Location: Northwest Irrigation and Soils Research
2025 Annual Report
Objectives
Objective 1: Develop improved practices and strategies for managing inputs in irrigated cropping systems to increase soil health, optimize crop productivity and quality, and minimize negative environmental impacts.
Sub-objective 1A: Identify effects of fertilizer source, timing of application, and nitrification/urease inhibitors on nutrient cycling and field-scale nutrient budgets.
Sub-objective 1B: Identify effects of past manure application rate and frequency on biological indicators of soil health, nutrient cycling, and field-scale nutrient budgets.
Sub-objective 1C: Determine the efficacy of cover crops and minimum tillage to reduce offsite transport of soil nutrients in a dairy forage crop rotation receiving manure.
Sub-objective 1D: Determine the long-term agronomic economic effects of manure applications on crops, soil nutrient (primarily N, C, and P) cycling, and soil health indicators.
Sub-objective 1E: Determine effects of crop rotation, tillage, and residue management on residue breakdown rates and nutrient cycling in irrigated cropping systems.
Sub-objective 1F: Evaluate aboveground biomass yield, forage quality, and nutrient cycling of sorghum-sudangrass hybrids under multiple management practices (row spacing, number of cuttings, and cultivar).
Objective 2: Quantify gaseous emissions from dairy production facilities and manure-amended soils to improve nutrient cycling and reduce environmental impact of these systems.
Sub-objective 2A: Determine the effect of manure application rate and frequency on soil GHG emissions.
Sub-objective 2B: Determine the effect of manure, cover crop, and minimum tillage on soil GHG emissions.
Sub-objective 2C: Determine ammonia transport and dry deposition in the Magic Valley region and improve accuracy of deposition models.
Approach
Resilient irrigated cropping systems in concentrated dairy production regions require proper management of nutrients to maximize agricultural production while minimizing environmental impacts. Dairy farms in the region generally have more cows and produce more milk than in the past. With the increased number of cattle comes an increased production of manure that must be managed. Crop production coexists in the region with a diverse assortment of crops with varying nutrient needs to meet yield and quality goals. The current project will address crop production and environmental issues that results from concentrated dairy and crop production. Broadly, the project objectives are to improve crop nutrient use efficiency, minimize nutrient and greenhouse gas losses to the environment, investigate novel crops, and determine the impact of crop residues in the agroecosystem. These objectives will lead to improved management practices for irrigated cropping systems in semi-arid environments.
Research consists of several continuing long-term studies along with newly developed projects. Objective 1 is focused on how inputs are managed and effect the agroecosystem. The objective is comprised of seven studies. Long-term studies will evaluate the impact of synthetic fertilizers (with and without nitrification inhibitors in one study) and dairy manure on crop response, nutrient cycling, and soil health. New studies will evaluate impacts of novel cropping approaches, including forage cover crops and grasses such as sorghum-sudangrass, on crop production, nutrient cycling, and soil health. Additionally, these studies will address the impact of crop rotation, tillage, and residue management practices on these factors as well. Objective 2 contains three projects focused on determining gaseous emissions from dairy facilities and manure-amended soils. Long term manure application rate effects on greenhouse gas emissions will be studied. A second study will measure the effects of manure, cover crop, and minimum tillage on greenhouse gas emissions. The final project will determine regional ammonia nitrogen transport to improve models that predict ammonia depositions from the atmosphere to the soil surface.
Progress Report
This report documents FY 2025 progress for project 2054-12000-013-000D, “Developing Resilient Irrigated Cropping Systems in Concentrated Dairy Production Areas of the Semi-arid West”, which began in December 2021.
Research continued on Objective 1, “Develop improved practices and strategies for managing inputs in irrigated cropping systems to increase soil health, optimize crop productivity and quality, and minimize negative environmental impacts.” Studies concentrated on addressing the needs of farmers in concentrated dairy production areas of the semi-arid west. To this end, research is focused on nutrient cycling of manure and synthetic fertilizer in crops and soils and developing cropping systems. ARS researchers in Kimberly, Idaho, have made steady progress on addressing these questions that will lead to improvements in management practices to enhance and sustain farm productivity.
A 12-year study focused on understanding soil health and trace gas emissions in relation to varying fertilizer-nitrogen sources and stabilizers as part of the nationwide GRACEnet program was completed. The final spring barley harvest was completed in the fall of 2024. Yield data was collected, and tissue samples were analyzed for nutrient content. This project reached completion as of fall 2024 and a comprehensive dataset has been compiled.
Data on potato yield, quality, and nutrient uptake response during a 12-year manure rate and timing study was published as a peer-reviewed article. This study transitioned into a nutrient drawdown study to investigate the effect of forage crop rotations on soil nutrients. Paired fields are used with spring forage and corn silage in one field and winter forage barley in the second field during this year. All crops were planted and harvested as planned and forage yield/biomass data collected. Forage samples were collected and processed and are being analyzed for nutrient content and forage quality. Soil samples were collected in the spring from the study and were analyzed for nutrient content. The fields have been planted into alfalfa to investigate nutrient removal and yield from legacy manure treatments for one of the major forage crops grown to support dairy production in the region.
