Dairy Slurry Application Method Impacts Ammonia Emission and Nitrate Leaching in No-Till Corn Silage
2011
Powell, J. M. | Jokela, W. E. | Misselbrook, T. H.
Reducing ammonia (NH₃) emissions through slurry incorporation or other soil management techniques may increase nitrate (NO₃) leaching, so quantifying potential losses from these alternative pathways is essential to improving slurry N management. Slurry N losses, as NH₃ or NO₃, 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 m³ 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 NO₃ 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 NH₃–N emission across all treatments was 5.3, 38.3, 12.4, and 21.8 kg ha⁻¹ and annual mean NO₃–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 NH₃–N and 6.6% as NO₃–N), 23.3% from AER-INC (12.0% as NH₃–N and 11.3% as NO₃–N), and 9.1% from INJ (4.4% as NH₃–N and 4.7% as NO₃–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.
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