Interactive effects of soil texture and salinity on nitrous oxide emissions following crop residue amendment

Abstract

Crop residue amendment is a usual practice in agroecosystem that simulates nitrous oxide (N2O) emission by providing available carbon and nitrogen sources, and offsets the benefit of this management practice in mitigating global warming by increasing soil organic carbon stocks. In the arid region, during the transformation of desert to oasis farmland, soil silt and clay contents and salinity tend to increase with cultivation years, and largely influence the impact of crop straw addition on N2O emission. However, the interaction effects of soil texture and salinity on N2O emissions after crop residue amendment remains unclear. In this study, microcosm experiments were used to investigate the effect of salinity (0.1%, 0.3%, 0.6% and 1.0%) on soil N2O emissions following cotton residue application in sandy clay loam soil and silty clay soil. In the absence of cotton residue, throughout the incubation period, low N2O emissions were observed from the two soils across different salt levels, and the cumulative N2O emissions increased with increasing salinity. The N2O emissions sharply increased following cotton residue amendment, and these emissions varied depending on soil texture and salinity. Increasing soil salinity greatly increased the cumulative N2O emissions from 46.81 to 780.69 μg N kg−1 due to the enhanced nitrogen mineralization and fungal denitrification rates in the sandy clay loam soil; further, in the silty clay soil, emissions increased from 11.81 to 60.74 μg N kg−1 due to the increased nitrification and bacterial denitrification rates. Overall, our results suggest that moderate soil salinization (≥0.6% salt) likely begins to cause a high risk of N2O emission in the field following cotton residue amendment, especially in soil with high sand content as a result of fungal denitrification.