Rain regime and soil type affect the C and N dynamics in soil columns that are covered with mixed-species mulches
Résumé
The role of precipitation on the decomposition of residue mulches is of primary importance for the adequate management of nutrients in no-tilled agrosystems. The objective of this work was to understand the interactions between water dynamics and crop residue quality and their effect on carbon (C) and nitrogen (N) mineralization. The decomposition of two residue mixtures (wheat + alfalfa and maize + lablab) left at the surface of repacked soil columns, was studied under controlled conditions, at 20 A degrees C over 84 days. Simulated rain pulses were either light and frequent or heavy and infrequent. A loamy soil (Luvisol) and a sandy soil (Ferralsol) were used. The maize/lablab mulch remained wetter between rain pulses which induced greater decomposition than the wheat/alfalfa mulch. Frequent/light rain pulses maintained the mulches wetter between pulses than infrequent/heavy rain pulses, and therefore these mulches decomposed faster. The loamy soil favored the moistening of the mulch layer in contact with the soil which enhanced its decomposition, compared to the sandy soil. The water dynamics (water content of the mulches and soil, evaporation, and drainage) was highly modified by residue quality, rain regime and soil type, which in turn significantly affected the mineralization of C and N.