Location: Soil and Water Conservation Research
Project Number: 2074-12210-001-00-D
Project Type: In-House Appropriated
Start Date: Sep 6, 2018
End Date: Sep 5, 2023
The long-term objective is to promote adoption of precision nitrogen (N) management in the dryland wheat (Triticum aestivum L.) region of the Pacific Northwest. To encourage adoption, growers need techniques that are designed to work in semiarid environments where water is limiting. Nitrogen management is central to the ongoing issue of input costs that are high relative to low wheat prices. Precision N management promises to improve fertilizer input efficiency and optimize yield while achieving desired grain protein levels for reliable high-quality production. In the Pacific Northwest, over 75% of the dryland acres receive less than 460 millimeters (mm) of annual precipitation. Therefore, most producers (90%) practice a winter wheat – fallow rotation where a crop is produced every two years and a 14-month fallow is used to store soil water for the next wheat crop. The primary focus of the planned research is on the low and intermediate precipitation zones of east-central Washington and north-central Oregon representing the largest rainfed cropping region in the far western U.S. at over 1.5M hectares. During the next five years, we will address the following objectives: 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.
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.