Ammonia Emissions, Exposed Surface Area, and Crop and Weed Responses Resulting from Three Post-Emergence Slurry Application Strategies in Cereals

Ammonia (NH3) emissions resulting from the field application of livestock slurry has both negative human health and environmental impacts. However, decreasing the exposed surface area (ESA) of slurry upon application can reduce NH3 volatilization by limiting its atmospheric exposure. In the present study, three strategies for depositing slurry within a growing crop were studied, including: 1. standard trailing hoses (SAhose), 2. trailing shoes (SAshoes), and 3. the combination of rigid tines and trailing shoes (SAtines+shoes). Application methods interact with the soil to varying degrees and were evaluated within the context of contemporary weed management practices, namely in cereals receiving inter-row hoeing. SAhose, SAshoes, and SAtines+shoes were compared in three coinciding experiments that assessed slurry ESA, NH3 emissions, and crop and weed effects. SAtines+shoes resulted in smallest ESA, 70–72% and 61–66% less than SAhose and SAshoes, respectively. However, in only one of three site–years did SAshoes and SAtines+shoes reduce NH3 emissions compared to SAhose, by 46% and 29%, respectively. Crop yields, nitrogen (N) accumulation in crop biomass, and intra-row weed biomass were unaffected by the placement method. In heavily crusted soils, the SAtines+shoes prototype worked well; however, the functional differences among placement strategies were not great enough to detect crop and NH3 effects.