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Research Project: Attaining High Quality Soft White Winter Wheat through Optimal Management of Nitrogen, Residue and Soil Microbes

Location: Columbia Plateau Conservation Research Center

Project Number: 2074-12210-001-000-D
Project Type: In-House Appropriated

Start Date: Sep 6, 2018
End Date: Sep 5, 2023

Obj. 1: Extend the N replacement approach to soft white winter wheat for guiding precision management of fertilizer N and crop residue to optimize soil microbial processes and maximize the biological potential of soil. 1A: Evaluate grain protein concentration and yield response to N under varying levels of water to define the critical protein level and fertilizer N equivalent to a unit change in protein for popular cultivars of soft white winter wheat. 1B: Determine whether uniformity of protein levels in the crop can be achieved with the precision N replacement approach. 1C: Adapt instruments and algorithms to support on-farm implementation of the N replacement approach to precision fertilizer management in dryland wheat production systems. 1D: Evaluate the effects of residue management (standing, distributed on the soil surface, or removed) on the plant-available N, precipitation capture efficiency, crop productivity, weed density, and microbial activity during the 13 months of fallow. Obj. 2: Identify whether soil microbial communities adapted to dry environments benefit plant fitness under water limited conditions. 2A: Identify the composition of microbial consortia naturally adapted to low water availability. 2B: Determine whether cultivar selection and N management can be manipulated to shift the structure and function of microbial communities to benefit plants under water stress. Obj. 3. Develop resilient cropping systems and strategies that increase resilience, improve economic returns, and enhance ecosystem services; assess their economic and environmental performance of various cropping systems in concert with their supporting components; and develop decision support systems for optimizing agronomic production in these cropping systems. 3A: Compare economic returns from the variable N replacement approach based on previous season’s site-specific SWW crop yield data and conventional uniform N placement based on field bulk soil sampling and laboratory testing. 3B: Increase dryland farming resilience by developing cropping systems more intensive and diverse than the conventional winter wheat-fallow system. 3C: Investigate the yields and economic returns of alternative crops following winter wheat and winter wheat following cover crops across low and intermediate precipitation zones using current and future climate scenarios. Obj. 4. Increase the sustainability resilience and tolerance of the dryland crop production system to biotic and abiotic stressors through improved understanding of developmental, environmental, and management factors that limit plant health and growth, including but not limited to stress tolerance, water use efficiency, and disease resistance. 4A: Evaluate stress indicators and yield components of wheat in alternative cropping systems compared to wheat-fallow with relation to soil water availability, disease incidence, and rotational crop morphology. 4B: Investigate crop response to water deficit, high temperature, and/or nitrogen availability.

1A: A winter wheat-fallow Cultivar-Fertility Study located at 2 sites in the low and intermediate precipitation zone in Eastern Oregon will include 3 soft white winter wheat cultivars fertilized with inorganic nitrogen (N) at 4 rates. The study will be repeated for 3 years. Yield and grain protein concentration (GPC) measured with near-infrared spectroscopy will define the critical GPC, an indicator of crop N deficiency or adequacy. 1B: A N-Replacement Study will follow 1A in which plots will be split and fertilized based on 1) amount of N needed to achieve target protein based on the critical GPC, and 2) university recommendations based on soil N and potential yield. Select plots will be analyzed for inorganic N, nutrient cycling capacity, microbial community composition, N leaching and gaseous N loss. 1C: The GPC measurements from the relatively inexpensive AvaSpec2048 spectrophotometer will be compared to data from dry combustion. Publicly available software will be adapted from Yield Editor software in collaboration with ARS, Columbia Missouri. 1D: Winter wheat residue in the 2 precipitation zones 1) cut high, left standing, 2) cut high, flattened, 3) cut low, spread, 4) cut low, removed. Measurements include yield, soil/air temperature, air movement, soil water content, inorganic N, and microbial nutrient-cycling activity. 2A: Rhizosphere and bulk soil microbial communities will be characterized from plots replicated in the low and intermediate precipitation zones. Soils will be analyzed for chemistry and enzymes related to carbon and N-cycling, and microbial composition. 2B: Rhizosphere soils collected from different cultivars of 1A at 2 N rates will be analyzed for nutrient cycling activity and communities sequenced from treatments promoting or inhibiting activity. Microbial communities will be evaluated for benefit to wheat in a microbial transfer potting experiment. 3: Economic benefit from replacement N management and intensified cropping systems will be evaluated. An alternative crop trial (AC) and cover crop trial (CC) will be conducted. The winter wheat (WW)-chemical fallow (CF) system will be intensified in a low precipitation (<250 mm) site as a WW-AC-CF rotation and at a high precipitation (<420-mm) site as a WW-AC rotation. The CC trial will be conducted at both sites as WW-cover crop fallow. Each trial will be initiated at a new location for three replicate years. A calibrated model will be provided within a crop simulation platform that will be useful for determining the different alternative crops and cover crops that producers are likely to consider. 4: The plant stress response and yield differences will be evaluated in the alternative and cover crop trials. Soil water availability, disease incidence, soil nutrient cycling, soil chemistry and yield traits will be quantified in each of the trials. Multiple regressions will be used to model the yield and stress variables as a function of the abiotic stressors. Results will identify benefits or detriments of alternative cropping systems to the primary wheat crop in terms of herbicide use, disease incidence, nutrient availability, soil quality, and water availability.