Zeolite application mitigates NH3 and N2O emissions from pig slurry-applied field and improves nitrogen use efficiency in Italian ryegrass-maize crop rotation system for forage production

Abstract

The present study aimed to assess the efficiency of zeolite in mitigating the nitrogen (N) losses through ammonia (NH₃) and nitrous oxide (N₂O) 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 NH₃ and N₂O 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 (NH₄⁺) content in the PS-applied plots sharply increased within the first week, then progressively decreased in both the IRG and maize growing seasons. Soil NH₄⁺ 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 (NO₃^-) contents significantly decreased. The increase in soil NH₄⁺ content as affected by zeolite application was more distinct in the maize growing season than in the IRG growing season. NH₃ emission was predominant at the early 2 weeks after PS application. Zeolite application reduced the cumulative emission of NH₃ from PS by 16.7% and 24.4% and that of N₂O 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 NH₃ and greenhouse gas (N₂O) emissions, thereby improving NUE forage production.

Keywords: Air pollutants; Animal manure; Forage crops; N losses; Zeolite amendment.