Multiple studies have focused on novel cropping systems to improve manure utilization and the overall production environment. Our first study assessed winter forages as cover crop under varied tillage regimes (conventional and minimal). Initial data was published previously, and the field component of the study was completed. These results indicated the value of using winter triticale for forage production in the crop rotation to improve manure utilization. Comprehensive data from this study is being compiled and data analyzed for future publications.
Research on the second cropping system study continued investigating the long-term effects of a single manure application over 10-years prior due to continued observation of treatment effects. The study was impacted by irrigation equipment issues and a critical vacancy. Adjustments to a shorter season and more drought tolerant crop were made to minimize impacts. As such, barley replaced corn for the season, which does not negatively affect the study's objectives. Study treatments were applied in the spring, barley planted, and irrigations are currently being conducted. In early August, the barley will be harvested to determine yields, quality, and nutrient uptake. Initial research from this study focused on changes in soil health metrics was published during this year. Data indicated that soil health metrics were still impacted by manure applications that had occurred over 10-years prior. These results will improve our understanding of soil-system changes and crop production effects that will lead to improved management guidance. Further research data collected from these studies from 2019-2024 is planned to be published in peer-reviewed journals in 2026.
The third study on novel cropping systems for semi-arid irrigated production continued during this year. This study seeks to quantify the impacts of crop rotation, tillage practices, and residue management on agronomic returns and soil function. Dry beans were grown again with improved weed management strategies alongside a new combine that improved our ability to measure both grain and residue yields. Early season soil moisture was enhanced by the no-tillage system. Research also indicated that soil health metrics are slow to change, and incorporated residues decompose quicker than those left on the surface. Yield reductions were seen for no-tillage compared to conventionally managed systems. This study is providing evidence of limitations that exist with conservation practices in terms of both agronomic returns and impacts on soil function.
Research continued in support of Objective 2, “Quantify gaseous emissions from dairy production facilities and manure-amended soils to improve nutrient cycling and reduce environmental impact of these systems." Research on direct measurement of soil gas emissions has been discontinued following the early retirement of the scientist leading the project. Ammonia deposition work was completed using conditional time-averaged gradient (COTAG) systems in major dairy producing regions in southern Idaho. These systems allow the quantification of ammonia deposition and thus, nitrogen additions to soil that are important for accurate management of nitrogen for crop production in the region. Initial data has indicated that ammonia deposition can be a substantial nitrogen addition in certain areas and timeframes and may need to be considered to accurately prescribe fertilizer recommendations in these areas. Cumulative data has been compiled and is currently being analyzed. Results from the dairy-facility portion of this study has been utilized to assess the accuracy of the Surface Tiled Aerosol and Gaseous Exchange (STAGE) model and suggest improvements.
Accomplishments
1. Helping farmers grow healthy, high-fiber food barley through fertilizer management. The nearly $6 billion dollar U.S.A. barley industry is currently focused on malt; however, acreage of barley grown for direct human consumption has increased in recent years due to the release of high-fiber varieties. These new genetics have led to a need to establish nitrogen (N) supplementation recommendations to support crop productivity and farm profitability. ARS researchers in Kimberly, Idaho, and extension scientists from the University of Idaho, investigated food barley response to applied nitrogen at multiple rates and locations. Their work established an N-supply range of 175 to 210 lb N/acre that optimized yields and was used to develop university extension recommendations. These results established fertilizer-N recommendations for food barley that are critical for supporting farmers bottom-line and the overall agricultural economy.
2. More yield, less fertilizer: Improved nitrogen recommendations for Northwest U.S. sugar beet producers. The nearly $3 billion sugar beet industry underwent a transformation during the 2007–2008 growing seasons with the rapid adoption of higher-yielding, herbicide-tolerant varieties. Despite genetic improvements, nitrogen fertilizer continued to be applied based on a yield-goal nitrogen management approach, where the fertilizer rate increased with yield. However, observations indicated these rates were higher than needed, and to address this, research was conducted by ARS scientists in Kimberly, Idaho, in collaboration with Amalgamated Sugar Company agronomists. Researchers determined that a relatively narrow or static range of N management was more appropriate as it optimized yield while reducing fertilizer-N recommendations by up to 60 lbs/acre. This research decreases N-applications compared to the previous method resulting in sustained productivity at decreased input costs for sugar beet producers.
