate Volume HCI CO2 evolved
W-N
0-M
(W
101201'93
No-Till
o-1 un
1
81.543
48.005
2
79.698
51.29
3
85.312
44.854
contfol
92705
No-Till
l-5 cm
1
67.18
18.621
2
56.076
17.836
3
62.668
18.651
cxr&ol
8.006
NO-l-61
s-MJi5NDIX
21.183
14.727
2
14.176
34.871
3
23.298
15.44
wn:rol
7.42
NO-7-d
12s2Ocnl
1
28.31
13.005
2
22205
10.831
3
30.167
11.623
conlfol
8.584
Moldboard Plow
o-l cm
1
13299
9.925
2
16.321
15.93
3
20278
17.623
conLrol
7.456
Moldboarrj Plow
l-SUIl
1
13.626
13.538
2
16.31
15.002
3
1525
12.258
wntrd
7.231
MoidboardPlow 5-12.5~11
1
13.951
30.494
2
16.U9
32.526
3
la.322
34.104
control
8.012
Moldboard Ww 12.5-20~~1
1
59.783
35.891
2
62.742
35.463
3
64.044
32.725
wnlrul
9.076

---

134
Table A. Continued.
Sampling Date
Tillage
Soildepth
Repli&e Volume HCI C02evolved
(4
WI
WI
11117’193
No-Tilt
o-1 cm
1
118.98
45.678
2
113.1
51.346
3
116.41
54.506
conlrd
10.5261
No-Till
l-fia-n
1
136.69
25.361
2
13329
18.554
3
124.69
25.385 ,
contrd
12.9856
No-l-il1
s-12.5 cfn
1
114.08
21.998
2
113.74
23.856
3
ua.03
28.4a9
mnll-ol
12.5632
No-Titi
12-s-2ocm
1
10272
24.951
2
92.911
16.885
3
105.71
25.304
contfol
12.8847
Moldboad Plow
o-l cm
1
105.76
i a.933
2
127.39
15.884
3
115.35
17.083
Gontfol
11.4571
MoldboardPlow
l-5 cm
1
146.73
la.447
2
159.03
20.118
3
14218
24.825
control
12.0564
MobdtaardPlow 5-12.5 an
1
155.3
38.4552
2
14923
40.584
3
122.63
35.59
contrd
10.5238
MoldboardPlow 12s2oun
1
138.16
34.623
2
133.10
31.412
3
14524
35.959
amtrd
92351

---

145
Table 8. CO2 evoltiion from soit amended with cotton ,residues.
Sampking Date
Cultivar
Residue
Replicate
Volume HCI CO2 evohred
(mr)
w
01/07/Q4
OLP-56!30
Aboveground
1
36.802
8.816
2
36.147
8.609
3
39.838
16.072
wntrol
8.814
Root
1
35.465
8.998
2
37.274
9.585
3
z-Q.617
7.163
contrai
8.906
DP-5215
Abovegnx~r~I
1
42.898
11.081
2
u.31
11.526
3
36.44
9.047
contfol
7.7ia
Roo!
1
11.208
1.W
2
19.712
4.343
3
13.954
2.529
0Wrd
5.924
HS-46
Above~round
1
30.417
8.04
2
32.489
8.692
3
34.084
9.195
control
4.892
1
31.916
7.92
2
30.1?1
7.351
3
32.638
8.147
contrd
6.771
SampJing Date
Cultivar
Residue
Replicate
Voluma HCI CO2 evoked
ON
WI
Ol/li'1/94
DLP-5690
Aboveground
1
47.774
13.878
2
42.452
12.199
3
42.117
12.091
conti
3.722
1
22.112
5.649
2
23.527
6.091
3
31.598
8.637
contml
4.177
DP-5215
&mground
1
37213
9.992
2
3.3353
8.934
3
41.594
11.373
contfol
5.489
1
14.836
2.75
2
10.527
3.282
3
14.19
2.548
wntrol
6.105
HS-46
Aboveground
1
35.986
9.806
2
41.309
11.483
3
37.654
10.331
contrd
4.85(
1
43.354
11.65
2
33.4a6
a.548:
3
43.609
11.737
coti
6.347

---

136
Table EL Conlinued
Sampling Date
Cultivar
Residue
Replicale Volume HCI CO2 evolved
(mr)
fi)
01118l94
OLP-5690 Aboveground 1
45.272
12.382
2
42.227
Il .423
3
45.224
9.2174
control
5.862
RO0t
1
28.654
6.411
2
31275
7.174
3.
26.557
5.688
contrd
8.499
r
OP-5215
Aboveground
1
36.638
8.675
2
37.826
9.05
c
3
42.816
10.622
.>;
L
cmtrol
9.094
ROOt
1
21.623
3.367
2
26.762
5.005
3
32.816
6.912
a.
cuntfol
10.87
US-46
Abweground
1
34.074
7.%l
2
43.664
11.051
3
39.345
15.921
contrd
6.799
RCXd
1
39.803
8.892
2
45.515
10.691
3
38.588
5.359
contrd
11.573
Sampling Date
Cuttivar
R&ue
Repli&e V o l u m e HCI C O 2 evoived
(mr)
WI
:
02/01194
OLP-5690
Aboveqound
1
54.596
14.643
2
39.725
9.959
3
46.41
12.065
cmtrd
8.106
R0Ot
1
50.65
13.097
2
41.599
10.163
3
41.159
10.044
contml
927
OP-5215
Aboveground
1
28.301
5.68
2
36.699
8.525
3
352Q5
8.063
contrd
9.633
ROOt
1
29.14
5.827
2
38.976
8.925
3
33.667
7253
contrd
10.641
HSd6
Abovegmund
1
36.741
4.981
2
35.502
7.091
3
46.061
10.417
contrd
12.99
ROOt
1
38.138
7.821
2
39.013
8.098
3
27.758
4.551
corltd
13.3OQ

---

137
TaMe 8. Conlinued
Sampling Date
Cultivar
Residue
Repticate Volume HCI CO2 evolved
(mr)
tW
OYOlf94
D L P - 5 6 9 0 Abweground 1
42.405
10.299
2
37.Q42
8.893
3
34.43
7.787
ContJ-ol
9.709
Root
1
43.19
10.173
2
51.081
12.659
3
40.2%
9.262
controt
10.893
DP-5215
Atxwgnx~nd
1
30.515
6.298
2
29.354
5.933
3
30.208
6227
contlol
10.519
Rot
1
30.137
5.897
2
32.763
6.724
3
35.492
7.584
wntrol
11.414
HS-46
Aboveground
1
20
1.597
2
24.378
2.976
3
29.349
7.691
ContKA
14.93
Root
1
42.395
9.233
2
32.1(8
6.006
3
41.523
8.959
13.cm
Sampling IDate
Cuttivar
Residue
Repkate Volume HCI CO2 evolvc~
0-M
cw
03Ev94
‘ D L P - 5 6 9 0 Aboveground 1
2Q.388
4.455
2
22.722
5.19
3
25.%6
6.079
control
6244
Root
1
2828
6SKM
2
34.041
7.819
3
26.153
5.33
wntrot
9218
DP-5215
Aboveground
1
21.312
4.023
2
22.553
4.414
3
25.714
8.OQQ
8%
Root
1
26.377
4.106
2
34.433
6.724
3
28.074
1.571
wntrol
13.085
HS46
Abovegfound
1
23.304
3.802
2
23.618
3.901
3
29.506
5.784
cow
11233
Root
1
29.388
5.185
2
35cn32
6.981
3
39.702
8.434
12.927

