Effects of N levels on land productivity and NO emissions in maize-soybean relay intercropping.

Background: Relay intercropping of maize and soybean can improve land productivity. However, the mechanism behind NO emissions in this practice remains unclear. A two-factor randomized block field trial was conducted to reveal the mechanism of NO 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 NO emissions, soil properties, rhizosphere bacterial communities and yield advantage were evaluated.

Results: The land equivalent ratio was 1.55-2.44, and the cumulative NO emission ( ) was notably lower by 60.2% in intercropping than in monoculture, respectively. Reduced N declined without penalty on the yield advantages. The relay intercropping shifted soil properties - for example, soil organic matter, total N, and protease activity - and improved the soil microorganism community - for example, Proteobacteria and Acidobacteria. Intercropping reduced by directly suppressing nirS- and amoA-regulated NO generation during soil N cycling, or nirS- and amoA-mediated soil properties shifted to reduce indirectly. Reduced N directly reduced by decreasing soil N content and reducing soil microorganism activities to alleviate NO produced in soil N cycling.

Conclusion: Conducting a full additive maize-soybean relay intercropping with reduced nitrogen supply provides a way to alleviate NO emissions without the penalty on the yield advantage by changing rhizosphere bacterial communities and soil N cycling. © 2024 Society of Chemical Industry.