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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

2019 Annual Report

Objective 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. - Sub-objective 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. - Sub-objective 1B: Determine whether uniformity of protein levels in the crop can be achieved with the precision N replacement approach. - Sub-objective 1C: Adapt instruments and algorithms to support on-farm implementation of the N replacement approach to precision fertilizer management in dryland wheat production systems. - Sub-objective 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. Objective 2: Identify whether soil microbial communities adapted to dry environments benefit plant fitness under water limited conditions. - Sub-objective 2A: Identify the composition of microbial consortia naturally adapted to low water availability. - Sub-objective 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. Objective 3. Develop resilient cropping systems and strategies that increase resilience, improve economic returns, and enhance ecosystem services (C1, PS1a); assess their economic and environmental performance of various cropping systems in concert with their supporting components (C2, PS2a; C3, PS3b); and develop decision support systems for optimizing agronomic production in these cropping systems (C2, PS2c). Objective 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 (C3, PS3a).

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. Impact of water availability will be confounded by soil properties; therefore, we may use a microbial transfer experiment where soil inoculum is harvested from different precipitation zones and plants grown at two watering regimes. 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.

Progress Report
This report documents progress for new project 2074-12210-001-00D, which started in September 2018 and replaces expired project 2074-21610-002-00D, "Cultural Practices and Cropping Systems for Economically Viable and Environmentally Sound Oilseed Production in Dryland of Columbia Plateau." In Sub-objective 1A, land off-station was unavailable in time to start the nitrogen-cultivar trial in fall 2018 because of the unexpected loss of the long-term lease. However, firm term leases with other landowners were established for the study to begin in fall 2019. A significant portion of this study had been established on-station in 2017 within the intermediate precipitation zone. Two years of field sampling have been completed. Parameters were measured in four cultivars of winter wheat including grain yield, protein, harvest index, and harvest nitrogen (N) index. Gas samples of nitrous oxide (N2O) were collected weekly during the growing season in selected plots of the study. Samples were analyzed in the laboratory with gas chromatography. Specialized chambers, consisting of a cylinder inserted into the soil and connected with a chamber containing a sponge soaked in acid acting as a gas trap, were used to monitor ammonia (NH3) volatilization. The potassium bromide (KBr) tracer method to monitor nitrate movement below the root zone was abandoned after the labor of sample preparation, KBr extraction, and laboratory analysis proved excessive. Instead, nitrate (NO3) movement was monitored in soil cores extracted from below the root zone at the start and end of each growing season. In Sub-objective 1C, significant progress was made to adapt an affordable spectrometer for use on a combine harvester. The subject spectrometer was modified at the factory to output the detector temperature. Thermal stability of the detector was achieved by putting the instrument inside an insulated enclosure in contact with an inexpensive thermal-electric plate. Fifty grain samples of winter wheat having a wide range in protein concentration were used to calibrate the instrument. A final model, constructed by fitting the spectra of these samples to reference protein values, predicted the protein concentration to within 0.5 percent. Effects of auger speed and sensor orientation on stability of the instrument’s calculated protein values were tested by mounting the instrument to an auger. Predicted protein values were consistent with reference values. Significant deviation occurred only when auger speed was low, suggesting that instrument readings depend on rate of grain flow. Three years of field testing have been completed. A manuscript reporting the project results is in preparation. Also, under Sub-objective 1C, significant progress was made to develop an easy-to-use software for data editing and mapping of on-combine yield and protein data. Collaborators met in Columbia, Missouri, to plan the software design. Algorithms and methods were exchanged to support this effort. A prototype module was constructed for translating protein data for import into the Yield Editor 2.0 software. Under Sub-objective 1D, land was unavailable to initiate the experiment in fall 2018 because of the unexpected loss of the long-term lease and the requirements to work on University ground on-station. Progress has been made by establishing leases and developing treatment maps to initiate the experiment in the fall 2019. In Objective 2, progress was made in developing methods to transfer the soil microbiome as an inoculant. A preliminary experiment demonstrated that the autoclaved soil was not appropriate as a “sterile” medium due to increased levels of available nitrogen and high rates of enzyme activity following a recovery period. Other media such as sterile potting soil or sand will be evaluated.