3. More than a byproduct,barley and wheat residues have significant fertilizer replacement value. Large grain yields and residue production of barley and wheat are common in the northwestern U.S. due to favorable growing conditions. While grain is universally removed, farmers need to decide between leaving the residue in the field or selling the straw for other uses. The nutrient cycling implications and fertilizer replacement costs of residue removal have not been well quantified for high yielding barley and wheat grown in the region. To address this ARS researchers in Kimberly, Idaho, and Adams, Oregon, and researchers and extension scientists from the University of Idaho, investigated nearly all classes of wheat and barley across multiple locations and years. Results indicated the cost to replace wheat and barley residue nutrients would range from $50 to 200/acre based on reasonable yield and fertilizer cost ranges. These results provide valuable information to allow farmers to estimate nutrient removal from their crops and better assign a value to their residues to support farm profitability.
4. Determining nitrogen release from manured soils to support crop production. Nearly 40% of U.S. milk production occurs in semi-arid regions, providing an opportunity to recycle manure nutrients through a variety of cropping systems. Accurate prediction of the conversion of organic nitrogen to plant available inorganic nitrogen, termed mineralization, is critical to determine manure application suitability in intensive irrigated agriculture as many crops in the region have quality parameters that are sensitive to nitrogen. ARS researchers in Kimberly, Idaho, developed a nitrogen mineralization model for dairy manure and broadleaf crop residue. This model can be used when making fertilizer recommendations on fields where manure has been applied.
5. Decade-old manure applications still support crop productivity. Nearly 40% of U.S milk is produced in semi-arid environments like those found in southern Idaho, where 375,000 dairy cows are found. While the value of dairy manure as a nutrient source is well established, little information is available concerning soil and biological factors in relation to crop productivity. ARS scientists from Kimberly, Idaho, as part of a nationwide USDA-ARS project, monitored soil fertility-associated biological and chemical properties of recent and past dairy manure applications. Compared to commercial fertilizers, dairy manure positively altered the soil microbiome activity in both the short (1 to 2 years) and long term (11 years) as noted by a study where a single 45 ton/acre manure application without further fertilizer applications was able to match the productivity enhancement of synthetic fertilizer applied annually over four years. Dairy manure applications are a powerful tool for sustaining long-term soil fertility and microbiome vitality for farmers in semi-arid production environments.
Review Publications
Dungan, R.S., Acosta Martinez, V., Lehman, R.M., Manter, D.K., Mikha, M.M., Reardon, C.L., Tarkalson, D.D., Veum, K.S., Weyers, S.L., White, Jr., P.M. 2024. Short-term effects of a heavy dairy manure application on soil chemical and biological indicators in an irrigated semiarid cropping system. Agronomy Journal. 117(1). Article e21737. https://doi.org/10.1002/agj2.21737.
Pedrosa, V.M., Izidoro, M., Paythosh, S., Dungan, R.S., Olsen, N., Spear, R., de Almeida Teixeira, G.H. 2025. The relationship between respiration rate and quality parameters of russet potatoes during long-term storage. American Journal of Potato Research. 102:93-105. https://doi.org/10.1007/s12230-025-09977-7.
Dreyfus, G., Buck, H., Cadillo-Quiroz, H., Converse, B.A., Hasan, F., Jackson, R.B., Jinnah, S., Jones, C.W., Leytem, A.B., McKone, T., Pang, S.H., Santiesteban, J.G., Stein, L.Y., Turner, A., Walter Anthony, K., Wooldridge, M. 2024. A research agenda toward atmospheric methane removal. Washington, D.C.: The National Academies Press. 284 p. https://doi.org/10.17226/27157.
Rogers, C.W., Spackman, J.A., Tarkalson, D.D., Hu, G., Marshall, J.M., Adeyemi, O., Evans, C.P. 2025. Irrigated spring hull-less food barley response to nitrogen fertilization. Soil Science Society of America Journal. 89(2). Article e70029. https://doi.org/10.1002/saj2.70029.
King, B.A., Rogers, C.W., Tarkalson, D.D., Bjorneberg, D.L. 2024. Malt barley yield and quality response to crop water stress index. Agronomy Journal. 14(12). Article 2897. https://doi.org/10.3390/agronomy14122897.
Rogers, C.W., Adams, C.B., Marshall, J.M., Thurgood, G., Dari, B., Loomis, G. 2025. Barley grain and total biomass mineral nutrient concentrations, uptake, and partitioning. Journal of Plant Nutrition. 48(20):3722-3733. https://doi.org/10.1080/01904167.2025.2522248.
Adams, C.B., Rogers, C.W., Marshall, J., Walsh, O., Thurgood, G., Dari, B., Loomis, G. 2025. Wheat mineral nutrient uptake, harvest indices, and grain density from a regional perspective. Agronomy Journal. 117(3). Article e070066. https://doi.org/10.1002/agj2.70066.
Tarkalson, D.D., Olsen, D., Bjorneberg, D.L., Rogers, C.W. 2025. The case for static range nitrogen management in Idaho sugarbeet production. Soil Science Society of America Journal. 89(1). Article e270025. https://doi.org/10.1002/saj2.70025.