Jt. Gilmour et al., KINETICS OF CROP RESIDUE DECOMPOSITION - VARIABILITY AMONG CROPS AND YEARS, Soil Science Society of America journal, 62(3), 1998, pp. 750-755
A kinetic description of crop residue decomposition makes assessment o
f the global C cycle and nutrient cycling possible for a wide variety
of crop production systems. It was the objective of this study to comp
are decomposition kinetics of soybean [Glycine max (L.) Merr.], rice (
Oryza sativa L.) and grain sorghum [Sorghum bicolor (L.) Moench.] resi
dues for 3 yr to determine if variability among years was similar to t
hat among crops. Crop residues were incorporated into a Crowley silt l
oam (fine, montmorillonitic, thermic Typic Albaqualf) soil and incubat
ed at 25 degrees C under optimum soil moisture for 54 to 66 d. Initial
(0-2-wk) decomposition was related to crop residue organic N and C/N
ratio, while subsequent decomposition was not related to these factors
. Decomposition data were evaluated using first-order kinetics and seq
uential and simultaneous decomposition models. As a result of the vari
ability among crops and years, which was not related to residue charac
teristics (organic N or C/N ratio), it was concluded that mean estimat
es of rate constants and the rapid fraction would provide a reasonable
estimate of crop residue decomposition for a variety of crops using e
ither decomposition model. For the sequential model, mean rapid- and s
low-fraction rate constants were 0.025 and 0.0091 d(-1), respectively,
while the rapid fraction was 31%. Parallel values for the simultaneou
s model were 0.21 and 0.0080 d(-1) and 20%.