---

138
TaMe C. CO2 evofufion from amended with peanut residues.
Sampling D a t e Cultivar
Residue
Repkate
volume HC1
C02evoIved
O-n9
PJ)
01107/94
Flotunner
Abovegrotmd
1
57.68a
16.7U
2
54.927
15.874
3
63.257
la.496
contrd
4.531
Rod
1
23.105
6.331
2
21229
5.74
3
19.802
5.291
contrd
3.004
NC-7
Abovegrd
1
55.w
21.769
2
53.194
14.791
3
59.837
18.884
controt
6236
Root
1
M.321
4.413
2
26.458
6.348
3
23.389
5.379
contrd
6.31
NC-11
Abovegrd
1
64.357
18.303
2
60.58
17.113
3
50.836
14.045
controt
6.25
RoCIt
1
20.765
4.04a4
2
18.087
3204
3
19.426
3.626
cmtrol
7.912
Sampling D a t e Cuttivar
Residue
Replicote
Volume HCI
C02evolved
WI
(SC)
01/11194
Florunner
Abovegrd
1
72.47
21.416
2
72.078
21292
3
81.329
242CS
control
4.482
Root
1
19.536
5.283
2
18.76
5.039
3
17.021
4.491
control
2.762
NC-7
Abovegrd
1
77.439
22.458
2
78.409
22.763
3
69.781
20.046
conttvi
6.142
RWt
1
19.818
4.078
2
12.05
1.631
3
15.934
2.854
contrd
6.871
NC-1 1
Abvegtd
1
78.608
23.048
2
77x4
22840
3
62-152
25.74
control
5.438
RoOt
1
16.526
3.676
2
11.794
1.519
3
13.103
2.597
contrd
4lss

---

139
TaMe C. Continued
Sampling Date Cultivar
Residue
Replicate
Volume HCI CO2 evolved
WI
WI
OU18194
Florunner
Abovegd
1
65.556
17.659
2
69.144
18.789
3
67.386
15.085 .
umlrol
9.494
1
23.601
3.521
2
34.305
6.893
3
26.134
4.319 .
control
12.422
NC-7
Abovegrd
1
68.505
14.199
2
63.581
12.648
3
70.333
14.775
CmltfQl
23.428
Root
1
19.943
3.282
:2
13.561
1.272
:3
16.752
2.277
wrllrol
9.522
NC-l 1
AbWegid
'1
3529
14.854
2
37.517
8.84
3
26.597
5.501
ContfQi
9.133
Rloot
1
13.661
1.602
2
12.61
1.208
3
13.551
1.504
contml
8.774
Sampling Date Cultivar
Residue
Replicate
Volume HU CO2 evotved
ON
lW
02/01/94
Florunner
Abovegfd
1
48.081
11.851
2
57.352
14.771
3
58.875
8.951
control
10.457
Root
1
18.8
1.497
21
20.1
1.907
3
M.867
2.1489
control
14.045
NC-7
Abovegrd
1
36.688
9.285
2
48.692
12.u2
3
30.816
7.441
7.191
ROOt
1
22.742
4.16
2
16.893
2.317
3
19.816
3.239
control
9.535
NC-1 1
Abovegrd
1
31.055
6.589
2
36.909
7.122
3
31.026
15.336
cutl1rol
10.137
Root
1
14297
3.072
2
12.939
2.645
3
13.618
2.859
wntrol
4.541

---

140
Table C. Continued
Samplirq Date Cultivar
Residue
Replicate Volume HCI
C02evolved
(mr)
w
03lOlIQ4
Flotunner
Abovegtd
1
32.579
6.422
2
32.468
6.387
3
35.011
7.188
controt
12.189
ROOt
1
20.668
0.67
2
29.078
3.319
3
30.363
3.723 .
COl-JtrOJ
18.541
NC-7
Abovegrd
1
34.804
5.342
2
32.648
4.725
3
36.702
5.94
'
control
17.643
Root
1
22.385
3.696
2
20.284
3.035
3
21.298
3.354
control
10.649
NC-1 1
Abovegtd
1
38.067
8.797
2
34.764
7.757
3
36.099
8.171
control
10.157
ROOt
1
21.375
2.778
2
27.712
4.774
3
24.562
3.782
control
12.554
Sampling Date Cuttivar
Residue
Repkate
Vdume Ha
C02evofved
(ml)
eC>
Abovegrd
1
18263
2.159
2
10.178
1 . 4 9 5
3
31.409
6.293
contfol
11.429
Root
1
17.492
1.343
2
17.023
1.1954
3
15.984
0.668
comol
13.228
NC-7
Abovegrd
1
23.112
3.853
2
21.312
3.286
3
17.329
2.031
cotltrol
10.879
Root
1
14.688
1.486
2
12.55
0.81
3
13.108
0.989
control
9.978
NC-11
Abovegrd
1
17.325
2.583
2
23.369
4.487
3
18.674
3.006
control
9.123
ROOt
1
22.221
4.162
2
15.659
2.OQ5
3
16.918
3.131
cmtrol
9.005

---

141
Table 0. CO2 evolution from soi1 amended with sorghum residues.
Sampling Date Cultivar
Residue
Repkate
Volume HCI
COZevolved
0-N
(W
01/07/94
Triumph-266 Aboveground
1
30.163
7.194
2
30.702
7.364
3
39.189
10.037
7.322
ROOt
1
26.159
6.229
2
28.422
6.942
3
26.517
6.342
contI-ol
6.362.
GW-744BR Aboveground
1
43.466
11.011
2
46.74
12.042
3
47.942
15.571
a.509
Root
1
45.661
9.231
2
44.567
8.817
3
42.852
a.277
ContrQl
18.575
NKing-300 <Above~rtx~nd
1
37.762
9.Q62
2
42.892
11.578
3
37.676
16.235
6.135
ROOt
1
46.61
12.973
2
47.412
12.596
3
52.314
14.1407
7.422
Sampling Date CuHivar
Residue
Repkate
Volume Ha
C02evolved
WI
t-W
01/11/94*
Triumph-266 Aboveground 1
42.291
ll.oBQ
2
41.432
4.518
3
43.849
11.53
tXWtd
7.088
Root
1
18.632
4.228
2
19.263
4.427
3
23.385
5.725
Noa
GW-744BR Abweground
1
71.661
21.075
2
70.148
20.536
3
68.987
10.714
4.953
RO0t
1
23.372
5.703
2
23.845
12.152
3
25.322
6.317
5.266
NK-300 Aboveground
1
32.136
a.705
2
37.58
10.42
3
4Q.52
14.496
4.499
Root
1
37.572
9.97
2
45.316
12.41
3
41.444
11.19
5.919

---

132
Table 0. Continued
Sampling D a t e Cullivar
Residue
Replicate Volume HCI
C02evolved
WI
Vd
01/18/94
Triumph-268 Atnweground
1
22.29
4.137
2
24.511
4.836
3
22.933
10.63
control
9.155
Rwt
1
27.526
4.901
2
30.892
9.112
3
37.551
8.059
contfol
11.965
GW-744BR Aboveground
1
5ô.014
13.856
2
45.871
10.661
3
53.869
19.48
contml
12.025
Root
1
59.883
17.142
2
60.284
17.268
3
84.588
18.624
controt
5.461
NK-300
Aboveground
1
45.046
10.839
2
42.693
10.097
3
41.149
a.461
contrd
10.637
Root
1
78.258
15.478
2
84.137
23.63
3
78.099
5.978
contJd
9.118
Sampling Date
Cuitivar
Re&lue
Replicate Volume HC1
C02evdved
(mr)
CW
02/01/94
Triumph-M Aboveground
1
32.78
8.%7
2
36.843
3.046
3
37.233
9.469
7.1703
ROOt
1
34.93
420Q
2
46.195
10.907
3
30.047
5.821
cmtrol
11.567
GW-744BR Aboveground
1
42.528
9.598
2
39.038
a.499
3
37.642
14.359
controt
12.0561
Root
1
51.488
12.94
2
45.546
11.076
3
44.188
10.647
contrd
10.388
NK-300
Aboveground
1
45.148
lO.sf33
2
43.64
10.088
3
42.536
9.741
contrd
11.614
ROQt
1
31.526
8.726
2
32.775
7.119
3
31.061
3.429
contrd
10.173

