Abstract:

Nitrous oxide （N₂O） is one of four the main gases linked to global warming， and agricultural production is the largest anthropogenic source of N₂O emissions. N₂O mainly originates from nitrification and denitrification processes in soil and is predominantly influenced by soil pH value， O₂ concentration， CO₂ concentration， moisture， texture， temperature， and exogenous carbon （C） and nitrogen （N） input. In recent years， China has achieved remarkable results in using green manure to reduce chemical N fertilizer application and drive soil health. However， study of the role of green manure in N₂O emission is still in the early stages. The impact of planting and incorporating green manure on soil N₂O emission depends on factors such as the varieties of green manure and the physicochemical properties of the soil. Among them， the influence on soil mineral N is the greatest factor. Generally， green manure can efficiently absorb soil mineral N in the fallow period， and its incorporation into the soil can reduce chemical N fertilizer application， thus decreasing N₂O emission. However， green manure releases large amounts of N during its decomposition， which may increase soil N₂O emissions. Combined with appropriate N₂O emission reduction approaches， N₂O emission in green manure-based systems can be reduced according to planting systems， crop varieties， climate conditions and soil types. In southern China’s rice-green manure rotation area， chemical N could be reduced by 40%， when adding alkaline amendments such as biochar. In northern China’s main crop-green manure rotation area， chemical N could be reduced by 15%-20%， through adding chemical inhibitors and combining mechanical deep application of chemical N fertilizers. For main crops rotated or intercropped with green manure systems in Northeast and Northwest China， chemical N could be reduced by 13%-48%， by adding nitrification inhibitors， with integrated water-fertilizer management practices and no-tillage. In main crops rotated with green manure systems of Southwest China， chemical N could be reduced by 15%-20%， through techniques such as slow-release fertilization， use of chemical inhibitors， and others. In this study we have focused on the feasibility of N₂O emission reduction by combining green manure practices and exogenous reduction approaches to N₂O emission， to provide practical guidance for reducing N₂O emission in green manure-based systems.

Key words: green manure, nitrous oxide, influencing factors, emission reduction technology