Short-Term Forage Responses, Soil Nitrogen Availability, and Greenhouse Gas Fluxes Under Contrasting Nitrogen Sources in Cool-Season Forage Systems

Nitrogen (N) sources affect forage production, soil N dynamics, and greenhouse gas (GHG) emissions. This study evaluated short-term effects of contrasting N sources on forage responses, soil health indicators, and GHG emissions in a cool-season oat (Avena sativa L.) and annual ryegrass (Lolium multiflorum L.) system. Treatments were T1 (grass only), T2 (grass + N), T3 (grass + legume), T4 (grass + poultry litter), and T5 (grass + cattle dung). Crude protein was greater in T3 than in T4 (18% versus 13%; p = 0.02). In May, T3 had the greatest microbial C:N ratio (60.6) and soil inorganic N (45.5 mg N kg−1; p < 0.01). Potentially mineralizable N was greater in T3 than in T1, T2 and T4 (3.96 versus ≤ 2.71 mg NH4-N kg−1 day−1; p < 0.01). Mean daily CH4 fluxes were greater (p < 0.01) under T5 (1106 g CH4-C ha−1 day−1) than under T1 and T3 (≤−3.59 g CH4-C ha−1 day−1). Mean daily CO2 fluxes were lower in T3 and T4 than in T1, T2, and T5. There were no effects on N2O emissions. Legume integration enhanced short-term N cycling and forage nutritive value, without N2O emissions, over a 60-day experiment.