Emission of Volatile Organic Compounds as Affected by Rate of Application of Cattle Manure

Abstract

<abstract> Beef cattle manure can serve as a valuable nutrient source for crop production. However, emissions of volatile organic compounds (VOCs) following land application may pose a potential off-site odor concern. This study was conducted to evaluate the effects of land application method, N application rate, soil moisture content, and time since manure application on VOC emissions. Manure from cattle fed a diet containing 30% wet distillers grains was applied to a cropland area at rates required to meet the 0.5, 1, or 2 year N requirement for corn. Land application methods included surface-applying manure (i.e., no tillage) or incorporating manure using disk tillage. The effect of soil moisture content on VOC emissions was determined by adding water to the experimental plots approximately 24 h after manure application. Volatile sulfur compounds (i.e., dimethyl disulfide and dimethyl trisulfide), isovaleric acid, and butyric acid contributed 43.4%, 14.0%, and 13.9%, respectively, of the total measured odor activity value (OAV). Emissions of each of the principal VOC odor compounds were reduced by manure incorporation. In general, no significant differences in VOC measurements of volatile fatty acids (VFAs) and aromatic compounds were found among varying manure application rates. However, an increase in emissions of volatile sulfur compounds resulted from increased manure application. Measurements of VFAs and aromatic compounds usually decreased and sulfide emissions increased following the application of water. Application method, N application rate, soil moisture content, and time since application may all influence VOC emissions following land application of cattle manure.