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.
This report documents progress for project 2074-11120-004-00D, which started in October 2016 and continues research from Project 2074-11120-003-00D, "Improved Soil Management Practices for Tilled Summer Fallow in the Pacific Northwest." Progress was made on all objectives. Under Objective 1, soil samples were obtained for measurement of soil water and soil organic matter in three long-term experimental sites comparing reduced tillage and zero tillage. Tillage treatments were designed and implemented to optimize reduced tillage for improved water storage with less soil erosion. Under Objective 2, soil gas emission samples were collected and analyzed weekly during the growing season (October through July) in an effort to develop management practices to increase soil organic matter. The crops were harvested and wheat grain and straw samples are being processed. Using the prediction model, basic site-specific data were prepared for ARS GRACEnet sites in Maryland, Pennsylvania, and Minnesota. Simulation results were shared with scientists at these sites. Under Objective 3, soil sampling and chemical analysis toward determining water flux through the soil profile and the potential for nitrogen (N) loss in current and proposed cropping systems was completed to determine appropriate levels of tracer application. A method was designed and constructed for application, and the first round of tracer was applied. For 15N tracer work, incremental background soil samples were collected in the fall and are currently being analyzed in the lab. The plant and straw samples have been collected. The first season's final soil samples have been collected.
1. Management practice to increase deep soil organic carbon. Intensive tillage, low biomass inputs, fallow, and straw burning in the past decades have greatly decreased soil organic carbon in the Pacific Northwest dryland production region. Crop productivity and soil health requires that soil organic carbon is maintained or increased. ARS researchers in Pendleton, Oregon, used producers' fields to measure soil carbon to 60 inch depth during the early 1980s and again in the early 2000s. Winter wheat with peas increased deep soil organic carbon the most, followed by the conservation reserve program and winter wheat with reduced tillage. These results will encourage the development and adoption of deep-rooted legumes, such as peas in the rotation, reducing tillage and reducing fallow for sustainable wheat production.
2. Wheat yields and soil water improve under no-tillage practices. Farmers in the inland Pacific Northwest have doubted whether knowledge gained from small plot experiments can be transferred to farm fields, and whether no-tillage provides sufficient soil water for autumn planting of winter wheat. ARS researchers at Pendleton, Oregon, compared soil water content and winter wheat yields between traditional inversion tillage and current no-tillage technology in two upland drainages in the 12- to 14-inch rainfall region. They found winter wheat yields to be similar between no-tillage and conventional tillage, and there was significantly more plant available water in topsoil before planting under no-tillage than traditional tillage. These results confirmed that improvements in herbicides, equipment, and wheat varieties in the last 30 years have resolved earlier plant-water problems in no-tillage practices and demonstrate that the soil-conserving practice of no-tillage is capable of meeting or exceeding crop productivity from traditional inversion tillage. This work will increase adoption and development of no-tillage cropping systems in the inland Pacific Northwest.
Williams, J.D., Robertson, D.S. 2016. Soil water in small drainages farmed with no-tillage and inversion tillage in northeastern Oregon. Journal of Soil and Water Conservation. 71(6):503-511.
Gollany, H.T., Elnaggar, A.A. 2017. Simulating soil organic carbon changes across toposequences under dryland agriculture using CQESTR. Ecological Modelling. 355:97-104.