Objective 1: Develop and deliver reduced- or zero-tillage management practices to maintain surface residues and improve water use efficiency that are adapted to specific low-precipitation dryland wheat growing regions and soils. • Subobjective 1A: Determine if differences in surface soil water and organic matter between no-till wheat–fallow and minimum tillage wheat–fallow are likely to produce a long-term advantage for one system over the other. • Subobjective 1B: Test the effect of delayed minimum tillage on seed-zone water in a very dry region in order to recommend an optimum timing. Objective 2: Develop management practices to increase soil organic matter and associated C and nutrients, reduce greenhouse gas emissions, reduce soil acidification, and maximize long-term soil productivity. • Subobjective 2A: Measure soil organic C and soil organic N stock changes, and carbon dioxide, nitrous oxide and methane fluxes to determine the C and N footprint for six dryland cropping systems, and render this information useful to growers, industry representatives, and policy makers. • Subobjective 2B: Project soil organic C stocks in diverse agroecosystems after changes in tillage and cropping system using the process-based C model CQESTR and climate data. Objective 3: Determine water flux through the soil profile and the potential for N loss in current and proposed cropping systems to determine how to improve the efficient use of water and N through the wheat-root zone in specific dryland growing regions. • Subobjective 3A: Compare water storage, water use efficiency, and nitrate leaching between various winter wheat–fallow systems in a low-precipitation zone. • Subobjective 3B: Quantify the relationship between applied N and N uptake, use efficiency, and grain yield in long-term experiments to develop and apply this information in determining optimum fertilization rates for dryland, no-till winter wheat production.
Hypothesis 1A: No-till increases rainfall storage compared to minimum tillage, but neither system has an advantage in preserving soil C. Approach 1A: 1) Make comparisons in plots at Moro, OR (started in 2004), Pendleton, OR (2006), and Ritzville, WA, (2002). 2) Collect data for four years. 3) Measure soil water, organic C, and yield components. If yield components indicate insufficient heads per area, we will increase the planting rate. Approach 1B: Initiate fallow tillage at delayed timings. Measure water at seeding, wheat emergence and yield. Weighing lysimeters will characterize evaporation rates and storage of spring rain in untilled and tilled soil. A rainout shelter for the lysimeters, alterations of tillage timing, and extending tillage plots by a year are contingencies if the weather makes conclusions difficult. Hypothesis 2A: Tillage and crop residue affects soil carbon and greenhouse gases. Approach 2A: Measurements are made in: 1) wheat fallow under reduced tillage, 2) no-till annual winter wheat, 3) no till wheat–wheat–sorghum sudangrass, 4) no-till wheat–fallow (0, 45, 90, 135, 180 kg N/ha N rates), 5) no-till wheat–pea (also five N rates), and 6) wheat–fallow under conventional moldboard plow (zero and 135 kg N/ha). Total soil C, N, and S, extractable P, pH, NO3-N, and NH4-N, grain and biomass will be determined annually. Soil temperature and water will be monitored. CO2, N2O, and CH4 samples will be collected. Because climatic factors could affect gas flux measurements and time required to detect low N2O fluxes from some treatments, a third year might be required. Approach 2B: Projections of soil C changes in agroecosystems after changes in tillage and cropping system will be made using CQESTR. Phase I: Long-term soil organic C data from six selected GRACEnet and REAP project sites will be used to develop SOC databases. Phase II: Create site-specific files. Phase III: Generate long-term predictions for change scenarios. Phase IV: Quantify effects of rotation, tillage, fertilization, and climate change for each site. If predictions do not fit the data sets, sensitive parameters will be identified and optimized, or the model’s limitations will be identified. Hypothesis 3A: No-till has improved soil water storage, water use efficiency, and reduced N migration through the root zone. Approach 3A: Treatments are no till and reduced tillage. KBr will be placed in a furrow at planting. Soil samples will be collected every two months for four years. Hypothesis 3B: Management that reduces N losses will reduce fertilizer required for crop yield. Approach 3B: We will use long-term plots in wheat–fallow and in wheat–pea rotations, with five N treatments (0, 45, 90, 135, 180 kg N/ha). Micro-plots (1 m2) in select plots will receive 15N at the start of the experiment. Metal frames will be used as 45-cm deep physical barriers. Total N, extractable NH4-N, and NO3-N, and 15N will be measured in soil samples. Plant samples will be collected inside and outside of the micro-plots area to detect potential lateral movement of 15N.
