Biochemical Quality of Crop Residues and Carbon and Nitrogen Mineralization Kinetics under Nonlimiting Nitrogen Conditions

International audienceStatistical relationships were established between the fate of C and N from 47 types of crop residues and their biochemical characteristics during a soil incubation at 15°C. The incubations were carried out under nonlimiting N in order to differentiate the effects of biochemical characteristics of residues from those of soil N availability. Depending on the residue, the apparent mineralization of residue C after 168 d varied from 330 to 670 g kg−1 of added C. Mineralization kinetics were described using a two-compartment decomposition model that decomposes according to first-order kinetics. Amounts of C mineralized after 7 d and the decomposition rate coefficient of the labile fraction were related mainly to the soluble C forms of the residue. No statistical relationship was established between the N concentration of residues and their decomposition in the soil. The incorporation of crop residues into soil led to various soil mineral N dynamics. Two residues caused net N mineralization from the time of their incorporation, whereas all the others induced net N immobilization (1–33 g N kg−1 of added C). After 168 d, only residues with a C/N ratio