Location: Columbia Plateau Conservation Research Center
2025 Annual Report
Objectives
Objective 1: Quantify impact of intercropped legume cover crops with winter wheat to increase soil carbon and reduce herbicide and synthetic nitrogen (N) fertilizer inputs.
Sub-objective 1.A: Identify the best performing legume cover crops for intercropping with winter wheat that reduces herbicide and synthetic N while improving precipitation use efficiency in intermediate rainfall zones.
Subobjective 1.B: Examine whether legume cover crop intercropped with winter wheat can increase soil organic carbon (SOC), reduce herbicide and synthetic N fertilizer inputs, and reduce CO2 and CH4 emissions.
Objective 2: Measure deep root-zone water dynamics in dryland cropping systems to optimize water storage with tillage, crop residue, cover crop, and weed management.
Objective 3: Examine the use of biostimulants and biochar (such as thermal carbonized manure) as amendments in dryland wheat production systems in order to improve soil and plant health, profitability, and resilience to extreme weather and climate change.
Sub-objective 3.A: Establish whether the addition of biostimulants to soils can enhance plant growth and soil properties to reduce drought stress under semi-arid dryland wheat production conditions.
Sub-objective 3.B: Determine whether the addition of thermal carbonized manure to soils can increase soil pH in the N fertilizer application zone and enhance plant nutrient uptake under semiarid dryland wheat production systems.
Approach
1.A. Establish intercropped wheat with 4-legumes. Determine grain yields and wheat, legume, and weed biomasses. Apply herbicides while control subplots are covered to count weeds per species. Collect soil samples at the start of the experiment and after the 4th growing season. Determine total, organic and inorganic C, and N; and extractable P, NO3-N, and NH4-N. Collect soil samples for in-season N fertilization and determine dissolved and labile C and N at the time of N fertilization and at harvest. Monitor soil temperature and water. Collect CO2, N2O, and CH4 samples for two years. Perform life cycle analysis (LCA) from greenhouse gas (GHG) emissions from (1) diesel combustion at each stage of crop production, delivery of seed, fertilizers, pesticides, and (2) direct field emission of GHG.
1.B. Measurements are made in 1) wheat-fallow under reduced tillage, 2) no-till annual winter wheat, and 3) no-till wheat–wheat–sorghum/sudangrass. Half of the plots are planted and managed using herbicide. The other plots are intercropped with a legume. Monitor solar radiation with Albedometers. Collect soil samples and determine total and labile C and N as in 1.A. Soil temperature, water and GHG will be monitored, and the LCA will be performed as in 1.A.
2. Install soil water sensors below tillage depth in controlled experiments on post-harvest weed control, alternative crops, cover crops, and in farmer’s fields of selected management practices. Install sensors in 5-cm boreholes to monitor the root zone and below the root zone to detect upward and downward water movement. A minimum of 24 profiles under commercial farm practices in different locations are monitored for the soil and yield response to precipitation events, weed growth, and cropping patterns. Soil water storage, water extraction by the crop, and yield are principal measurements. The data is posted online in real-time.
3.A. Plots of no-till continuous wheat-wheat with 3-N fertilizer rates (0, 50, 100 kg N/ha) will be used. Apply biostimulants to 4 subplots within the N main plots at a rate of 3.7 L/ha at the 4th leaf growth stage. Grain, biomass yields, and harvest index are determined. Shoots and roots are sampled at V6 & maturity and stored (- 80°C) until analyzed. The samples are extracted and analyzed for up to 18 endogenous plant hormones, 8-carbohydrate and 11 phenol monomers. Carbohydrate monomers are hydrolyzed by H2SO4, separated by anion chromatography, and detected by pulsed amperometry. Phenol monomers are extracted by CuO oxidation and NaOH hydrolysis and detected by GC. Amino acid monomers are extracted, separated by anion chromatography and detected by pulsed amperometry.
3.B. Poultry litter will be pyrolyzed and compared with conifer wood and wheat straw biochars and replicated plots will be treated with each of the 3 biochars and incorporated by rotary tillage. Soil cores will be collected before and after application of the biochar. Total soil N, S, and C, extractable NO3 and NH4, micro- and macronutrients, soil pH, and EC are determined. Winter wheat will be seeded by hand for 3 yrs. Micro- and macronutrients in the wheat grain and straw will be determined at harvest.
