Zeolite application mitigates NH 3 and N 2 O emissions from pig slurry-applied field and improves nitrogen use efficiency in Italian ryegrass-maize crop rotation system for forage production.

The present study aimed to assess the efficiency of zeolite in mitigating the nitrogen (N) losses through ammonia (NH ₃ ) and nitrous oxide (N ₂ O) emissions from pig slurry (PS) applied to Italian ryegrass (IRG)-maize fields under a crop rotation system and the consequent effect on nitrogen use efficiency (NUE) for forage production. PS was applied at rates of 150 and 200 kg N ha ^-1 for the IRG and maize growing seasons, respectively, with or without zeolite. Soil mineral N content and NH ₃ and N ₂ O emissions were measured periodically throughout the year-round cultivation of IRG and maize. Forage yield and nutritional composition were also analyzed at the harvest time of each crop. The PS with/without zeolite application effects were interpreted by comparison with those obtained for the negative control (no-N fertilization). Soil ammonium (NH ₄ ⁺ ) content in the PS-applied plots sharply increased within the first week, then progressively decreased in both the IRG and maize growing seasons. Soil NH ₄ ⁺ contents in the zeolite-amended plots were higher compared to the treatment without zeolite except for the first 1 or 2 weeks after PS application when soil nitrate (NO ₃ ^- ) contents significantly decreased. The increase in soil NH ₄ ⁺ content as affected by zeolite application was more distinct in the maize growing season than in the IRG growing season. NH ₃ emission was predominant at the early 2 weeks after PS application. Zeolite application reduced the cumulative emission of NH ₃ from PS by 16.7% and 24.4% and that of N ₂ O by 15.6% and 31.5% in the IRG growing and maize growing seasons, respectively. NUE for dry matter (DM) and total digestible nutrients (TDN) production significantly improved in annual yield basis of the IRG-maize cropping. Zeolite application in PS-applied field may represent effective management in mitigating N losses through odorous NH ₃ and greenhouse gas (N ₂ O) emissions, thereby improving NUE forage production.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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