---

143
Table 0. Conlinued
SampIing Oak Cultivar
Residue
Repiicate Volume HCI
CO2 8VOhd
0-N
i-3
woll94
Triumph-266 Aboveground
1
81.446
10.811
2
51 s82
13.7M
3
57.166
9.169
contful
8.0766
Rwt
1
24.567
2.979
2
34.39
6.074
3
35.362
9.5303
control
15.107
GW-744BR Abovegmund
1
31.492
4.947
2
38.695
10.366
3
43.645
8.775
ConlrQl
15.766
ROOt
1
40.399
10.011
2
37.0
9.159
3
33.779
7.955
ci2ntml
8.5226
N K - 3 0 0 Ahveground
1
45.086
9.9
2
45.699
10.1
3
38.03
7.69
cantrol
13.612
ROd
1
30.529
5.694
2
40.847
8.944
3
42.851
9.575
controt
12.452
Sampling D a t e Cuttivar
R&ue
Replicate Volurne HU
002 8VdVed
0-N
QQ
03rm94
Triumph-265 Aboveground
1
23.184
4.921
2
29.321
6.854
3
30.275
7.155
c#altrol
7.5591
ROd
1
28.514
5.856
2
33.359
7.382
3
28.454
5.837
control
9.9225
GW744BR Aboveground
1
22.685
1.562
2
37.475
8.178
3
32.749
4.69
cQntrol
17.86
Root
1
29.653
8.521
2
26.256
5.451
3
16.657
2.427957
control
8.9492
NK-300 Aboveground
1
40.508
8.451
2
25.596
3.754
3
38.26
13.098
controt
i 3.678
RWt
1
25.317
3.836
2
25.528
3.902
3
32.813
6.197
cxmrd
13.13a

---

144
TableE, Masslossofcotton residue.
Sampling Date Cultivar
Res&te Replicale Initial weight Final weight m
mass 10s
02)
(a)
(s)
es)
01/07/94
OLP-5690 Leaves
1
0.9
0.62
0.17 16.191
Leaves
2
0.9
0.64
0.17 15.471
Leaves
3
0.9
0.63
0.17 15.831
Stems
1
1.1
0.95
0.06
7.947
Stems
2
1.1
0.99
0.06
6.433
Stems
3
1.1
0.91
0.06
9.461
Roots
1
2
1.8
0.U
4.616
Roots
2
2
1.88
0.U
4.039
Roots
3
2
1.75
0.u
4.977
DP-5215 Leaves
1
0.9
0.83
0.16 4.464
Leaves
2
0.9
0.63
0.16 13.954
Leaves
3
0.9
0.65
0.16 13.305
Stems
1
1.1
0.98
0.02
6.137
Slems
2
1.1
0.95
0.02
7.452
Stems
3
1.1
0.98
0.02
6.137
RQ0t.S
1
2
1.82
0.1 22
Roots
2
2
1.91
0.1
1.492
RWts
3
2
1.85
0.1 1.964
t-E-46 Leaves
1
0.9
0.74
0.11 10.806
Leaves
2
0.9
0.65
0.11
14.5(2
Leaves
3
0.9
0.6
0.11 16.582
Stems
1
1.1
0.8
0.16 16.757
Sterns
2
1.1
0.92
0.16 12385
Stems
3
1.1
0.94
0.16 11.857
RO0ts
1
2
1.72
0.1
2.406
Roots
2
2
1.71
0.1
2.47
Roots
3
2
1.M
0.1
2.786
Samphg Date Cultivar
Residue Repkate Initial weight Final weight Ash
mass loss
(9)
Is)
(s)
t-4
Ol/ll/Q4
OLP-5690 Leaves
1
0.9
0.66
0.17 14.752
Leaves
2
0.9
0.6
0.17 16.911
baves
3
0.9
0.61
0.17 16.551
Stems
1
1.1
0.06
0.06 7.568
Stems
2
1.1
0.93
0.06
8.704
Slems
3
1.1
0.91
0.06
9.481
Roots
1
2
1.7
0.44
5.337
RO0t.s
2
2
1.83
0.44 4.4
ROds
3
2
1.75
0.u
4.977
DP-5215 Leaves
1
0.9
0.86
0.16 12.981
Leaves
2
0.9
0.56
0.16 16.228
Leaves
3
0.9
0.63
0.16 13.954
Stems
1
1.1
0.97
0.02
6.575
Stems
2
1.1
0.98
0.02
6.137
Stems
3
1.1
0.96
0.02
7.014
Roots
1
2
1.71
0.1 3.@34
ROOb
2
2
1.68
0.1 3.3
Roots
3
2
1.74
0.1
2.628

---

115
Table E. ,Continued
l-E-46
Leaves
1
0.9
0.63
0.11
15.35
Leaves
2
0.9
0.61
0.11
16.1 58
Leaves
3
0.9
0.6
0.11
1 EL562
Sterns
1
1.1
0.78
0.16
17.485
Stems
2
1.1
0.84
0.16
15.3
Stems
3
1.1
0.89
0.16
13.478
Rools
1
2
1.7
0.1
2.533
Roots
2
2
1.56
0.1
3.42
Roots
3
2
1.56
0.1
3.42
Sampling Date Cultivar
Residue Replicate Initial weight Finalweight Ash
marv ioss
(SI
63)
(SI
CW
01118/04
OLP-5690 Leaves
1
0.9
0.59
0.17 17271
Leaves
2
0.9
0.63
0.17 15.631
Leaves
3
0.9
0.58
0.17
1'7.63
Stenns
1
1.1
0.93
0.06
8..704
Stenns
2
1.1
0.89
0.06 101.218
Stems
3
1.1
0.94
0.08
8.325
ROOLS
1
2
1.79
0.u 4.666
Roots
2
2
1.73
0.44
5.121
Ftoots
3
2
1.68
0.u
5.481
DP-5215 Leaves
1
0.9
0.61
0.16 14.603
L#eaves
2
0.9
0.62
0.16 14279
Lieaves
3
0.9
0.52
0.18 17.524
Stems
1
1.1
0.92
0.02
8.767
Stems
2
1.1
0.93
0.02
8.329
Stems
3
1.1
0.91
0.02 9.2CM
ROC%S
1
2
1.7
0.1
3.142
R0d.S
2
2
1.89
0.1
1.85
F!ooXs
3
2
1.7
0.1
3.142
HS-46 Leaves
1
0.9
0.58
0.11
17.37
Leaves
2
0.9
0.6
0.11 16.932
Laaves
3
0.9
0.5
0.11 20.601
Stems
1
1.1
0.92
0.16 12.385
Stems
2
1.1
0.94
0.16 11.657
Stems
3
1.1
0.95
0.16 11.292
Roots
1
2
1.53
0.1
3.61
RC&
2
2
1.47
0.1
3.99
RC&
3
2
1.6
0.1
3.166
Sampling Date Cuttivar
Residue Replimte Initialweight Finalweight Ash mass bss
(SI
(SI
(SI
(%)
02/01/94
OLP-5690 Leaves
1
0.9
0.47
0.17
21.588
Leaves
2
0.9
OS
0.17
16.71
Laaves
3
0.9
O.Sl
0.17
20.149
Stems
1
1.1
0.67
0.06
18.543
Stems
2
1.1
0.81
0.08
131245
Slems
3
1.1
0.78
0.06
14.381
FbOtS
1
2
1.59
0.44
6.131
Rcds
2
2
1.56
0.u
8.347
Ro~ts
3
2
1.6
0.u
6.059

