Effects of N levels on land productivity and N2O emissions in maize–soybean relay intercropping

Abstract

BACKGROUND: Relay intercropping of maize and soybean can improve land productivity. However, the mechanism behind N2O emissions in this practice remains unclear. A two-factor randomized block field trial was conducted to reveal the mechanism of N2O emissions in a full additive maize–soybean relay intercropping. Factor A was three cropping systems – that is, monoculture maize (Zea mays L.), monoculture soybean (Glycine max L. Merr.) and maize–soybean relay intercropping. Factor B was different N supply, containing no N, reduced N and conventional N. Differences in N2O emissions, soil properties, rhizosphere bacterial communities and yield advantage were evaluated. RESULTS: The land equivalent ratio was 1.55–2.44, and the cumulative N2O emission ((Formula presented.)) was notably lower by 60.2% in intercropping than in monoculture, respectively. Reduced N declined (Formula presented.) without penalty on the yield advantages. The relay intercropping shifted soil properties – for example, soil organic matter, total N, (Formula presented.) and protease activity – and improved the soil microorganism community – for example, Proteobacteria and Acidobacteria. Intercropping reduced (Formula presented.) by directly suppressing nirS- and amoA-regulated N2O generation during soil N cycling, or nirS- and amoA-mediated soil properties shifted to reduce (Formula presented.) indirectly. Reduced N directly reduced (Formula presented.) by decreasing soil N content and reducing soil microorganism activities to alleviate N2O produced in soil N cycling. CONCLUSION: Conducting a full additive maize–soybean relay intercropping with reduced nitrogen supply provides a way to alleviate N2O emissions without the penalty on the yield advantage by changing rhizosphere bacterial communities and soil N cycling. © 2024 Society of Chemical Industry.