How incorporation depth of corn straw affects straw decomposition rate and C&N release in the wheat-corn cropping system

Abstract

The effects of straw incorporation on soil characters are well known, however, straw incorporation depth impact on corn straw decomposition rate, microbial biomass carbon (MBC) & microbial biomass nitrogen (MBN), soil carbon (C) and nitrogen (N) concentration during straw decomposition have not been documented. A two-year field experiment was carried out in a wheat-corn cropping system to investigate the effects of straw incorporation depth on decomposition rate of corn straw and soil C and N release. The straw incorporation depths were: topsoil 0–10 cm (TI), medium depth 10–20 cm (MI), and deep depth 20–30 cm (DI). The results showed that corn straw decomposition rate was significantly higher in TI by 24.5 % and 16.5 % than in MI and DI treatments from October 2016 to August 2017. The average contents of MBC and MBN during the decomposition period of straw were higher in TI than in MI and DI treatments (P < 0.01). Additionally, the release of N and C from the corn straw was higher in TI, causing a significantly higher average concentration of NO3−–N (P < 0.01) and total organic carbon (P < 0.05) observation in this layer compared with MI and DI. Our results suggest that the corn straw incorporation in topsoil layer of 0–10 cm can decompose faster, and the higher decomposition rate may facilitate the release of C&N from the straw, causing the higher availability of mineral nitrogen and total organic carbon of this layer.