Location: Northwest Irrigation and Soils Research
2018 Annual Report
Objectives
Objective 1: 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.
Approach
Sustainable crop and dairy production requires efficient nutrient use. Modern dairy farms produce more milk with fewer inputs per unit of milk than farms in the past. Crop yields continue to increase with improved genetics and management. At the same time, nutrient losses to the environment can negatively impact air and water quality. This is especially a concern when concentration of animal production increases the amount of nutrients brought into an area. This project addresses environmental and agronomic issues associated with irrigated crop and dairy production. Specifically, the research seeks to increase crop nutrient use efficiency, minimize nutrient losses and greenhouse gas (GHG) emissions, and reduce occurrence and transport of antibiotics and antibiotic resistance bacteria. The long-term goal of this project is to develop tools to predict nutrient budgets, antibiotic resistance and emissions in the dairy farm-crop production system.
Project objectives will be achieved through several ongoing and new studies conducted at different scales to improve our understanding and management of nutrients, ammonia and GHG emissions, and antibiotic resistant bacteria and genes in dairy and crop production. Research for Objective 1 encompasses six studies evaluating effects of commercial fertilizer with and without nitrification and urease inhibitors, dairy manure, dairy manure compost, and cover crops on gas emissions, soil nutrient cycling, and crop nutrient uptake. Objective 2 contains five studies to evaluate the existence, fate and transport of antibiotics and antibiotic resistant bacteria and genes in soils and surface water. Objective 3 will utilize existing and new data to improve and validate established farm system models that predict nutrient cycling and gas emissions.
Progress Report
In support of Objective 1, work continued to identify the effects of fertilizer source, timing and nitrification and urease inhibitors on greenhouse gas emissions, nutrient cycling, and field scale nutrient budgets. The five-year rotation has been initiated again with greenhouse gas measurements occurring on a regular basis. Emissions were monitored this past winter to determine the effects of freeze thaw on nitrous oxide emissions. In addition, a nitrogen mineralization component was added to this study this year to help evaluate the amount and timing of nitrogen mineralization from manure application.
Greenhouse gas emissions from the first four years of the study were compiled and a manuscript was submitted for review. Manure application increased emissions of both nitrous oxide and carbon dioxide, while in most instances the soils were a sink for methane. Calculated emission factors indicated that 0.13 to 0.24% of total nitrogen applied was lost as nitrous oxide. The overall global warming potential associated with manure application indicated that manure application had a net negative global warming potential while fertilizer application was near neutral. Work continues to determine the effects of manure application on nitrogen mineralization, nutrient cycling in soils and plant nutrient uptake. In addition, collaborators are investigating the effects of manure application on crop quality and insect/disease pressure.
Work continued determining the effects of manure application on continuous corn with a triticale winter cover crop. Manure application increased yields of triticale up to six times compared to plots receiving only fertilizer. Spring nitrate concentrations in soils were also lower in plots with cover crop compared to without cover crop indicating that the triticale is stabilizing nitrate and may be useful for reducing nitrate losses. A nitrogen mineralization component was added to this study this year to help evaluate the amount and timing of nitrogen mineralization from manure application.
Research to determine the effect of nitrogen supply on corn yield and corn nitrogen uptake continued. Collectively during most site years, corn silage and corn grain yields were not responsive to nitrogen application. Data suggests that using the historical nitrogen management approach (pre-season soil testing) is not valid to guide nitrogen management in corn on many fields in Idaho.
The second-year experiment examining the interacting effects of manure and fertilizer on soil nitrogen mineralization was initiated on a new set of plots. Laboratory analysis of soil samples is in progress.
In support of Objective 2, antibiotic resistant genes and Polymerase chain reaction methods have been selected but no samples have been sent yet for cross validation. Experiments have been repeated two times, however the results have been inconclusive. There were no significant effects of time, temperature and moisture on antibiotic resistant gene levels in soil, within the specified time frame of the study. Work was completed to determine the occurrence and abundance of antibiotic resistant genes in soil receiving dairy manure and a manuscript was published. This study found that (i) manure application increases antibiotic resistant gene abundances above background soil levels; (ii) the higher the manure application rate, the higher the antibiotic resistant gene abundance in soil; (iii) the amount of manure applied is more important than reoccurring annual applications of the same amount of manure; (iv) absolute abundance and occurrence of antibiotic resistant genes decreases with increasing soil depth, but relative abundances remained constant. This study demonstrated that dairy manure applications to soil significantly increase the abundance of clinically relevant antibiotic resistant genes when compared to control and inorganic fertilized plots.
