Objective The aims were to explore the effects of different proportions of pig manure fertilization on greenhouse gas (N₂O, CH₄ and CO₂) emissions from rice fields in two seasons in Erhai watershed.

Method This study was carried out with the nitrogen input of 180 kg hm⁻² in all fertilization treatments. The five treatments were set up: P1N1 (50% pig manure and 50% chemical nitrogen fertilizer), P2N0 (100% pig manure), P3N0 (150% pig manure), P0N2 (single fertilizer application) and CK (no fertilization, same field management measures). Rice yield, soil chemistry (pH, available potassium, total nitrogen, etc.) and greenhouse gas emissions were monitored, and the warming potential and greenhouse gas emission intensity of rice growing season were estimated.

Results The rice yields of the P1N1 treatment in 2021 a and 2022 a were increased by 28.49% and 43.24% compared with the CK treatment (P < 0.05). The P1N1 treatment significantly increased soil pH and available phosphorus content compared with the P0N2 treatment, and the P3N0 treatment significantly increased soil available potassium and total nitrogen content compared with the P2N0 treatment. Compared with the P0N2 treatment, the P1N1 treatment reduced the N₂O and CO₂ emission fluxes in the paddy field, but increased the CH₄ emission flux. The cumulative emissions of greenhouse gases in the paddy field were mainly the highest during the grain-fertilizer period. The cumulative N₂O emissions of the P1N1 treatment in 2021 a and 2022 a were reduced by 33.73% and 79.32% compared with the P0N2 treatment (P < 0.05). The cumulative CO₂ emissions of P2N0, P3N0 and P0N2 treatments were significantly increased compared with the CK treatment. The cumulative CH₄ emissions of the P1N1 treatment in 2021 a and 2022 a were reduced by 55.28% and 63.30% compared with the P3N0 treatment (P < 0.05). Compared with the P2N0 treatment, the global warming potential of the P1N1 treatment in 2021 a and 2022 a was reduced by 21.63% and 23.10% (P < 0.05), and the soil greenhouse gas emission intensity was reduced by 27.52% and 35.38%. Correlation analysis indicated that pH, total nitrogen, organic matter and available phosphorus were important factors affecting soil greenhouse gas emissions.

Conclusion The combined application of 50% pig manure nitrogen and 50% chemical nitrogen fertilizer is recommended for paddy field fertilization in Erhai Lake basin, which can increase grain yield without increasing the total temperature increasing potential of rice growing season.