---

146
Table E. Continued
DP-5215 Leaves
1
0.9
0.5
0.10 18.173
Leaves
2
0.9
0.53
0.16
17.2
Leaves
3
0.9
0.52
0.16 17.524
Stems
1
1.1
0.91
0.02
9.206
Stems
2
1.1
0.85
0.02 11.836
Stems
3
1.1
0.93
0.02
8.329
Roots
1
2
1.37
0.1
5.735
Roots
2
2
1.59
0.1
4.007
Roots
3
2
1.53
0.1
4.478
H S - 4 6 L e a v e s
1
0.9
0.51
0.11 20.196
Leaves
2
0.9
0.53
0.11 19.391
Leaves
3
0.9
0.46
0.11 22.217
Stems
1
1.1
0.89
0.10 13.478
Stems
2
1.1
0.88
0.16 13.642
Slems
3
1.1
0.89
0.18 13.478
Roots
1
2
1.39
0.1
4.496
RO0t.s
2
2
1.43
0.1
4.243
ROOis
3
2
1.37
0.1 4.623
Sampling Date Cultivar
Residue Repiicate Initiai weight Final weight Ash
mass bss
(9)
09)
(a)
CW
OYOm4
DLP-5690 Leaves
1
0.9
0.41
0.17
8.203
Leaves
2
0.9
0.51
0.17
6.98
Leaves
3
0.9
0.49
0.17
7.209
Stems
1
1.1
0.65
0.06
5.647
Slems
2
1.1
0.55
0.06
6.993
Stems
3
1.1
0.8
0.06
4.127
ROOts
1
2
1.43
0.44
5.505
ROOts
2
2
126
0.44
6.431
ROOts
3
2
1.42
0.44
6.431
5.559
DP-5215 Leaves
1
0.9
0.47
0.16
7.402
Leaves
2
0.9
0.49
0.16
7.151
Leaves
3
0.9
0.42
0.16
8.03
Stems
1
1.1
0.59
0.02
6.293
Stems
2
1.1
0.67
0.02
5.343
Slems
3
1.1
0.71
0.02
4.866
ROOts
1
2
1.36
0.1
4.56
ROOts
2
2
1.33
0.1
4.676
Rwis
3
2
1.35
0.1
4.75
HS-46 Leaves
1
0.9
0.53
0.11
6.32
Leaves
2
0.9
0.49
0.11
6.647
Leaves
3
0.9
0.48
0.11
6.979
Stems
1
1.1
0.84
0.18
4.433
Stems
2
1.1
0.87
0.16
4.116
Stems
3
1.1
0.81
0.16
4.75
ROOl
1
2
1.32
0.1
4.94
R0Ots
2
2
125
0.1
5.363
Roots
3
2
1.35
0.1
4.75

---

147
TaMe E. Conlinued
Sampling Date Cuftivar
Residue Repkate Initial weight Final weight Ash
mass loss
(SI
62)
(9)
CW
03/29/94
DLP-5690 Leaves
1
0.9
0.54
0.17
6.!587
Leaves
2
0.9
0.54
0.17
8.!57
Leaves
3
0.9
0.67
0.17
4.1371
stems
1
1.1
0.75
0.06
4.7
Stems
2
1.1
0.8
0.06
4.'127
Stems
3
1.1
0.74
0.06
4.615
Roots
1
2
1.62
0.44
4.469
R&.s
2'
2
1 2 8
0.44
6.322
Rcnts
3
2
1 2 8
0.u
6.322
DP-521 5 Leaves
1
0.9
0.78
0.16
3.513
Leaves
2
0.9
0.47
0.16
7.402
Leaves
3
0.9
0.46
0.16
7.528
Stems
1
1.1
0.46
0.02
7.6
Slams
2
1.1
0.42
0.02
8.312
Skms
3
1.1
0.38
0.02
8.787
Roots
1
2
1.06
0.1
BS188
Roots
2
2
1.12
0.1
6.2!06
Ro~ts
3
2
1.14
0.1
6.08
M-46 Leaves
1
0.9
0.5
0.11
6.715
Leaves
2
0.9
0.64
0.11
4.872
Leaves
3
0.9
0.66
0.11
4.608
Stems
1
1.1
0.54
0.16
7.6
Stetns
2
1.1
0.63
0.16
6.tfi
Stems
3
1.1
0.56
0.18
7.388
Roots
1
2
12
0.1
5.7
R O M S
2
2
1.14
0.1
6.08
RoMs
3
2
1.73
0.1
2.343

---

148
Table F. Mass 10% of peanut residues.
Sampling Date Cultivar Residue Repkate Initial weight Final weight Ash
massloss
&Il
(SI
Cs)
QV
01/07/94
Fiorunner Leaves
0.57
0.35
0.1
11.605
Leaves
0.57
0.41
0.1
9.429
Leaves
0.57
0.37
0.1
10.88
Stems
1.43
1.33
0.07
7.876
Stems
1.43
1.35
0.07
6.95
Stems
1.43
1.29
0.07
9.73
RoOtS
2
1.68
023
1.585
RootS
2
1.6
023
1.751
Roots
2
1.58
023
1.807’
NC-7 Leaves
0.57
0.45
0.09
8.845
Leaves
0.57
0.4
0.09
10.0S1
Leaves
0.57
0.39
0.09
11.372
Stems
1.43
1.35
0.07
6.75
Stems
1.43
1.33
0.07
7.65
Stems
1.43
1.36
0.07
6.3 .
Roots
2
1.35
024
1.867
Rods
2
1.29
024
1.993
Roots
2
1.37
024
1.825
NC-I 1 Leaves
0.57
0.37
0.16
14.498
Leaves
0.57
0.41
0.18
12.887
Leaves
0.57
0.47
0.16
10.471
Stems
1.43
1.3
0.04
7.528
Stems
1.43
1.31
0.04
7.085
Slems
1.43
1.28
0.04
8.414
Roots
2
1.21
0.44
2.772
Roots
2
1.19
0.44
2.817
R o o t s
2
1.22
0.u
2.75
Sampling IDate Cultivar Residue Replicate Initial weight Final weight Ash
mass loss
(9)
(SI
&Il
m
Ol/l lJ94
Flotunner Leaves
1
0.57
0.43
0.1
8.704
Leaves
2
0.57
0.4
0.1
9.792
Leaves
3
0.57
0.45
0.1
7.979
Stems
1
1.43
1.38
0.07 5.56
stems
2
1.43
1.4
0.07 4.633
Slems
3
1.43
1.36
0.07
6.487
Ro4AS
1
2
1.48
023 2.085
RCX3tS
2
2
1.48
023
2.085
Roots
3
2
1.5
023
2.029
NC7 Leaves
1
0.57
0.31
0.09
14.742
Leaves
2
0.57
0.35
0.09
13.057
Leaves
3
0.57
0.41
0.09
1023
Sterns
1
1.43
1.3
0.07
9
Stems
2
1.43
1.29
0.07 9.45
Stefns
3
1.43
12
0.07
13.5
Roots
1
2
122
024
2.14
Roots
2
2
1.19
0 2 4 2.203
RoOtS
3
2
1 2 3
024
2.119

---

149
Table F. Mass loss ofpeanut residues.
NC-11
Leaves
1
0.57
0.31
0.16
113.915
Leaves
2
0.57
0.35
0.16
1!5.304
Leaves
3
0.57
0.4
0.16
13.29
Stems
1
1.43
1.28
0.04
0.414
Stems
2
1.43
1.25
0.04
9.742
:Stems
3
1.43
1.29
0.04
7.971
Iaots
1
2
1.12
0.44
2.975
Ro&
2
2
1.16
0.u
2.885
Ro~ts
3
2
1.02
0.44
3.2
Sampling Date Cultivar Residue Replicate lnitialweight Final weight
messloss
(a)
(SI
(9)
CW
Oll18M
Florunner Leaves
1
0.57
0.33
0.1
12.331
Leawes
2
0.57
029
0.1
13.782
L.eaves
3
0.57
0.37
0.1
10.88
Stems
1
1.43
1.35
0.07
0.95
Stems
2
1.43
1.34
0.07
7.413
Stems
3
1.43
1.32
0.07
8.34
Rocas
1
2
1.41
0.23
2.279
~Ro~ts
2
2
1.45
023
2.168
IRoots
3
2
1.38
023
2.363
NC-7 Leaves
1
0.57
0.28
0.09
if).006
Leaves
2
0.57
0.28
0.09
18.008
Leaves
3
0.57
0.32
0.09
14.321
!Slems
1
1.43
1.26
0.07
110.8
Stems
2
1.43
122
0.07
112.6
Stems
3
1.43
121
0.07
13.05
Roots
1
2
0.99
0.24
2.622
Roots
2
2
1.1
0.24
2.391
1aots
3
2
0.95
0.24
2.708
NC-11 Leawes
1
0.57
0.36
0.16
14.901
Leawes
2
0.57
0.34
0.16
l!i.706
Leawes
3
0.57
0.33
0.18
1f1.109
Sterns
1
1.43
126
0.04
9.3
Stems
2
1.43
1.22
0.04
111.071
Stems
3
1.43
125
0.04
9.742
Roots
1
2
0.95
0.14
3.358
ROMS
2
2
0.98
0.u
329
RoOts
3
2
1.02
0.u
3.2
Sampling Date Cultivar Residue Replicate Initialweight Finalweight
massloss
(9)
(SI
(SI
W)
02/01/94
Florunner ieaves
1
0.57
0.42
0.1
9.067
Leawes
2
0.57
0.48
0.1
6.891
Leawes
3
0.57
0.47
0.1
7253
Stefns
1
1.43
1.3
0.07
9.266
Stern
2
1.43
1.31
0.07
a.803
slems
3
1.43
1.35
0.07
6.95
Roots
1
2
123
0.23
2.78
Roots
2
2
124
023
2.752
Roots
3
2
12
023 2.884

