Dairy Slurry Application Method Impacts Ammonia Emission and Nitrate Leaching in No‐Till Corn Silage

Reducing ammonia (NH 3 ) emissions through slurry incorporation or other soil management techniques may increase nitrate (NO 3 ) leaching, so quantifying potential losses from these alternative pathways is essential to improving slurry N management. Slurry N losses, as NH 3 or NO 3 , were evaluated over 4 yr in south‐central Wisconsin. Slurry (i.e., dairy cow [ Bos taurus ] manure from a storage pit) was applied each spring at a single rate (∼75 m 3 ha −1 ) in one of three ways: surface broadcast (SURF), surface broadcast followed by partial incorporation using an aerator implement (AER‐INC), and injection (INJ). Ammonia emissions were measured during the 120 h following slurry application using chambers, and NO 3 leaching was monitored in drainage lysimeters. Yield and N uptake of oat ( Avena sativa L.), corn ( Zea mays L.), and winter rye ( Secale cereale L.) were measured each year, and at trial's end soils were sampled in 15‐ to 30‐cm increments to 90‐cm depth. There were significant tradeoffs in slurry N loss among pathways: annual mean NH 3 –N emission across all treatments was 5.3, 38.3, 12.4, and 21.8 kg ha −1 and annual mean NO 3 –N leaching across all treatments was 24.1, 0.9, 16.9, and 7.3 kg ha −1 during Years 1, 2, 3, and 4, respectively. Slurry N loss amounted to 27.1% of applied N from the SURF treatment (20.5% as NH 3 –N and 6.6% as NO 3 –N), 23.3% from AER‐INC (12.0% as NH 3 –N and 11.3% as NO 3 –N), and 9.1% from INJ (4.4% as NH 3 –N and 4.7% as NO 3 –N). Although slurry incorporation decreased slurry N loss, the conserved slurry N did not significantly impact crop yield, crop N uptake, or soil properties at trial's end.