Improving Management Practices for Irrigated Western Cropping and Dairy Systems to Contribute to Sustainability and Improve Air Quality

Assess organic and inorganic fertilizer forms and application methods as management options for reducing greenhouse gas emissions, increasing nutrient use efficiencies, and optimizing crop yields for irrigated western cropping systems. Subobjective 1A: Identify effects of fertilizer source, timing and nitrification and urease inhibitors on GHG emissions, nutrient cycling, and field scale nutrient budgets. Subobjective 1B: Identify effects of manure application rate and frequency on GHG emissions, nutrient cycling, and field scale nutrient budgets. Subobjective 1C: Determine the efficacy of cover crops to reduce offsite transport of soil nutrients in a dairy forage crop rotation receiving manure. Subobjective 1D: Evaluate N supply and timing effects on corn yields and nitrogen use. Subobjective 1E: Determine the interacting effects of manure and fertilizer on soil N mineralization. Subobjective 1F: Determine the effects of manure incorporation method and timing on the emissions of CO2 and N2O from moist soils subjected to diurnal freeze-thaw cycles. Objective 2: Investigate the occurrence and transport of antibiotic drugs, antibiotic-resistance genes, and antibiotic-resistant bacteria in irrigated western cropping systems to provide baseline data needed to develop mitigation strategies. Subobjective 2A: Monitor antibiotics in irrigation return waters to better understand their persistence in the environment and potential movement from areas under intensive dairy and crop production. Subobjective 2B: Conduct an inter-laboratory validation of assays to screen selected antibiotic resistance determinants. Subobjective 2C: Determine the influence of dairy manure and compost application rate, soil temperature, and soil moisture content on the occurrence of antibiotic resistant bacteria and antibiotic resistance genes in soil. Subobjective 2D: Evaluate the effect of annual dairy manure applications, as well as crop rotation, on the distribution of antibiotic resistance genes in the soil profile. Subobjective 2E: Determine the prevalence of antibiotic resistant indicator bacteria and antibiotic resistance genes in plots irrigated with diluted dairy wastewater with and without added copper sulfate. Objective 3: Improve measurement and prediction of ammonia and GHG emissions and transport from western dairy systems to improve GHG inventories and evaluate the mitigation potential of management practices. Subobjective 3A: Improve emission factors for NH3 and GHG emissions from western dairy production systems and improve/validate equations and process based models for estimating emissions. Subobjective 3B: Improve understanding of impacts of NH3 losses on regional air quality.