1. Reduced tillage and crop intensification help control downy brome in dryland winter wheat. Downy brome is a grassy weed that is difficult to control in low rainfall areas of the inland Pacific Northwest where winter wheat is often grown in a two-year rotation with summer fallow involving frequent tillage. ARS scientists and their Oregon State University colleagues in Pendleton, Oregon, investigated the effects of tillage intensity and cropping intensification on infestations of downy brome. Downy brome cover was lower and winter wheat yield was higher when tillage was reduced to a few operations. In addition, downy brome cover was lower when the two-year rotation was intensified to three-year rotations of fallow/winter wheat/spring barley or fallow/winter wheat/spring mustard. Winter wheat yield in the three-year rotation with spring barley was higher than that in fallow/winter wheat, even though weeds were more competitive in the former. Growers could control downy brome in winter wheat by reducing tillage to suppress weed seedling emergence and growth or introducing a spring crop to increase weed competition.

2. Short-term intensified tillage does not have a strong or consistent impact on the soil biology or chemistry in dryland wheat-fallow cropping under low annual precipitation. ARS scientists and an Oregon State University colleague in Pendleton, Oregon, evaluated soils managed under conventional (intensive) and minimum (conservation or sweep) tillage for differences in soil chemistry (pH, inorganic nitrogen, phosphorous, total carbon and nitrogen) and soil biology (bacterial and fungal abundance, and nutrient cycling enzyme activity related to carbon, nitrogen and phosphorous availability). Sampling phase (wheat or fallow), year and soil depth were greater factors influencing soil chemistry, biology, and activity than tillage intensity. Soil chemical and microbial properties were similar between the tillage regimes, but the amount of fungi declined in the wheat phase under conventional tillage. Producers interested in short-term intensified tillage, such as to control weeds, can expect no detriment to microbial nutrient cycling; however, the amount of soil fungi that are important to soil structure may be reduced after the cropped phase.

Review Publications
Schlatter, D.C., Reardon, C.L., Maynard-Johnson, J.L., Brooks, E., Kahl, K.B., Norby, J., Huggins, D.R., Paulitz, T.C. 2019. Mining the drilosphere: bacterial communities and denitrifier abundance in a no-till wheat cropping system. Frontiers in Microbiology. 10:1339.
Gesch, R.W., Long, D.S., Palmquist, D.E., Allen, B.L., Archer, D.W., Brown, J., Davis, J.B., Hatfield, J.L., Jabro, J.D., Kiniry, J.R., Vigil, M.F., Oblath, E.A., Isbell, T. 2019. Agronomic performance of Brassicaceae oilseeds in multiple environments across the Western USA. BioEnergy Research. 12(3):509-523.
Reardon, C.L., Wuest, S.B., Melle, C.J., Klein, A.M., Williams, J.D., McCallum, J.D., Barroso, J., Long, D.S. 2019. Soil microbial and chemical properties of a minimum and conventionally-tilled wheat-fallow system. Soil Science Society of America Journal. 83(4):1100-1110.
San Martin, C., Long, D.S., Gourlie, J., Barroso, J. 2018. Weed responses to fallow management in Pacific Northwest dryland cropping systems. PLoS One. 13(9):1-17.
Barth, V.P., Reardon, C.L., Coffey, T., Klein, A.M., McFarland, C., Huggins, D.R., Sullivan, T.S. 2018. Stratification of soil chemical and microbial properties under no-till management after lime amendment. Applied Soil Ecology. 130:169-177.
Long, D.S. 2018. Site-specific nutrient management systems. In: Stafford, J., editor. Precision Agriculture for Sustainability. Cambridge, UK: Burleigh Dodds Science Publishing. p. 115-125.
San Martin, C., Long, D.S., Gourlie, J., Barroso, J. 2019. Spring crops in three year rotations reduce weed pressure in winter wheat. Field Crops Research. 233:12-20.