Rainfall as the Dominant Trigger for Pulse Emissions During Hotspot Periods of N2O Emissions in Red Soil Sloping Farmland

Farmland N2O emissions exhibit significant fluctuations in subtropical regions due to notable seasonal rainfall and temperature variations. The dominant factors influencing N2O emissions in red-soil sloping farmland, which is widely distributed and actively cultivated in the region, remain uncertain. To investigate N2O emission characteristics of red-soil sloping farmland and responses to meteorological and soil environmental variables and tillage practices, a typical planting system (summer peanut-winter rapeseed rotation system) in southern China was selected. Two common soil micro-environments (conventional tillage, CT, n = 6; and conventional tillage with straw mulching, MT, n = 4) were established within this system, and in situ N2O emissions were monitored over two consecutive years using the static chamber–gas chromatography method. The N2O emission peaks across various growing seasons occurred primarily within 1 to 16 days after fertilization. The N2O emission hotspot periods were observed during the first month following fertilization, accounting for 74.13–91.01% of the total emissions during each growing season. Significant interannual variations in seasonal N2O cumulative emissions were observed, whereas no significant difference in cumulative N2O emissions was observed between MT and CT. Changes in weather and soil environment jointly drive the dynamics of N2O emissions from red soil sloping farmland. Rapeseed-season N2O emissions were driven mainly by rainfall and air temperature, whereas peanut-season N2O emissions were also influenced by soil temperature and NO3−-N content at 0–10 cm depths. These findings provide a sound basis for developing eco-agricultural mitigation pathways in subtropical red-soil hilly regions.