Progress Report
This report documents progress for project 2074-11120-005-000D, titled, “Nutrient Cycling and Precipitation Use Efficiency for Increasing Productivity and Resilience in Dryland Agroecosystems ", which started October 2021.
In support of Sub-objective 1.A, weed infestation was evaluated by counting weed species in ½ x 1 m2 frames in each of the intercropped treatments, and third season wheat and residue yields were determined. Daily weather, soil water and temperature data collections will continue until the next growing season. This work supports the development of fundamental knowledge of and practices for soil-based management that contribute to greater agricultural productivity while reducing reliance on inputs, resilience to disturbances, and providing ecosystem services.
In support of Sub-objective 1.B, samples of dissolved and labile carbon and nitrogen in the top 15 cm (~ 6”) soil were determined, 164 carbon and nitrogen flux samples were collected from wheat and wheat-pea intercropped plots and analyzed weekly during the winter wheat growing season (October- July). Monthly collection from August to September will continue, including surface soil temperature and soil moisture measurements. This work contributes to quantifying driving factors in soil carbon cycling, including organic matter dynamics, carbon sequestration, and carbon and nitrogen fluxes and dynamics.
In support of Objective 2, soil water samples have been collected again this year in a winter pea phenology study to compare water use by winter pea versus winter wheat, as well as comparing several new food-grade winter pea varieties. The cover crop trial is now in a second year, and periodic soil samples are being used to measure water use by the different cover crops compared to summer fallow. Installation of gopher-proof cable was completed in five farm fields with two electronic moisture sensor soil profiles in each field. Water use by major herbicide-resistant weeds (Russian thistle and kochia) was measured to determine the return-on-investment for different weed control strategies. This research contributes to the development of cropping systems that promote maximum profits and soil conservation in low rainfall regions.
In support of Sub-objective 3.A, crop yields were collected from the 12 Biostimulants plots. Samples (shoots and roots) during the growing season (at the Vegetation 6 stage) were taken from the middle four rows of each plot leaving two rows on either side as border rows and immediately placed in a deep freezer (- 80°C). This research contributes to advancing our understanding of innovative, non-traditional soil amendment research, including biostimulants, to develop cropping systems that enhance agroecosystems and promote resilience to droughts.
In support of Sub-objective 3.B, soil sample analysis continued to determine pH, nutrient, carbon and nitrogen. This contributes to advancing our understanding of nontraditional soil amendments that improve soil pH and plant nutrient availability which enhance agroecosystems productivity.
Accomplishments
1. More consistent measurement of soil organic matter. Soil organic matter is vital to productive soils, therefore accurately measuring soil organic matter under different management techniques is important to maintain future productivity. An ARS scientist at Pendleton, Oregon, has tested and demonstrated how soil depth measurements are highly influenced by the surface soil density on the day of sampling. This makes it very difficult to get repeatable measurements. Changing our measurement from a linear depth from the soil surface to a mass per area of soil from the current surface, the density problem disappears. Taking intact cores and drying them before measuring the desired soil “mass depth” provides a very simple and practical method for consistent soil measurements. This greater consistency should promote more accurate assessments of which soil amendments might be needed.
2. Cover crops and fumigation are shown to increase soil microbial biomass in potato fields. Soil fumigation is commonly used for pest control in potato production, although it can unintentionally harm non-target organisms in the soil. However, the limited information regarding the combined impact of soil fumigation and cover crops (radish, pea + fava bean, wheat, and mustard) on soil health in potato fields makes it difficult to make appropriate management decisions. An ARS scientist in Pendleton, Oregon, along with Oregon State University, Virginia State University, and Butte College faculty have demonstrated the potential of cover crops to enhance microbial biomass carbon (MBC) compared to the fields without cover crops. Fumigation increased potato tuber yield by 28% in 0.38-0.62 lb. size range. The presence of cover crops can significantly influence the abundance and composition of microorganisms which are indicators of soil health and sustainable agricultural systems for potato production. This will benefit growers and consumers of potatoes.
