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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

2021 Annual Report

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.

Progress Report
Following the unexpected loss of a land lease, suitable land was found and leased for field experiments in the high and low rainfall sites. Under Sub-objective 1B, we made significant progress toward determining how fertilizer rate and plant cultivar influence the microbial supply of nitrogen (N) to the soil. The microbial component was expanded from analyzing only in-crop to both fallow and cropped soils. Ammonia oxidation assays are complete for all samples, and substantial progress has been made for amidase. We adapted methods for the soil analyses to small-volume microplate assays and optimized the protocols for the use of automated liquid handling robots. We also optimized a robotic-enabled microplate protocol to significantly reduce labor and hazardous waste generation by coupling the measurement of soil inorganic nitrogen (nitrate/ammonium) to mineralization assays. Analysis of microbial activity data will inform the selection of nitrogen and cultivar treatments in Objective 2. Additionally, progress has been made in planning for the initiation of the first nitrogen replacement trial by quantifying the grain N removed from the first-year cultivar-fertility trial. Field research of Sub-objective 1B has been completed in determining fertilizer use efficiency with attention to nitrogen losses due to volatilization and leaching. Three years of data were compiled for grain yield, grain protein concentration, harvest index, nitrate leaching, and nitrous oxide, and ammonia emission. Progress is underway for Sub-objective 1C, with plans to hold a virtual training in August 2021 on the Yield Editor software. Challenges in cost and travel were overcome by hosting a virtual rather than in-person meeting. The training will target growers interested in computing tools that make use of grain yield and protein maps to create fertilizer application plans. Significant progress on the residue height trial of Sub-objective 1D was made at both low and high precipitation regions. Continuous near-surface, inter-row measurements were made with ultrasonic anemometers and combined temperature-humidity sensors were installed at the site. Additionally, low-cost, self-logging soil temperature arrays were constructed and installed in the inter-row soils to monitor potential differences in temperature due to shading and wind flux. Challenges associated with frequent travel to the remote sites for manual data collection were overcome by telemetry using instruments with onboard data logging and Bluetooth data collection. Game cameras and graduated staff gauges enabled the visualization and measurement of snow capture at remote sites, including an accurate collection of hourly snowfall data for one of the largest snowfall events in the last 20 years. Under Sub-objective 2A, progress was made in the collection and archiving of soils for DNA analysis. The challenge in the timing between treatment selection (based on Sub-objective 1B) and rhizosphere collection was overcome by collecting and archiving the "root-impacted" soil from all cultivars at three nitrogen rates and two precipitation regions. The advantages of root-impacted soil compared to the rhizosphere are 1) the ability to directly compare measurements of microbial composition, activity, and soil chemistry due to the larger soil volume and 2) numerous samples can be collected and composited across an experimental plot with minimal impact to yield measurements. Progress was made under Sub-objective 2B with a preliminary "microbial-transfer" experiment to develop methods for soil sterilization and inoculum, water regimes, and biomass assessments. A protocol to measure plant proline content as an indicator of plant drought stress was optimized for wheat. Additionally, progress was made to improve the efficiency of quantitative polymerase chain reaction (PCR) analysis used to assess the abundance of functional genes related to carbon and nitrogen cycling. The microbial-transfer experiments will be initiated upon selection of treatments indicated by Sub-objective 1B. Significant progress has been made under Objectives 3 and 4 on developing alternative and cover crop systems in the low and intermediate precipitation regions. The two trials were conducted by Oregon State University colleagues funded through a non-assistance cooperative agreement. The weed challenges encountered in the first-year trial were partially overcome with more aggressive and frequent control practices. Fall-seeded lentil and winter pea varieties from commercial and the ARS breeding program in Pullman, Washington, continued to show positive results for emergence and weed competition. Plant tissues from the legumes in the first-year trial have been analyzed for nitrogen-15 isotope content and will inform scientists whether legumes uptake nitrogen differently in the two rainfall zones.

1. Automated detection of yellow flowering in canola. Monitoring the growth and development of crops is important for making crop management decisions on crop protection and fertilization. ARS scientists in Pendleton, Oregon, monitored the onset and duration of flowering of canola using a sequence of aerial images that were taken over the growing season. At the same time, the crop was characterized for changes in above-ground biomass, timing of flowering, and timing of flower shedding. A computer algorithm was developed that uses spectral indices sensitive to the amount of green biomass and the presence of yellow flowers. Contrasts between these two indices were successfully used to estimate the onset and duration of flowering. Changes between vegetative and reproductive development can be automatically detected, enabling the application of this technology for satellite- or aircraft-based detection of flowering within and between farm fields. Such information might be integrated with agrometeorological data to assess disease risk and yield prediction.

2. Value of weed maps for on-farm management. Weeds that go to seed late in the season need to be controlled before they re-infest the next crop. Oregon State University and ARS researchers in Pendleton, Oregon, used weed maps and yield monitor data to evaluate the effectiveness of crop rotations and weed control strategies over four consecutive years in a commercial wheat field. Weed and yield maps showed similar distributions indicating that much of the crop variation was associated with weed competition. Potential savings using weed maps for spot herbicide application varied from 10 to 95%. Weed maps at harvest are useful for explaining crop yield variability and directing spot spraying of weeds after harvest. Growers might implement mapping of green weeds on a combine using optical sensors that can detect chlorophyll entering the grain bin.

Review Publications
Long, D.S., Griffith, D.A., Kvien, C.V., Clay, D.E. 2021. Moran eigenvector filtering of multi-year yield data with application to zone development. Agronomy Journal. 4(1). Article e201404.
Sulik, J.J., Long, D.S. 2020. Automated detection of phenological transitions for yellow flowering plants such as brassica oilseeds. Agrosystems, Geosciences & Environment. 3(1). Article e20225.
Chatterjee, A., De Jesus, A.F., Goyal, D., Sigdel, S., Cihacek, L.J., Farmaha, B., Jagadamma, S., Sharma, L., Long, D.S. 2020. Temperature sensitivity of nitrogen dynamics of agricultural soils of the United States. Open Journal of Soil Science. 10(7):298-305.
Trippe, K.M., Manning, V., Reardon, C.L., Klein, A.M., Weidman, C.S., Ducey, T.F., Novak, J.M., Watts, D.W., Rushmiller, H.C., Spokas, K.A., Ippolito, J.A., Johnson, M.G. 2021. Phytostabilization of acidic mine tailings with biochar, biosolids, lime, and locally-sourced microbial inoculum: Do amendment mixtures influence plant growth, tailing chemistry, and microbial composition? Applied Soil Ecology. 165. Article 103962.
Barroso, J., San Martin, C., McCallum, J.D., Long, D.S. 2021. Economic and management value of weed maps at harvest in semi-arid cropping systems of the US Pacific Northwest. Precision Agriculture.
Wuest, S.B., Reardon, C.L. 2021. Electrostatic method to remove particulate organic matter from soil. The Journal of Visualized Experiments (JoVE). 168. Article e61915.
Yan, Z., Collins, H.P., Machado, S., Long, D.S. 2021. Residue management changes soil phosphorus availability in a long-term wheat-fallow rotation in the Pacific Northwest. Nutrient Cycling in Agroecosystems. 120(1):69-81.
Williams, J.D., Reardon, C.L., Wuest, S.B., Long, D.S. 2020. Soil water infiltration after oilseed crop introduction into a Pacific Northwest winter wheat-fallow rotation. Journal of Soil and Water Conservation. 75(6):739-745.