Effects of different types of organic fertilizers replacing chemical fertilizers on ammonia volatilization and greenhouse gas emissions in rice-duck symbiotic system in Erhai Lake Basin

In order to reveal the emission rules and influencing factors of ammonia volatilization (NH₃) and greenhouse gases (N₂O, CH₄, CO₂) in paddy fields with organic fertilizer replacing chemical fertilizer under rice-duck symbiosis in the Erhai Lake Basin, we conducted a randomized block field experiment with ‘Yungeng 37’ rice variety and dry ducks as experimental subjects and equal input of nitrogen of 180 kg·hm⁻². A total of 4 treatments were set up: (1) rice monocropping with no fertilization and no duck (CK); (2) cow dung instead of chemical fertilizer + rice-duck symbiosis treatment (C+D); (3) chicken manure instead of chemical fertilizer + rice-duck symbiosis treatment (P+D); (4) single chemical fertilizer application + rice-duck symbiosis treatment (F+D). Ammonia volatilization and greenhouse gas emissions from paddy fields were monitored after each fertilization, and pH、Eh、NH₄⁺-N and NO₃^--N contents in soil and surface water were measured. The results showed that ammonia volatilization in paddy fields was mainly concentrated within two weeks after fertilization, and the rate of ammonia volatilization reached a peak within 1-3 days after fertilization. Compared with treatment F+D, organic fertilizer instead of chemical fertilizer + rice-duck symbiosis could significantly reduce the ammonia volatilization rate of paddy field by 56.41 % -87.05 %, reduce the accumulation of ammonia volatilization by 95.47 % -98.65 % and volatilization loss by 96.00 % -99.22 %. There was no significant difference between treatment C+D and P+D. Organic fertilizer instead of chemical fertilizer + rice-duck symbiosis significantly reduced 56.71 % -56.93 % of N₂O emission flux and 70.36 % -70.52 % of N₂O cumulative emission in paddy field, significantly increased 136.56 % -182.34 % of CH₄ emission flux and 61.96 % -93.33 % of CH₄ cumulative emission in paddy field, and increased 5.77 % -30.83 % of CO₂ emission flux in paddy field. There was no significant difference in global warming potential (GWP) and greenhouse gas intensity (GHGI) between organic fertilizer instead of chemical fertilizer + rice-duck symbiosis and treatment F+D. The main factors affecting ammonia volatilization were total nitrogen、NH₄⁺-N and NO₃⁻-N concentrations in surface water. The main factors affecting greenhouse gas emissions were soil pH、Eh、NH₄⁺-N、NO₃⁻-N concentrations and rainfall. Under the symbiosis of rice and duck, organic fertilizer instead of chemical fertilizer can significantly reduce ammonia volatilization and N₂O emissions, and chicken manure instead of chemical fertilizer can significantly increase rice yield, which is a sustainable development measure to reduce emissions, increase efficiency and stabilize yield.