Location: Northwest Irrigation and Soils Research
2019 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
Under Objective 1, the sixth year of a planned eight-year study assessing the effects of manure application rate and timing on greenhouse gas emissions and nutrient cycling was completed. A manuscript detailing the greenhouse gas emissions resulting from this study was published in February of 2019. These data demonstrated that approximately only 0.13 to 0.24% of total nitrogen applied was lost as nitrous oxide gas. The overall global warming potential associated with manure application indicated a net negative global warming potential for manure treatments due to increasing soil organic carbon while the synthetic fertilizer treatment was near neutral.
The third year of a study to determine if cover crops (winter triticale) can reduce offsite transport of nutrients in a dairy forage crop rotation with manure application was completed. Results show that triticale forage yield was 5.5 times greater in plots that receive manure versus those that did not receive manure. The overall harvested forage (corn silage plus triticale) was 2.5 times greater from manured plots with triticale versus plots without manure or triticale. Accordingly, nutrient removal was greater for treatments that had a harvestable cover crop.
Year two of a study to determine the interactions of manure and fertilizer on soil nitrogen mineralization was completed. Soil nitrogen mineralization was monitored in the summer following a late fall manure application to determine if inorganic nitrogen content at the time of manure application influences the mineralization and transport of nitrogen and dissolved organic carbon in the soil. Soil samples from the second site-year were analyzed to assess nitrate, ammonia, and dissolved organic carbon transport through the profile. Net nitrogen mineralization rates were determined over two depths (0-30 centimeter; 30-60 centimeter) and four intervals during the year.
A study evaluating nitrogen supply effects on corn yield and nitrogen use was terminated in FY18 because data analysis from the previous seven site years indicated that the study treatments need to be changed. Corn silage yields did not vary with nitrogen application and corn grain yield seldom increased with nitrogen application. Potential future study treatments and protocols are being evaluated to improve nitrogen fertilizer application recommendations for corn. Data suggest that utilizing only spring soil samples to determine nitrogen fertilizer application rates is not sufficient.
In support of Objective 2, a study to determine the influence of dairy manure application rates, soil temperature, and soil moisture on the occurrence of antibiotic resistant bacteria and genes in soil has been completed. After the soil was amended with dairy manure at agronomic rates, antibiotic resistance genes were tracked under different soil moisture and temperature regimes. Selected antibiotic resistance genes were targeted for investigation because they include resistance to antibiotics that are considered medically important. After a week of incubation, the gene concentrations were found to drop about an order of magnitude, then stabilize for the remainder of the 60-day study. The gene concentrations were not affected by changes in soil moisture and temperature. The data from this short-term study suggest that antibiotic resistance genes are quite resilient in manure-amended soil, while detection of the same genes in soil without manure addition was generally sporadic.
A study to evaluate the effect of dairy manure applications in a crop rotation on the distribution of antibiotic resistance genes in the soil profile has been completed and the results published. This study demonstrated that dairy manure applications to soil significantly increase the abundance of clinically relevant antibiotic resistance genes when compared to control (no fertilizer) and inorganic fertilized plots. Gene abundance was found to be proportional to the amount of manure applied, but in all cases the gene concentrations decreased with increasing depth.
A study to determine the prevalence of antibiotic resistant indicator bacteria and antibiotic resistance genes in soil irrigated with dairy wastewater with and without copper sulfate was completed earlier than anticipated in the project cycle and did not investigate the presence of antibiotic resistant bacteria. In this study, dairy wastewater was used to irrigate soil cropped with wheat. The key result from this study was that dairy wastewater irrigation significantly enlarges the reservoir of antibiotic resistance genes in soil, while detection of these genes rarely occurred in soil irrigated with only water supplied by a canal from the Snake River.
In support of Objective 3, an effort continues to use new and existing dairy emissions data to improve ammonia and greenhouse gas emissions factors and improve/validate equations and process-based models for estimating the emissions. Gas emissions data have been used to help revise/improve equations for estimating greenhouse gas emissions from manure management for the newest assessment by the Intergovernmental Panel on Climate Change (IPCC) as well as the U.S. Environmental Protection Agency (EPA) greenhouse gas inventory. We continue work with a team of scientists developing a new model for estimating farm gas emissions from ruminant animals.
A monitoring effort to quantify ammonia losses from agriculture and the dairy industry continues. Data from a network of monitoring sites in southern Idaho indicates that there is a very high concentration of ammonia in areas with concentrated dairy production. Work to assess the transport and deposition of this ammonia is under way and a dairy site has been identified for measurement of ammonia deposition. Specialized sampling equipment is being assembled and will be deployed to assess ammonia deposition.
Accomplishments
1. Biochar alters soil water retention, greenhouse gas emissions, nutrient cycling, and biology. Because atmosphere-derived carbon in biochar degrades slowly when mixed with soil, biochar can potentially help store carbon in soil. Collaborators at Iowa State University and ARS researchers at six locations across the U.S. completed a project that examined the influence of biochar on soil physical and chemical properties in a broad range of soils. This work, which was reported in 12 publications including a final report completed this year, has had a substantial impact on society’s understanding of biochar as a soil additive. To date, the project’s research papers have been cited by more than 800 publications worldwide. This foundational research provides important guidance to researchers, farmers growing crops on biochar-amended soils, and land managers who wish to evaluate the economic benefits achieved by using biochar to store atmospheric carbon in agricultural soils.
Review Publications
Tarkalson, D.D., Bjorneberg, D.L., Dean, G. 2018. Is static nitrogen management in northwestern U.S. sugarbeet production appropriate? Agricultural and Environmental Letters. 3(1):180001. https://doi.org/10.2134/ael2018.01.0001.
Tarkalson, D.D., Bjorneberg, D.L., Lentz, R.D. 2018. Effects of manure history and nitrogen fertilizer rate on sugar beet production in the northwest U.S. Crop, Forage & Turfgrass Management. 4(1):170083. https://doi.org/10.2134/cftm2017.11.0083.
Arndt, C., Leytem, A.B., Zavala-Araiza, D., Hristov, A., Cativiela, J.P., Conley, S., Daube, C., Faloona, I., Herndon, S.C. 2018. Short-term methane emissions from two dairy farms in California estimated by different measurement techniques and US Environmental Protection Agency inventory methodology: A case study. Journal of Dairy Science. 101(12):11461-11479. https://doi.org/10.3168/jds.2017-13881.
Leytem, A.B., Moore, A.D., Dungan, R.S. 2019. Greenhouse gas emissions from an irrigated crop rotation utilizing dairy manure. Soil Science Society of America Journal. 83:137-152. https://doi.org/10.2136/sssaj2018.06.0216.
Biswanath, D., Rogers, C.W., Leytem, A.B., Schroeder, K.L. 2019. Evaluation of soil test phosphorus extractants in Idaho soils. Soil Science Society of America Journal. 83(3):817-824. https://doi.org/10.2136/sssaj2018.08.0314.
Dungan, R.S., Strausbaugh, C.A., Leytem, A.B. 2019. Survey of selected antibiotic resistance genes in agricultural and non-agricultural soils in south-central Idaho. FEMS Microbiology Ecology. 95(6):fiz071. https://doi.org/10.1093/femsec/fiz071.
