1a. Objectives (from AD-416)
Past and current farming practices in the dryland region of the Pacific Northwest (PNW, northern Idaho, north central Oregon and eastern Washington) have resulted in excessive soil erosion by wind and water, declining soil organic matter levels, poor N use efficiency and losses of biological diversity. These adverse processes are linked to regional degradation of air, water and soil resources and contribute to GHG emissions that drive climate change. This project addresses knowledge gaps associated with the capacity to understand, predict and mitigate PM10/PM2.5 and GHG emissions from dryland agricultural lands. Objective 1. Characterize key environmental and management drivers of agricultural wind-blown dust and PM10/PM2.5 emissions that will improve process-oriented models and decision aids. Sub-objective 1.a. Determine the relationship between soil wetness/crusting and emission of windblown dust and PM10/PM2.5. Sub-objective 1.b. Determine the biotic factors driving aggregate formation and stability in dryland soils and their influence on windblown dust and PM10/PM2.5 emissions. Sub-objective 1.c. Determine the effect of wind erosion and management practices on soil organic matter (SOM), soil biological communities and other soil characteristics. Objective 2. Develop techniques for identifying sources of PM10/PM2.5 to better associate management practices with PM10/PM2.5 emissions and to corroborate models. Sub-objective 2.a. Determine the efficacy of FAME and tracer methods in discerning soils contained in various mixtures. Sub-objective 2.b. Determine point source soil movement and FAME efficacy using known microbial tracers. Sub-objective 2.c. Determine the effectiveness of using FAME fingerprinting to corroborate the Columbia Plateau regional dust transport model. Objective 3. Characterize roles of environmental and management drivers on soil C and N cycling as factors regulating GHG (N2O, CO2) emissions from agricultural soils. Sub-objective 3.a. Determine soil C sequestration rates and CO2 flux as influenced by agroecosystem drivers (e.g. soil, topography, micro-climate, organisms, management). Sub-objective 3.b. Determine biogeochemical dynamics of soil C and N including N2O flux as influenced by agroecosystem drivers (e.g. soil, topography, micro-climate, organisms, management). Objective 4. Develop agricultural PM10/PM2.5 and GHG mitigation strategies and management decision aids for Pacific Northwest cropping systems. