Soil surface management of legume cover has the potential to mitigate nitrous oxide emissions from the fallow season during wheat production

Soil surface management, i.e., mulch by film, straw or cover crop, is very important to water availability in soil on dry lands worldwide, especially during the fallow season, when there is a high concentration of soil nitrate nitrogen (N) to produce nitrous oxide (N2O). To determine whether soil surface management affects N2O emissions during the fallow season, we conducted an experiment to compare N2O emissions from a wheat field that received different surface soil management strategies: control (CK), straw mulch and incorporation (SR), planting legume green manure and incorporation (GM), SR plus GM (SR + GM), and plastic film mulch (FM). The results showed that the average hourly N2O emissions during the fallow season were in the order SR (7.4 mu g N m(-2) h(-1)), GM (10.7 mu g N m(-2) h(-1)), SR + GM (11.7 mu g N m(-2) h(-1)), FM (15.5 mu g N m(-2) h(-1)), and CK (16.4 mu g N m(-2) h(-1)). Correspondingly, reduced total N2O emissions were observed in the SR, GM and SR + GM treatments, with an average reduction of 39.0% (from 302 to 184 g N ha(-1)) while increased N2O emissions were from the GM and SR + GM treatments in the wheat growing season. Additionally, N2O emissions were related to soil nitrate N content, microbial biomass and moisture. Overall, considering N2O emissions, C and N inputs by plant residues and grain yield, the management of GM has the potential to reduce greenhouse gas emissions and improve soil C sequestration and soil fertility. These results emphasized the importance of legume green manure to wheat-fallow cropping systems.