Active nitrogen loss mainly includes ammonia (NH₃) volatilization, nitrous oxide (N₂O) emission, NO₃⁻-N and NH₄⁺-N deep leakage (N leaching), and NO₃⁻-N and NH₄⁺-N surface runoff (N runoff), resulting in serious environmental problems. To analyze the characteristics of active nitrogen loss in the four pathways on sloped farmland under conventional fertilization, six lysimeters with a slope of 8° were used. Losses due to NH₃ volatilization, N₂O emission, N leaching, and N runoff were investigated after urea application on a peanut field with red soil in China during the growing season from 2017–2018. Results reveal that at conventional nitrogen levels of 150 and 172 kg hm⁻², the total active nitrogen loss caused by fertilization accounting for the total nitrogen applied was 5.57% and 14.21%, respectively, with the N₂O emission coefficients of 0.18% and 0.10%, respectively; the NH₃ volatilization coefficients of 2.24% and 0.31%, respectively; the N leakage loss rates of 3.07% and 10.50%, respectively; and the N runoff loss rates of 0.08% and 3.30%, respectively. The dry year was dominated by leaching and NH₃ volatilization, while the wet year was dominated by leaching and runoff; the base fertilizer period was dominated by leakage, while the topdressing period was dominated by leakage and runoff, which suggests that the loss of active nitrogen in the soil-peanut system on a sloped red soil was mainly affected by rainfall and fertilization methods. Taken together, reasonable fertilization management and soil and water conservation measures appear to be effective in minimizing the loss of active nitrogen from nitrogen fertilizer.

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.