Impact of residue addition on soil nitrogen dynamics in intercrop and sole crop agroecosystems

Abstract

Soil nitrogen (N) is one of the most important nutrients for plant productivity and microbial activity in terrestrial ecosystems. However, soil N is also readily affected by land management practices, influencing N2O emissions. This study assessed N dynamics in soil from different crop systems including a 1:2 (one row of maize and two rows soybean) and 2:3 (two rows of maize and three rows of soybean) intercrop and a maize and soybean sole crop as a result of residue addition from maize or soybeans. This was achieved through a 140-day incubation study using δ15N natural abundance. The effect of residue addition on soil TN was greater than its influence on crop systems when compared to treatments with no residue addition (Cont). The influence of residue addition on intercrops was most readily observed in the fractionated soil. Light fraction N (LF-N) and soil microbial biomass N (SMB-N) were significantly greater (p<0.05) in the intercrops than in the sole crops. Residue amended treatments were significantly (p<0.05) depleted in δ15N-TN, δ15N-LF and δ15N-SMB compared to Cont treatments. The δ15N-SMB was significantly enriched (p<0.05) compared to that of the residue, TN and LF-N. Residue amended treatments had significantly lower (p<0.05) N2O emissions than Cont treatments. However, N2O emissions were not significantly different (p<0.05) between soybean and maize amended treatments, nor between intercrops and sole crops. Our results demonstrate that the addition of contrasting residue types influenced short-term N dynamics in intercrops differently than sole crops.