---

TaMe F . Continued
NC-7 Leaves
1
0.57
0.21
0.09
18.954
Leaves
2
0.57
0.3
0.09
15.163
Leaves
3
0.57
029
0.09
15.584
Stems
1
1.43
1.37
0.07
5.85
Slems
2
1.43
1.39
0.07
4.95
Stems
3
1.43
1.37
0.07
5.85
RW!S
1
2
0.85
0.24
2.916
Roofs
2
2
0.96
0.24
2.665
Rwts
3
2
0.91
0.24
2.79
N C - l 1 L e a v e s
1
0.57
0.51
0.16
8.66
Leaves
2
0.57
0.49
0.16
9.665
Leaves
3
0.57
0.49
0.16
9.665
Slems
1
1.43
1.37
0.04
4.428
Stems
2
1.43
1.39
0.04
3.542
S!ens
3
1.43
1.38
0.04
3.985
Roots
1
2
1.04
0.U
3.155
Roots
2
2
1.12
0.u
2.975
ROOb
3
2
1.09
0.U
3.043
Sampling Date Cuttivar Residue Replicate Initial weight Final weight
mass bss
(SI
@)
@)
PJ)
03lOlr34
Florunner Leaves
1
0.57
0.14
0.1
19.222
Leaves
2
0.57
6.13
0.1
19.565
Leaves
3
0.57
0.16
0.1
i a.497
Stems
1
1.43
1.18
0.07
14.826
Stems
2
1.43
124
0.07
12.046
Stems
3
1.43
1.28
0.07
10.193
Rwls
1
2
1.35
0.23
2.556
Roots
2
2
1.33
023
2.502
Roots
3
2
1.34
023
2.474
NC-7
Leaves
1
0.57
0.49
0.09
7.16
Leaves
2
0.57
0.47
0.09
8.003
Leaves
3
0.57
0.48
0.09
7.561
Stems
1
1.43
123
0.07
12.15
Stems
2
1.43
1.25
0.07
Il25
Slems
3
1.43
129
0.07
9.45
ROoki
1
2
121
024
2161
Rwts
2
2
1.39
024
1.783
Rwts
3
2
126
0.24
2.056
NC-l 1 Leaves
1
0.57
0.52
0.16
8.457
Leaves
2
0.57
0.51
0.16
a.86
Leaves
3
0.57
0.53
0.16
8.054
Stems
1
1.43
1.33
0.04
62
Slems
2
1.43
1.37
0.04
4.428
Slems
3
1.43
1.35
0.04
5.314
ROOtS
1
2
1.73
0.u
1.6
ROC&
2
2
1.65
0.44
1.78
ROOt!S
3
2
1.67
0.44
1.735

---

Table F. Continued
Sampling Date Cultivar Residue Replicale Initial weight Final weight Ash
m,Bss loss
(SI
(9)
(s)
PJ>
03/29/94
Florunner Leaves
1
0.57
0.15
0.1
4.268
Leaves
2
0.57
0.26
0.1
:3.365
Leaves
3
0.57
0.24
0.1
:3.529
Slems
1
1.43
0.66
0.07
3.08
Stems
2
1.43
0.6
0.07
3.3
Stems
3
1.43
0.59
0.07
:3.336
Roots
1
2
1.43
0.23
'1.973
Roots
2
2
1.6
0.23
‘1.553
ROob
3
2
1.64
0.23
‘1.455
NC-7
Leaves
1
0.57
0.4
0.09
:2.166
Leaves
2
0.57
0.31
0.09
2.916
Leaves
3
0.57
0.32
0.09
:2X33
Slems
1
1.43
0.44
0.07
:3.88ô
Stems
2
1.43
0.55
0.07
:3.463
Slems
3
1.43
0.54
0.07
3.52
;Roots
1
2
0.7
0.24
:3.781
Roots
2
2
0.73
0.24
:3.707
Roots
3
2
0.69
0.24
3.805
N C - 1 1 L e a v e s
1
0.57
0.3
0.16
3.239
Leaves
2
0.57
0.21
0.16
:3.917
Leaves
3
0.57
0.39
0.16
;2.561
Stems
1
3.43
0.56
0.04
:3.w
!Stems
2
1.43
0.61
0.04
:3.217
Stems
3
1.43
0.65
0.04
:3.068
ROOtS
1
2
1.56
0.44
'1 383
ROOts
2
2
1.06
0.44
:3.cm
RoOts
3
2
1.37
0.u
2.41

---

152
Table G. Mass loss of sorghom residue.
Ssmpiing D a t e Cultivar
Residue Replicate Initial weight Final weight As41
mass loss
Cs)
(SI
@)
(%)
01/07/94
Triumph-266 Leaves
1
0.85
0.66
0.2
13.705
Leaves
2
0.85
0.7
0.2
12.3
Leaves
3
0.85
0.82
0.2
8.082
Slems
1
1.15
0.97
0.07 9.118
Stems
2
1.15
1.05
0.07 6.2
Stems
3
1.15
0.81
0.07 14.954
Roots
1
2
1.72
0.34
4.928
Roots
2
2
1.69
0.34 5.166
Roots
3
2
1.72
0.34 4.928
GW-744BR Leaves
1
0.85
0.57
0.11 13.467
Leaves
2
0.85
0.52
0.11 15.216
Leaves
3
0.85
0.46
0.11 17.291
Slems
1
1.15
0.98
0.1
12.18
Stems
2
1.15
1.02
0.1 9.68
Stems
3
1.15
0.97
0.1
11.76
Rot%s
1
2
1.49
0.3
5.036
RO0ts
2
2
1.07
0.3
3.910
Roots
3
2
1.64
0.3
4.103
NKing-300 Leaves
1
0.85
0.8
0.14
8.047
Leaves
2
0.85
0.74
0.14
9.141
Leaves
3
0.85
0.74
0.14
9.141
Stems
1
1.15
1.05
0.05 5.862
Stems
2
1.15
1.04
0.05 6.253
Sterns
3
1.15
1.01
0.05 7.425
ROOG
1
2
1.7
02 3.84
Roots
2
2
1.71
02
3.764
Roots
3
2
1.5
02
5.377
Sampling Date
Cultivar
Residue Replicate Initial weight Final weight Ash mass kkss
&Il
&Il
(8)
fw
Olll il94
Triumph-266 Leaves
1
0.85
0.6
02
15.814
Leaves
2
0.85
0.61
02
15.462
Leaves
3
0.85
0.6
02 15.814
Sterns
1
1.15
1.08
0.07
5.146
Stems
2
1.15
0.0
0.07 11.672
Stems
3
1.15
0.91
0.07 11.307
Roots
1
2
l.CA
0.34 8.358
RCKb
2
2
1.61
0.34 5.6a2
ROOts
3
2
1.71
0.34
5.007
GW-744BR Leaves
1
0.85
0.51
0.11 15.562
Leaves
2
0.85
0.43
0.11 18.329
Leaves
3
0.85
0.45
0.11 17.637
Stems
1
1.15
0.n
0.1
20.16
Stems
2
1.15
0.88
0 . 1
15.51
Stems
3
1.15
0.72
0.1 2226
RoOts
1
2
1.53
0.3
4.787
ROOts
2
2
1.03
0.3
4.165
ROC&
3
2
1.65
0.3
4.041

---

153
Table G. IContinued
NKing-300
Leaves
1
0.85
0.68
0.14
il.335
Leaves
2
0.85
0.6
0.14
14.26
Leaves
3
0.85
0.6
0.14
14.26
Stems
1
1.15
1.04
0.05
6.253
Slems
2
1.15
0.86
0.05
'13.253
stems
3
1 .lS
1
0.05
7.816
ROOts
1
12
1.47
02
5.607
Rools
2
2
1.49
0.2
5.454
RCKJts
3
;2
1.56
02
4.916
Sampling Date
Cuttivar
Residue Replicate Initial weight Final weight Ash
massloss
@)
(a)
@)
C%l
OI/1 MU
Triumph-266 Leaves
1
0.85
0.62
0.2
15.111
Leaves
2
0.85
0.58
0.2
16.517
Leaves
3
0.85
0.51
02
,18.977
Stems
1
1.15
0.84
0.07
13.86
Slems
2
1.15
0.69
0.07 19.331
Stems
3
1.15
0.83
0.07
14.225
Rools
1
<2
1.41
0.34
7.392
Roots
2
.2
1.65
0.34 5.484
Ro&i
3
;2
1.53
0.34
6.438
GW-744BR Leaves
1
0.85
0.U
0.11 17.983
Leaves
2
0.85
0.42
0.11 18.875
Leaves
3
0.85
0.35
0.11 :21.095
Stems
1
1.15
0.8
0.1
18.9
Stems
a
1.15
0.74
0.1
21.42
Stems
3
1.15
0.64
0.1
25.62
Rools
1
2
1.56
0.3
4.478
Rwts
2
2
1.65
0.3
4.041
RWtS
3
2
1.46
0.3 5.222
NKing-300 Leaves
1
0.85
0.53
0.14
16.82
Leaves
2
0.85
0.73
0.14
9.507
teaves
3
0.85
0.55
0.14 16.068
Stems
1
1.15
0.37
0.05
8.989
Stems
2
1.15
0.83
0.05
14.48
Stems
3
l-15
0.88
0.05 12506
Rods
1
2
1.53
02
5.140
Rods
a
2
1.44
02 5.638
RtMS
3
2
1.43
02
5.915
Sampling Date Cultivar
Rsidue Repldte Initialweight Fïnalweight iw mass IOS
(0)
(s)
(Q)
cw
02/01!94
Triumph-266
Leaves
1
0..85
0.u
02
21.437
Leaves
2
0.85
0.44
02
21.437
Leaves
3
0.85
0.41
02
22.491
Stems
1
l"l5
0.74
0.07
17.508
Stems
2
1.15
0.58
0.07
23.344
Stems
3
1.15
0.74
0.07
17.508
Roots
1
2
1.34
0.34
7.948
ROOb
2
2
1.4
0.34
7.471
ROots
3
3
4.
1.55
0.34
6279

---

Table G. Continued
GW-744BR L e a v e s
1
0.85
0.32
0.11
22.133
Leaves
2
0.85
0.3
0.11
22.825
Leaves
3
0.85
0.3
0.11
22.825
Stems
1
1.15
0.6
0.t
27.3
Stems
2
1.15
0.63
0.1
26.04
Stems
3
1.15
0.72
0.1
2226
Roots
1
2
1.3
0.3
6.217
Ro~ts
2
2
1.26
0.3
6.499
Roots
3
2
1.31
0.3
6.155
NKing-300 L e a v e s
1
0.85
0.37
0.14
22.67
Leaves
2
0.85
0.4
0.14
21.573
Leaves
3
0.85
0.52
0.14
17.185
Slems
1
1.15
0.81
0.05
15242
Stems
2
1.15
0.68
0.05
20.323
Stems
3
1.15
0.81
0.05
15.242
ROOts
1
2
1.71
0.2
3.764
Roots
2
2
1.43
0.2
5.915
Roots
3
2
1.21
0.2
7.605
Sampling Date Cultivar
Residue Replicate Initial weight Final weight Ash
mass loss
@)
@)
02)
QQ
03/01/94
Triumph-266 Leaves
1
0.85
0.48
0.2
9.174
Leaves
2
0.85
0.61
0.2
7.081
Leaves
3
0.85
0.48
02
9.174
Stems
1
1.15
0.69
0.07
7.351
Stems
2
1.15
0.84
0.07
8.034
Stems
3
1.15
0.75
0.07
6.51
ROOts
1
2
1.33
0.34
7.204
Rods
2
2
1.1
0.34
8.955
ROOtS
3
2
1.25
0.34
7.872
GW-744BR L e a v e s
1
0.85
0.44
0.11
9.154
Leaves
2
0.85
0.5
0.11
8.097
Leaves
3
0.85
0.88
0.11
5.281
Stems
1
1.15
0.56
0.1
9.328
Stems
2
1.15
0.41
0.1
11.356
Stems
3
1.15
0.47
0.1
10.545
RQOts
1
2
1.06
0.3
9.111
ROOiS
2
2
1.08
0.3
8.984
ROOtS
3
2
1.25
0.3
7.715
NKing-300 Leaves
1
0.85
0.68
0.14
5.633
Leave-s
2
0.85
0.56
0.14
7.34
Leaves
3
0.85
0.57
0.14
7.109
Slems
1
1.15
0.58
0.05
8.731
Stems
2
1.15
0.68
0.05
7.8Q5
Stems
3
1.15
0.58
0.05
8.731
ROOts
1
2
127
0.2
7.144
Rwts
2
2
1.22
0.2
7.528
ROOts
3
2
0.95
02
9.602

---

155
Table G. Continued
Sampling Date Cultivar
Residue Replicate Initial weight Final weight Ash
lmssloss
cér)
@)
@)
t-W
03/29/!34
Triumph-266 Leaves
1
0.85
0.54
0.2
8.208
Leaves
2
0.85
0.54
0.2
8.028
Leaves
3
0.85
0.67
0.2
6.118
Stems
1
1.15
0.75
0.07
6.51
Slems
2
1.15
0.8
0.07
5.810
Stems
3
1.15
0.74
0.07
6.649
Rwîs
1
2
1.62
0.34
52
Roots
2
2
1.26
0.34
7.655
Hoots
3
2
128
0.34
7.655
GW-744BR Leaves
1
O"85
0.78
0.11
3.166
Leaves
2
0.,85
0.47
0.11
8.626
Leaves
3
0.25
0.48
0.11
8.802
Stems
1
l..lS
0.46
0.1
10.41
Stems
2
1..15
0.42
0.1
11221
Stems
3
l..lS
0.38
0.1
11.762
uoots
1
2
1.06
0.3
g.111
ROOtS
2
2
1.12
0.3
8.07
ROOtS
3
2
1.14
0.3
8.523
NKing-300 Leaves
1
0.85
0.5
0.14
8.364
Leaves
2
0.85
0.84
0.14
5.974
Leaves
3
0.85
0.86
0.14
5.633
Stetns
1
l-15
0.54
0.05
9295
Stems
2
l..lS
0.83
0.05
8.027
Sterns
3
1.15
0.56
0.05
9.013
ROMS
1
2
12
02
7.#1
Hoots
2
2
1.14
02
8.142
mots
3
2
1.73
02
3.61