For Objective 1, monthly collection of soil samples in minimum and no tillage systems continues with only a few winter months missing due to excessive snow and the government shutdown. Soil temperature differences are being measured during sample collection. Laboratory analysis for organic carbon is proceeding as samples arrive from the field. Tillage timing treatments have been implemented in this summer’s fallow plots and wheat is nearly ready for harvest in last year’s summer fallow plots. Samples are being taken monthly in untilled plots to monitor evaporation throughout the growing season. For Objective 2, the third-year of gas samples (carbon dioxide, nitrous oxide, ammonia and methane) were collected and analyzed weekly during the growing season (October-July) except during the Government Shutdown. The second-year’s grain samples are being analyzed for nitrogen to determine the protein concentration. The long-term data from one Resilient Economic Agricultural Practices (REAP) site was utilized in validating the CQESTR model and we determined minimum biomass required to maintain soil organic carbon and published in an invited manuscript. For Objective 3, seasonal soil water sampling continues. Plots with potassium bromide applications were sampled and the samples processed through our in-house laboratory facilities with analysis of the resulting data begun. The second-year soil and plant samples from 15N-labeled-tracer micro-plots are currently being analyzed. The first-year soil and plant samples from 15N-labeled-tracer micro-plots were organized in a spreadsheet.
1. Cropping intensification and soil water storage in the low precipitation Pacific Northwest. When looking for ways to increase soil quality and cropping efficiency, farmers in the inland Pacific Northwest may add new crops to reduce the frequency of fallow. ARS scientists in Pendleton, Oregon, compared a three-year camelina—fallow—winter wheat rotation versus the standard two-year fallow—winter wheat rotation. It was revealed that the spring camelina crop and its normal complement of weeds depleted soil water more than a traditional winter wheat crop. This deficit in deep water storage was not recovered over the following two winters and caused a small but significant reduction in wheat yields. Farmers considering intensified rotations will need to factor in water use and its effect on total profits and the resiliency of their primary cash crop during dry years. This information will help farmers choose the most sustainable rotations.
2. Predicted annual biomass input to maintain soil organic carbon under contrasting management. ARS researchers in Pendleton, Oregon, and Morris, Minnesota, predicted soil organic carbon in western Minnesota, with the CQESTR simulation model. The change in soil carbon has been examined under 1) conventional tillage since 1995, 2) no-tillage since 1995, and 3) no-tillage since 2005. Only no-tillage producing 2.81 tons/acre/year above-ground biomass and no biomass removal was predicted to increase soil organic carbon stocks, at a rate of 0.14 ton of organic carbon/acre/year until 2035. Corn residue is an important source of lignocellulosic feedstocks for meeting U.S. renewable energy goals, but how much residue can be harvested without losing soil carbon? No-tillage has the potential to maintain soil organic carbon at a minimum annual aboveground carbon input of 1.67 tons/acre. Growers should exercise caution in removing above-ground biomass, especially under conventional tillage.
Shiwakotia, S., Zheljazkov, V.D., Gollany, H.T., Kleber, M., Xing, B. 2019. Macronutrients in soil and wheat as affected by a long-term tillage and nitrogen fertilization in winter wheat-fallow rotation. Agronomy. 178(9):1-11. https://doi.org/10.3390/agronomy9040178.
Shiwakotia, S., Zheljazkov, V.D., Gollany, H.T., Xing, B., Kleber, M. 2019. Micronutrient concentrations in soil and wheat decline by long-term tillage and winter wheat-pea rotation. Agronomy. 9(7):359. https://doi.org/10.3390/agronomy9070359.
Gollany, H.T., Nash, P.R., Johnson, J.M., Barbour, N.W. 2020. Predicted annual biomass input to maintain soil organic carbon under contrasting management. Agronomy Journal. 2020:1-14. https://doi.org/10.1002/agj2.20068.
Shiwakotia, S., Zheljazkov, V.D., Gollany, H.T., Xing, B. 2019. Tillage affects macronutrients in soil and wheat of a long-term dryland wheat-pea rotation. Soil and Tillage Research. 190:194-201. https://doi.org/10.1016/j.still.2019.02.004.
Ankathi, S.K., Long, D.S., Gollany, H.T., Prajesh, P., Shonnard, D. 2018. Life cycle assessments of oilseed crops produced in rotation with dryland cereals in the inland Pacific Northwest. International Journal of Life Cycle Assessment. 24(4):627-641. https://doi.org/10.1007/s11367-018-1488-y.
Lutcher, L.K., Wuest, S.B., Johlke, T.R. 2019. First leaf emergence force of three deep-planted winter wheat cultivars. Crop Science. 59(2):772-777. https://doi.org/10.2135/cropsci2018.08.0495.
Dell, C.J., Gollany, H.T., Adler, P.R., Skinner, H., Polumsky, R.W. 2018. Implications of observed and simulated soil carbon sequestration for management options in corn-based rotations. Journal of Environmental Quality. 47(4):617-624. https://doi.org/10.2134/jeq2017.07.0298.
Cavigelli, M.A., Nash, P.R., Gollany, H.T., Rasmann, C., Polumsky, R.W., Le, A.N., Conklin, A.E. 2017. Simulated soil organic carbon changes in Maryland are affected by tillage, climate change, and crop yield. Journal of Environmental Quality. 47(4):588-595. https://doi.org/10.2134/jeq2017.07.0291.