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 ) and nitrous oxide (N 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 for the IRG and maize growing seasons, respectively, with or without zeolite. Soil mineral N content and NH and N 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 ) 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 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 ) contents significantly decreased. The increase in soil NH content as affected by zeolite application was more distinct in the maize growing season than in the IRG growing season. NH emission was predominant at the early 2 weeks after PS application. Zeolite application reduced the cumulative emission of NH from PS by 16.7% and 24.4% and that of N 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 and greenhouse gas (N O) emissions, thereby improving NUE forage production.