---

Table H. Chage in specific surface area of cotton residue.
Sampling Oak
Cuftivar Residue Replicate Specifïc surface Area
(mm??)
0 1107194
OLP-5690 Leaves 1
1783.964
Leaves 2
1688.235
Leaves 3
1723.844
Stems 1
1031.305
Stems 2
1035.622
Sterns 3
940.264
OP-5215 Leaves 1
1812.851
Leaves 2
1796.842
Leaves 3
1842.36s
Stems
1
853.434
Stems
2
938.412
Stems
3
852.915
HS-46
Leaves 1
1771.404
Leaves 2
1695.231
Leaves 3
1668.254
Stems 1
775.698
Sterns 2
814.905
Sterns 3
689.361
Sampling Date Cuttivar Residue Replicate Specifïc surface Area
(mmA2)
01/11/94
OLP-5690 Leaves 1
1669.529
Leaves 2
1685.623
Leaves 3
1704.653
Stems
1
914.833
Stems 2
9 1 2 3 0 4
Slems
3
898.732
OP-5215 Leaves 1
1653,623
Leaves 2
1689.874
Leaves 3
1656.231
Sterns 1
826.172
Stems 2
850.168
stefns
3
812.426
HS-46
Leaves 1
1599.632
Leaves 2
1687231
Leaves 3
1653.966
Stems 1
794.396
Stems
2
731.05
Stems
3
742.116
Sampling Date
Cuttivar Residue Replicate Specifc surface Area
(mm*2)
01/18/94
OLP-6690 Leaves 1
1564.326
Leaves 2
1661258
Leaves 3
1 6 1 2 2 5 8
Slerns
1
930.92
Stems
2
802.536
Slems
3
759.599
OP-5215 Leaves 1
1563.256
Leaves 2
1602.365
Leaves 3
1699.532

---

157
Table H. Continued.
Stems
1
850.764
Stems
2
756.851
Stems
3
730.421
HS-46
Leaves
1
,1498.032
Leaves
2
1562.358
Ceaves
3
1586.652
Stems
1
786.572
Stems
2
702.305
Stems
3
728.235
Sampling Date Cultivar
Residue
Repkate Speùfic surface Afea
(mm*2)
02/01/94
OLP-5690
Leaves
1
1532.898
Ceaves
2
1 5 2 4 . 8 3 2
Leaves
3
1499.362
Stems
1
8 7 1 . 1 8 2
Slerns
2
805.519
Stems
3
825.423
DP-521 5
Leaves
1
1542.632
Leaves
2
1488.632
Leaves
3
1586.362
Stems
1
719.324
Stems
2
798.262
Stems
3
711.258
Hs-46
Leaves
1
1423.632
Leaves
2
1399.865
Leaves
3
1402.362
Stems
1
752.282
Stems
2
663.487
Stern-s
3
701.589
Sampling Date Cultivar
Residue
Replide
Specifïc surface Area
(rnm”2)
03/Ol!Q4
OLP-5690
Leaves
1
1399.651
Leaves
2
1465.654
Leaves
3
1423.656
Stems
1
720.97
Stems
2
772.329
Stems
3
805.654
DP-521 5
Leaves
1
1265.632
L.eaves
2
1356.987
L.eaves
3
1363.52
Stems
1
775.231
Stems
2
683.739
Stems
3
702.532
HS-46
Leaves
1
1399.12
Leaves
2
1289.365
Leaves
3
1352.654
Sien-s
1
666.539
Stems
2
688.379
Sterns
3
674.235

---

Table H. ContinuecI.
Sampling Date Cultivar Residue
Replicate Specifïc surface Area
(mmA2)
03/29/94
OLP-5690 Leaves
1
1285.657
Leaves
2
1301.562
Leaves
3
1289.365
Slerns
1
688.201
Stems
2
650.816
Slems
3
683.338
D P - 5 2 1 5 L e a v e s
1
1288.741
Leaves
2
1286.365
Leaves
3
1198.562
Sterns
1
657.293
Stems
2
728.534
Slems
3
709.445
HS-46
Leaves
1
1285.632
Leaves
2
1186.235
Leaves
3
1254.238
Stems
1
629.381
Stems
2
640.825
Stems
3
659.024

---

159
Table 1. Change in specific surface area of peanut feMue.
Sampling Date Cuttivar Residue
Replicale Speciitïc surface Area
0-nn-W
01/07/94
Florunner Leaves
1
2250.229
Leaves
2
2250.942
Leaves
3
2394.624
Stems
1
1500.112
Slems
2
1500.628
Stems
3
1596.416
NC-7
baves
1
1603.049
Leaves
2
1590.483
Leaves
3
1481.607
Stems
1
1068.699
Slems
2
1060.3z
Stems
3
987.738
NC-l 1
Leaves
1
2094.639
Leaves
2
2161.695
Leaves
3
2116.055
Stems
1
1396.426
Slems
2
lU1.13
Slems
3
1410.704
Sampiinlg Date Cultivar Residue
Replicate Specifïc surface Area
(mm*2)
0111 II94
Florunner Leaves
1
1691.45
Leaves
2
1633.52
Leaves
3
1887.548
Stems
1
1127.833
Stems
2
1089.013
sems
3
1258.365
NC-7
Leaves
1
1501.869
Leaves
2
1500.912
Leaves
3
1481.343
Slems
1
1001248
Stems
2
1ooo.608
Stems
3
987.562
NC-11
Leaves
1
2024.5’71
Leaves
2
2133.938
Leaves
3
2035.256
Stems
1
1349.718
Stems
2
1422.825
Stems
3
1356.837
Sampling Date Cultivar Residue
Repkate Specifc sutface Area
WV
Ot/l W94
Florunner Leaves
1
1432.442
Leaves
2
1507.52
Leaves
3
2110.135
Stems
1
954.981
Stems
2
1005.013
Stems
3
1406.757
NC-7
Leaves
1
1450.69
Leaves
2
1343.436
Leaves 3
1428.367

---

160
Table 1. Confinued.
Stems
1
967.120
Stems
2
895.623
Stems
3
952.258
NC-11
Leaves
1
1929.202
Leaves
2
1489.548
Leaves
3
1538.488
Stems
1
1286.135
Stems
2
993.03 1
Stems
3
1025.659
Sampling Date Cuftivar Residue
Repkate Spetific surface Area
(mmV
02/01194
Fiorunner L e a v e s
1
1297.958
Leaves
2
1368.958
Leaves
3
1414.867
Stems
1
865,305
Stems
2
912.6384
Stems
3
943.256
N C 7
leaves
1
1405.664
Leaves
2
1369.728
Leaves
3.
1405.668
Stems
1
937.122
Stems
2
926.465
Stems
3
937.125
NC-1 1
Leaves
1
1629.843
Leaves
2
1478.431
Leaves
3
1501.684
Stems
1
1066.562
Stems
2
985.621
Stems
3
1001.123
Sampling D a t e Cutivar Residue
Replicate SpecifkwfaceAm
(mm"2)
03/01/94
Flonrnner L e a v e s
1
1297.957
Leaves
2
1368.957
Leaves
3
1414.867
Stems
1
665.305
Stems
2
912.638
Stems
3
943.258
NC-7
Leaves
1
1377.768
Leaves
2
1349.84a
Leaves
3
1216.284
Stems
1
918.511
Stems
2
899.898
Stems
3
810.856
NC-1 1
Leaves
1
1624.731
Leaves
2
1479.354
Leaves
3
1494.387
Stems
1
1063.154
Stems
2
986.236
Stems
3
996.256

---

161
Table 1. Continued.
Sampling ;Date Cuttivar Rasidue Replicale Spetifie sutface Area
(mm*21
0329194
Florunner Leaves
1
1254.329
Leaves
2
1287.852
Leaves
3
1297.987
Stems
1
838.219
Stems
2
845.235
Slems
3
B65.125
NC-7
Leaves
1
1254.32
Leaves
2
1281.192
L.eaves
3
1216.537
Stems
1
836.213
Stems
2
854.128
Stems
3
811.025
NC-1 1
L.eaves
1
1591.717
L.eaves
2
1437.391
Leaves
3
1494.048
Stems
1
1061.145
!;tem.s
2
958.261
!;tems
3
y96.031