Work was completed tracking antibiotic resistant genes in soil irrigated with dairy wastewater and a manuscript was published. The key result from this study is that dairy wastewater irrigation significantly enlarges the reservoir of antibiotic resistant genes and intI1 in soils, while detection of these genes rarely occurred in soil irrigated only with canal water.
In support of Objective 3, research was completed to determine baseline emissions of ammonia and greenhouse gasses from western dairy production systems. Two papers have been published related to this work and a third publication is near acceptance. This data has been used to evaluate/validate the Integrated Farm System Model as well as the U.S. Environmental Protection Agency (EPA) methodology for estimating methane emissions from lagoons. The data have been used to evaluate and make improvements in the Intergovernmental Panel on Climate Change methodologies for estimating greenhouse gas emissions from livestock.
An official Ammonia Monitoring Network station was established to contribute to the national database on ammonia concentrations in the U.S. In addition, six other ammonia monitoring stations were established to cover the range of ammonia concentration throughout the Magic Valley in southern Idaho. Work with the EPA has begun to determine ammonia deposition rates within southern Idaho and improve EPA models related to national ammonia emissions and the impacts on air quality.
Accomplishments
1. Applying dairy manure or wastewater to cropland increases the probability of detecting antibiotic resistance genes in the soil. Dairy manure and wastewater are applied to cropland to recycle nutrients but the manure and wastewater contain bacteria, some of which may be classified as antibiotic resistant. ARS scientists at Kimberly, Idaho, conducted studies to measure the occurrence and abundance of antibiotic resistant genes in soil after manure or wastewater application as an indication that antibiotic resistant bacteria may be present. Compared to control (no fertilizer) and conventionally fertilized soils, soils treated with manure or wastewater had significantly higher levels of antibiotic resistant genes. These data advance knowledge that dairy manure and wastewater can enlarge the reservoir of clinically relevant antibiotic resistant genes in soil, which could facilitate acquired resistance in bacteria that are pathogenic to humans and animals.
Review Publications
Niu, M., Appuhamy, J., Dungan, R.S., Kebreab, E., Leytem, A.B. 2017. Effects of diet and manure storage method on carbon and nitrogen dynamics during storage and plant nitrogen uptake. Agriculture, Ecosystems and Environment. 250:51-58.
Dungan, R.S., Snow, D.D., Bjorneberg, D.L. 2017. Occurrence of antibiotics in an agricultural watershed in south-central Idaho. Journal of Environmental Quality. 46:1455-1461. https://doi.org/10.2134/jeq2017.06.0229.
Biswas, S., Niu, M., Pandey, P., Appuhamy, J., Leytem, A.B., Kebreab, E., Dungan, R.S. 2018. Effects of dairy manure storage conditions on the survival of E. coli O157:H7 and listeria. Journal of Environmental Quality. 47:185-189. https://doi.org/10.2134/jeq2017.06.0224.
Dungan, R.S., Mckinney, C.W., Leytem, A.B. 2018. Tracking antibiotic resistance genes in soil irrigated with dairy wastewater. Science of the Total Environment. 635:1477-1483. https://doi.org/10.1016/j.scitotenv.2018.04.020.
Leytem, A.B., Bjorneberg, D.L., Koehn, A.C., Moraes, L.E., Kebreab, E., Dungan, R.S. 2017. Methane emissions from dairy lagoons in western U.S. Journal of Dairy Science. 100(8):6785-6803. https://doi.org/10.3168/jds.2017-12777.
Cassity-Duffey, K., Moore, A., Satterwhite, M., Leytem, A.B. 2018. Nitrogen mineralization as affected by temperature in calcareous soils receiving applications of dairy manure. Soil Science Society of America Journal. 82(1):235-242. https://doi.org/10.2136/sssaj2017.02.0044.
Dungan, R.S., Leytem, A.B., McKinney, C.W., Moore, A. 2018. Occurrence and abundance of antibiotic resistance genes in agricultural soil receiving dairy manure. FEMS Microbiology Ecology. 94(3):1-10. https://doi.org/10.1093/femsec/fiy010.
Leytem, A.B., Bjorneberg, D.L., Moraes, L.E., Kebreab, E., Rotz, C.A., Dungan, R.S. 2018. Ammonia emissions from dairy lagoons in the western U.S. Transactions of the ASABE. 61(3):1001-1015. https://doi.org/10.13031/trans.12646.
