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ARS Home » Pacific West Area » Pullman, Washington » Northwest Sustainable Agroecosystems Research » Research » Research Project #430915

Research Project: Improving Air Quality, Soil Health and Nutrient Use Efficiency to Increase Northwest Agroecosystem Performance

Location: Northwest Sustainable Agroecosystems Research

2021 Annual Report

The overall project goal is to enhance the resilience and sustainability of cropping systems and increase their capacity to deliver multiple agroecosystem services (e.g., healthy, bio-diverse, resilient soil). During the next five years we will focus on the following objectives. Objective 1: Improve agricultural practices to reduce soil erosion, associated particulate emissions, and losses of soil C and essential nutrients. • Subobjective 1A: Conduct life-cycle assessment of wind erosion and associated losses of PM10 and nutrients. • Subobjective 1B: Determine effect of irrigated and dryland management systems on wind erosion and associated emissions of PM10 and nutrients. Objective 2: Develop precision conservation practices to enhance soil health, reduce greenhouse gas emissions, and increase carbon sequestration and nutrient-use efficiencies. • Subobjective 2A: Conduct long-term, site-specific assessment of agroecosystem C, N, and P cycling and flows. • Subobjective 2B: Develop and determine precision evaluation of agroecosystem performance and associated soil health metrics. Objective 3: Develop biological control practices for weed management and enhanced soil biological functions. • Subobjective 3A: Isolate, select, and screen for weed-suppressive bacteria that specifically inhibit annual grass weeds, do not injure crops, native or near native rangeland plants. • Subobjective 3B: Evaluate the survival and efficacy of annual grass weed-suppressive bacteria to reduce annual grass weeds in the field. Objective 4: Develop integrated and economically viable cropping systems that are designed to: adapt to and mitigate climate change, reduce pest infestations, improve soil health, and provide environmental services.

1.a. A life-cycle assessment of wind erosion and associated losses of PM10 and nutrients will be conducted during each phase of a winter wheat – summer fallow rotation. Standard core methods will be implemented in assessing long-term wind erosion as outlined in “Standard Methods for Wind Erosion Research and Model Development.” 1.b. Effects of conventional and conservation crop and tillage systems on wind erosion and associated emissions of PM10 and nutrients will be quantified using a portable wind tunnel under both irrigated and dryland agricultural conditions. 2.a. Landscape scale, spatiotemporal variability of agroecosystem stocks and flows of C, N, and P following conversion from conventional tillage to no-tillage will be assessed at the Long-Term Agroecosystem Research (LTAR) site at the Cook Agronomy Farm. Understanding the long-term impacts of agroecosystems on stocks and flows of major elements is lacking and key to the development of sustainable agricultural systems. 2.b. Characterize spatiotemporal agroecosystem performance (e.g. productivity, nutrient-use efficiencies) and link to soil health metrics. Linking soil health metrics to agroecosystem performance is currently lacking and if achieved will foster a broader and more complete assessment of agricultural systems as well as provide science-based aids to agricultural management decisions. The LTAR site at the Cook Agronomy Farm is the setting for the experiment. 3.a. Isolate, select, and screen for weed-suppressive bacteria that specifically inhibit annual grass weeds, do not injure crops, native or near native rangeland plants. Select soil microorganisms are expected to reduce specific weeds in the field. Studies are a combination of: isolation of soil bacteria, Agar root bioassays, and growth-chamber plant/soil bioassays. 3.b. Evaluate the survival and efficacy of weed-suppressive bacteria to reduce annual grass weeds in the field. Weed-suppressive bacteria are expected to inhibit specific weed species under variable field conditions. Field studies will determine interactive effects among bacteria, herbicides, soil, residue, weed seed bank and non-weed plants on inhibition of annual grass weeds.

Progress Report
For Objective 1, significant progress was made in assessing, modeling and publishing crop rotation, soil amendment and tillage effects on wind erosion, a significant problem of dryland cropping systems in the Inland Pacific Northwest. Here, greater stability of soil aggregates under no-tillage decreases susceptibility to wind erosion; whereas, crop rotation and bio-solid application had relatively minor impacts. Developing cropping systems that maintain annual cover and increase aggregate stability are required to reduce the hazard of wind erosion. Improvements to the wind erosion model were realized that aid prediction of management effects on wind erosion factors. Model simulations using the Wind Erosion Prediction System (WEPS) were used to assess annual dust emissions from wind erosion across the dryland cropping region of the inland Pacific Northwest. Model simulations indicated annual losses of soil and particulate matter (PM10) have decreased across the region. The maximum annual soil loss and PM10 loss of occurred in the Grain-Fallow agroecosystem class where annual fallow is a major land use. In support of Objective 2, research at the Cook Agronomy Farm Long-Term Agroecosystem Research (LTAR) completed analyses to assess management impacts on soil health metrics as well as soil carbon (C), nitrogen (N), and Phosphorus (P) budgets. Considerable research on the soil microbiome discovered linkages to crop yields and relationships to various soil properties such as organic matter, pH and other soil health properties. Long-term incubations to quantify labile soil C pools found significant stocks of labile soil organic C in the subsoil that were sensitive to soil management. Factors such as the disturbance level of various types of no-tillage drills were found to significantly impact the surface storage of soil carbon. Complementary research included monitoring greenhouse gas flux with Eddy co-variance flux towers and in-field lysimeters and flumes for assessing differences in hydrologic cycles and water quality between business-as-usual and aspirational Long-Term Agroecosystem Researh (LTAR) treatments. Soil tests to determine lime requirements for addressing soil acidification in dryland cropping systems of the inland Pacific Northwest were evaluated and published. Dangers of long-term subsoil acidification were discovered and documented to occur at different locations in farm fields. Drivers of deep soil acidification likely include factors such as applied nitrogen fertilizers, water infiltration versus surface run-off, and yearly hydrologic cycles, water consumption, and redistribution that occur at field scales.

1. Hidden dangers of long-term soil acidification quantified. Soil acidification that negatively impacts crop performance is occurring in many agricultural regions of Western states. Primarily driven by applied nitrogen fertilizers, soil acidification was thought to only occur in surface soils. An ARS researcher, however, discovered that soil acidification is occurring at depths of at least 1.5 m in some field locations of the Cook Agronomy Farm Long-Term Agroecosystem Research site. Long-term no-tillage was discovered to ameliorate deep soil acidification while surface soil acidification continued. This research amplifies the need to further explore factors that drive soil acidification at field scales relevant to farmers. Dangers of continued soil acidification are many including increased aluminum toxicity to most crops currently grown.

Review Publications
Pi, H., Huggins, D.R., Sharratt, B.S. 2020. Threshold friction velocities influenced by standing crop residue in the inland Pacific Northwest, USA. Land Degradation and Development. 31(16):2356-2368.
Pi, H., Huggins, D.R., Sharratt, B.S. 2020. Influence of clay amendment on soil physical properties and threshold friction velocity within a disturbed crust cover in the inland Pacific Northwest. Soil and Tillage Research. 202 Article 104569.