---

162
Table J. Change in specifïc surface area of sorghum residue.
Sampling Date
Cultivar Residue
Replicate
SpecificsurfaceArea
(mti2)
01107194
Triumph-266 Leaves
1
2371.251
Leaves
2
1294.83
Leaves
3
1306.202
Stems
1
1580.634
Stems
2
836.219
Stems
3
870.801
GW-7448R Leaves
1
1628.68
Leaves
2
1859.15
Leaves
3
1377.775
Stems
1
1085.787
Stems
2
1239.433
Stems
3
918.516
NKing-300 Leaves
1
1921.103
Leaves
2
1487.885
Leaves
3
2274.091
Stems
1
1280.735
Slems
2
991.923
Stems
3
1516.061
Sampling Date
Cultivar Residue
Repli&e specifïcswfoceArea
(mM2)
01/11/94
Tdumph-266 Leaves
1
1565.75
Leavw
2
1657.125
Leaves
3
1581.609
Stems
1
1057.167
stems
2
1104.75
Slems
3
1054.539
GW-7448R Leaves
1
1766.847
Leaves
2
1641.172
Leaves
3
1343.953
Stems
1
1177.898
Slems
2
1094.115
Stems
3
895.988
NKing-300 Leaves
1
1512.66
Leaves
2
1431.586
Leaves
3
1487.132
Slems
1
1008.4s
Slems
2
954.39
Slems
3
965.421
Sampling Date
Cuttivar Residue
Replicate
.specifcsthazArea
(mm*3
Ol/laAM
Triumph-266 Leaves
1720.478
Leaves
1494.911
Leaves
139201
Slems
1146.985
Stems
996.607
stm
028.006
GW-7448R Leaves
1393.95
Leaves
1645.371
Leaves
1371.543

---

163
Table J. Contlnued.
Stems
1
929.3
Stems
2
1090.814
Stems
3
914.382
NKing-300
Leaves
1
1703.716
Leaves
2
1360.117
Leaves
3
1290.498
Sien-6
1
1135.81
Stems
2
900.745
Stems
3
860.332
Sampling Date
Cultivar
Residue
Replicate
Specifc surface Area
(mm%
02/0’1/94
Triumph-2M Leaves
1
1914.823
Leaves
2
1340.288
Leaves
3
1307.354
Slems
1
1278.548
Stems
2
893.525
Stems
3
871.569
GW-74413R Leaves
1
13QQ.205
Leaves
2
1229.792
Leaves
3
1300.349
Stems
1
932.803
Stems
2
819.861
Stems
3
866.899
NKing-300
Leave.s
1
1664.187
Leaves
2
1342.443
Leaves
3
1342.872
Stems
1
1109.658
Stems
2
894.982
Stems
3
895247
Sampling Date
Cultivar
Residue
Replicate
Spetific surface Area
(mm*Z)
03/0’l/94
Triumph-:266 Leaves
1
1231.095
Leaves
2
1892.18
Leaves
3
1430.478
Stems
1
820.73
Stems
2
1261.453
Stems
3
953.851
GW-744BR Leavs
1
133.533
Leaves
2
1319.422
Leaves
3
1208.443
Stems
1
887.021
Stems
2
879.632
Slems
3
805.832
NKing-300
Leaves
1
1203.354
Leaves
2
1293.157
Leaves
3
1388.153
Stems
1
802235
stelns
2
882.104
Stems
3
910.788

---

164
Table J. Conlinued.
Sampling Date
Cuttivar
Residue
Repkate Specific surface Area
mm
03/29/94
Triumph-266 Leaves
1
1093.314
Leaves
2
i 507.983
Leaves
3
1288.835
Stems
1
726.876
Stems
2
1005.322
Stems
3
a59223
GW-744BR Leaves
1
1250.348
Leaves
2
1243.08
Leaves
3
1231.973
Stems
1
833.565
Slems
2
828.719
Stems
3
821.315
NKing-300 L e a v e s
1
1302.074
Leaves
2
1254286
Leaves
3
1261.079
Stems
1
868.449
Stems
2
838.19
Stems
3
840.719

---

165
TaMeK. ANOVAforC02evolutionfrom no-tillandpl~~llsamendedwithpeanutresldue.
SOURCE
CIF SS
MS
F
Signifïcant
Soi1
1
9.060368
9.060368
0.05674475
Depth
3
1106.07699
368.69233
2.3OQlM25
- lineai
1
26.849355
20.8493..
0.1681565
-quadratic
1
7.392884
7.392864
0.04830136
- ahic
1
1071.83475
1071.834751
6.7128609
.
SoirDpth
3
4676.36659
i558.7awQ
9.76263418
”
- linear
1
2472.33803
2472.338032
15.4841605
-
- quadratlc:
1
1628.7657
1628.765698
10.2008986
-
- cubic
1
575.261857
575.261857
3.60264340
Err~{a)
16
2554.70163
159.6688456
Tïme
S
11358.725
2271.744999
72.4864128
- linear
1
9058.0113
9058.011295 289.021323
-quadratk:
1
1907.3793
1907.379302 60.8603006
- cubic
1
366.842741
368.842741
11.7689649
-quartic
1
17.187227
17.187227
0.54640681
-quintic
1
7.304431
7.3w31
0.23306841
SoPTime
S
106.522397
21.3044794
0.67977933
-iinear
1
89.455435
89.455435
2.85432722
-quadratïc:
1
15.602814
15.602814
0.49785166
-cubic
1
0.041369
CM41369
0.00131999
-quartic
1
0.093946
0.093946
0.00299761
-quintic
1
1.328833
1.326833
O.M240015
-linearMear
1
1.226565
1.226565
0.03913701
-1ineafquadratic
1
4.QO9641
4.QOQ641
0.1566559
- linearcubic
1
286.681271
286.681271
9.15375372
-quadratic;linear
1
0.076256
0.076258
0.00243316
quadratic"quadratic
1
2.556083
2.556083
0.08155902
quadraWcubic
1
144.013663
144.013833
4.5951673
-a~bic'linear
1
5.070099
5.07oOQQ
o.lslnsn
- cubic'quadratic
1
1.866062
l.fBO62
0.05954196
- cubic'cubic
1
54.063451
54.D6Ml
1.72XkW-4
-quartic'linear
1
18.318810
18.318618
0.5845134
-quartic'quadralic
1
0.42737
0.42737
0.01383644
-quartic'cubic
1
2.226306
2.2263@
0.07103655
-quintic%iear
1
1.416799
1.416799
0.04520698
-quintic*quadratic
1
0.233665
0.233885
0.00745638
-quintic%ubic
1
3.00459
3.00459
0.09588989

---

166
Table K. Conlinued.
SOURCE
DF SS
MS
F
Significant
S ” D ?? ‘I-
15
1600.73547
112.0490311
3.57523944
-
lineaflineaf~inear
1
889.677402
869.677402
2 7 . 7 4 9 5 0 3 2 -
lineaflïneafquadrat
1
361.994844
361.994844
1 1 . 5 5 0 4 6 3 5 -
lineaflineafcubic
1
15.976778
15.976778
0.50978403
lineafquadratic’line
1
159.618111
159.618111
5.093m471
?
lineafquadratic’qua
1
136.314224
136.314224
4.34948866
?
lineafquadratic’cubi
1
26.63316
26.63316
0.84980587
lineafcubic'linear
1
8.394755
8.394755
0.26785827
lineaf cwbic’quadrati
1
48.573996
48.573996
1 S4988994
fineaf wlbic’ahic
1
27.897104
27.897604
0.89013556
lineafquafticlinear
1
9.84662
9.64662
0.30780254
lineafqu~artic’quadra
1
2.809419
2.809419
0.08964241
lineafqu.artic’cubic
1
5.47294
5.47294
0.17462954
lineafqulintic7inear
1
7.347722
7.347722
0.23444973
lineaf quiintic’quadra
1
0.212978
0.212978
0.00679588
lineafquirh’cubic
1
0.165413
0.165413
0.00527797
Enor (b)
80
2507.22298 31.34028725
Tol,al
143
24525.7012
PE (a+b)

---