Separate effects of the biochemical quality and N content of crop residues on C and N dynamics in soil
2007
Sall, S. | Bertrand, Isabelle, I. | Chotte, J.L. | Recous, Sylvie | Institut de recherche pour le développement (IRD [Sénégal]) | Unité de Recherche Agronomie Laon-Reims-Mons (UA LRM) ; Institut National de la Recherche Agronomique (INRA)
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Show more [+] Less [-]English. This study assessed the respective roles of biochemical quality and N content of plant residues on C and N dynamics in a soil. Both (15)N- and (13)C-labeled oilseed rape residues (roots, seedpod walls) combining different biochemical characteristics and similar N content or the same biochemical characteristics and different N contents were used as amendments. These treatments were combined with two levels of soil inorganic N to ensure that decomposition was not limited by N availability. The soil was incubated under laboratory conditions for 134 days. Soil amended with residues of similar biochemical quality (i.e. the two pod walls) displayed similar C mineralization dynamics when the initial N availability (residue+soil N) ranged from 1.7 to 3.2% of residue dry matter. The roots showed poorer decomposition than the pod walls, lower cumulative C mineralization and greater accumulation of root-derived C in the > 50 mu m coarse fraction of the soil organic matter. The N content of the residues influenced mineral N accumulation in the soil with a lower net immobilization of residues with low C-to-N ratios. Adding an exogenous source of inorganic N had no effect on C dynamics but modified the remineralization kinetics of the previously immobilized N, suggesting changes in the microbial community involved.
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