3. Microbial community composition is shown to respond to differences in soil management practices. Soil microbial communities can be valuable indicators of soil health, or the capacity of soil to provide essential functions that benefit crop production and sustainable agricultural systems. ARS scientists from 15 locations across the United States collaborated and provided soils from different management systems representing a wide range of climate and soil properties. They examined the soil microbial communities which are sensitive to management practices and can help producers understand how their decisions are affecting soil health and drive productivity and sustainability of agricultural lands. Site-specific characteristics were found to have a strong influence on microbial communities. Markers for fungi were more sensitive to management than markers for bacteria, which implies management can affect microbial community composition. Conservation management practices such as reduced tillage, reduced fallow period with cover cropping, and manure applications across dryland regions and nationally are found to be important management practices for developing healthy soils and sustainable crop production systems. The findings can guide local growers and nationally to develop management practices to optimize soil health and sustainable crop production.
4. Land use/cover change and slope gradient impact soil organic carbon stock. Land use and land cover (LULC) could affect soil physicochemical properties, particularly soil organic carbon (SOC) stock. However, the impact varies depending on the physical conditions of a given region or watershed. An ARS researcher in Pendleton, Oregon, along with collaborators at the University of Nebraska and Haramaya University used the Anjeni watershed, which is a highly populated and intensively cultivated area in Northwest Ethiopia, to quantify the impact of LULC and slope gradient on SOC stock and carbon sequestration rate. Soil samples were selected systematically to match the historical records for SOC stock comparison. Four land use types were quantified using Landsat imagery analysis. The result indicated that LULC changes and slope gradient had a major impact on SOC stock and carbon sequestration rate over 30 years in a highly populated watershed. Plantation forests had a significantly higher SOC than cultivated land, and gentle slopes had higher SOC than steep slopes, and the highest SOC stock and SOC sequestration rate were recorded when cultivated land was converted to grassland. A carefully planned land use that involves the conversion of cultivated land to grassland could lead to an increase in soil carbon sequestration and contribute to reducing the carbon footprint of agri-food systems.
Review Publications
Torabian, S., Kim, E., Qin, R., Sathuvalli, V., Gollany, H.T., Kleber, M. 2024. Soil microbial biomass influenced by cover crop after fumigation of potato fields. Science of the Total Environment. 958. Article 177910. https://doi.org/10.1016/j.scitotenv.2024.177910.
Roper III, W.R., Acosta Martinez, V., Veum, K.S., Burgess, C.J., Moore, J.M., Manter, D.K., Stewart, C.E., Emmett, B.D., Liebig, M.A., Fischel, M.H., Lehman, R.M., Franco Jr, J.G., Johnson, J.M., Weyers, S.L., Mikha, M.M., Trippe, K.M., Maul, J.E., Dungan, R.S., Gollany, H.T., Ducey, T.F., Hale, L.E., Jin, V.L., Cavadini, J., Reardon, C.L. 2025. Unraveling edaphic, environmental, and management drivers of soil microbial communities via ester-linked fatty acid methyl esters using a multilocation agroecosystem study. Geoderma. 453. Article 117158. https://doi.org/10.1016/j.geoderma.2024.117158.
Geremew, B., Tadesse, T., Bedadi, B., Gollany, H.T., Tesfaye, K., Aschalew, A. 2023. Impact of land use/cover change and slope gradient on soil organic carbon stock in Anjeni watershed, Northwest Ethiopia. Environmental Monitoring and Assessment. 195. Article 971. https://doi.org/10.1007/s10661-023-11537-7.
Oreja, F.H., Gonzalez-Andujar, J.L., Wuest, S.B., Barroso, J. 2024. Predictive emergence model of russian thistle (Salsola tragus). Científica: Revista de Ciências Agrárias. 47(1):360-364. https://doi.org/10.19084/rca.35131.
Wuest, S.B. 2025. Measuring soil carbon stocks with greater simplicity, accuracy, and repeatability. Soil Science Society of America Journal. 89(1). Article e70012. https://doi.org/10.1002/saj2.70012.