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.
In support of Sub-objective 1A, sample collection continues, including surface temperature measurements at two depths, except for treatments where the soil was extremely dry. The samples have been processed within a few months of collection, except for the most recent samples. Preliminary results have been examined to search for any supplementary data that could be collected toward the end of the experiment. In support of Sub-objective 1B, tillage timing treatments are complete, and the only data remaining to be collected is the yield data for the final year. Soil water data is being analyzed and prepared for publication. In support of Sub-objective 2A, greenhouse gas (carbon dioxide, nitrous oxide, and methane) samples were collected and analyzed weekly during the growing season (October- July), and monthly during August to September. Ammonia emission was measured during active emission periods. The calculation of yearly emissions is progressing. This contributes to the development of management practices to reduce greenhouse gas emissions, increases soil organic matter, associated carbon and nutrients, and maximizes long-term productivity. In support of Sub-objective 2B, the long-term soil organic carbon (SOC) data from one Resilient Economic Agricultural Practices (REAP) site, with climate prediction scenarios for Pennsylvania, was utilized in validating the process-based carbon model (CQESTR) to predict the impact of climate change on SOC and was compared with predicted impact of climate change on SOC at Oregon. These computer simulations contribute to projected SOC stocks change under predicted climate change in diverse agroecosystems. In support of Sub-objective 3B, incremental soil samples were collected from the 15N-labeled-tracer micro-plots and are currently being analyzed. The third-year’s grain samples are also being analyzed for 15N-labeled-tracer. This data contributes to quantification of the relationship between applied nitrogen (N), N uptake, N use efficiency under wheat-fallow and wheat-pea cover crop rotations, and grain yield for dryland no-till winter wheat production.
1. Management practices to reduce the decline in micronutrient concentration in wheat. Impact of tillage and nitrogen (N) application rates on micronutrient content in wheat is limited. An ARS researcher at Pendleton, Oregon, along with an Oregon State University collaborator, compared impacts of long-term sweep tillage, disking, and moldboard plow, and five N rates on the availability of micronutrients in soils and wheat tissues. A greater concentration of soil manganese (Mn) was found under disk than under moldboard plow. Inorganic N application reduced extractable soil copper (Cu), but increased Mn in wheat grain. Comparison of micronutrients with adjacent undisturbed grass pasture revealed that after 75 years of N fertilization and tillage, the wheat-fallow plots lost 43% and 53% of extractable zinc (Zn) and Cu, respectively. Disking and N application could reduce the rate of micronutrient declines in soil and wheat grain over time compared to moldboard plow tillage without N fertilization. However, nitrification-derived acidity must be considered. This information will help farmers choose the most effective tillage and N fertilizer rates to provide proper plant micronutrients to maintain wheat yields and nutritional value while sustaining dryland crop production.
2. Macronutrients in soils and wheat reflect variation in crop residue and fertilizer inputs. Knowledge of the consequences of long-term land management on nutrient status is limited. An ARS researcher at Pendleton, Oregon, along with a collaborator from Oregon State University, used a long-term agroecosystem experiment to examine macronutrient dynamics associated with residue management methods and the type of fertilizer under a dryland winter wheat-fallow rotation. After receiving the same treatments for 84 years, concentrations of soil organic carbon, total nitrogen (N), sulfur, extractable magnesium, potassium (K), and phosphorous (P) in the top four inches of soil significantly increased with the addition of farmyard manure (FYM), compared to synthetic N fertilizer. The N rate of 80 pounds per acre reduced the accumulations of P, K, and calcium in grain compared to the 0 and 40 pounds per acre N applications. The residue incorporation with FYM can play a vital role in reducing the macronutrient decline over time. Growers and their advisors can use this information to guide the development of proper soil fertility practices to improve wheat nutritional value and maintain wheat yields while sustaining dryland wheat production.
3. Organic and inorganic amendment reduced declines in micronutrient concentration in wheat. Information on the effects of various methods of residue management on micronutrients in soil and wheat over time is limited. An ARS researcher at Pendleton, Oregon, along with a collaborator at Oregon State University, used a long-term experiment to determine the impact of synthetic nitrogen (N) fertilizer, farmyard manure (FYM), and crop residue management on micronutrient concentrations in soil and wheat tissue. After 84 years, extractable manganese and boron in the top four inches of soil decreased in all plots, except for boron in farmyard manure and spring-burned residue plots. Extractable zinc (Zn) increased with FYM while it decreased with synthetic N application; however, total Zn in wheat grain increased by 7% with 80 pounds per acre synthetic N compared to FYM application. Wheat growers can integrate synthetic N fertilizer with FYM with the most effective residue management to reduce micronutrient losses from cultivation over time and provide proper plant micronutrients to maintain wheat yields and nutritional value.
4. Impact of tillage timing and intensity on micronutrient concentrations in soil and wheat tissues. Tillage and nitrogen (N) fertilization effect on soil and plant micronutrient dynamics under a dryland winter wheat-spring pea rotation remain uncertain. An ARS researcher at Pendleton, Oregon, along with an Oregon State University collaborator, used archived samples to determine the influence of tillage timing, and intensity (fall tillage, spring tillage, and no-tillage) on soil micronutrient concentrations in soil and winter wheat, and compared soil micronutrient concentrations with a nearby grass pasture. After 52 years of wheat-pea rotation, extractable boron, manganese (Mn), zinc (Zn), copper, and iron in soil were unaffected by tillage methods; however, a significant decline in extractable Zn in the top four inches of soil was observed compared to adjacent undisturbed grass pasture. The no-tillage plots maintained extractable Mn concentration comparable with the grass pasture plot, while fall tillage, and spring tillage plots had lower Mn than grass pasture. The decline in soil pH, and the greater amount of organic matter within the surface soil of no-tillage plots sustained micronutrient availability compared to other tillage methods. This information will help growers and their advisors in selecting proper management and soil fertility practices to improve crop nutritional value while sustaining wheat yields and dryland wheat production.
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