Multi-seasonal nitrogen recoveries from crop residue in soil and crop in a temperate agro-ecosystem

Abstract

In conservation tillage systems, at least 30%of the soil surface was covered by crop residues which generally contain significant amounts of nitrogen (N). However, little is known about the multi-seasonal recoveries of the N derived fromthese crop residues in soil-crop systems, notably in northeastern China. In a temperate agro-ecosystem, 15 N-labeled maize residue was applied to field surfaces in the 1 st year (2009). From the 2 nd to 4 th year (2010-2012), one treatment halted the application ofmaize residue, whereas the soil in the second treatment was re-applied with unlabeled maize residue. Crop and soil samples were collected after each harvest, and their 15 N enrichments were determined on an isotope ratio mass spectrometer to trace the allocation of N derived from the initially applied maize residue in the soil-crop systems. On average, 8.4% of themaize residue N was recovered in the soil-crop in the 1 st year, and the vastmajority (61.9%-91.9%) was recovered during subsequent years. Throughout the experiment, the cumulative recovery of the residue N in the crop increased gradually (18.2%-20.9%), but most of the residue N was retained in the soil, notably in the 0-10 cm soil layer. Compared to the single application, the sequential residue application significantly increased the recovery of the residue N in the soil profile (73.8%vs. 40.9%) and remarkably decreased the total and the initially applied residue derived mineral N along the soil profile. Our results suggested that the residue N was actively involved in N cycling, and its release and recovery in crop and soil profile were controlled by the decomposition process. Sequential residue application significantly enhanced the retention and stabilization of the initially applied residue N in the soil and retarded its translocation along the soil profile. Copyright: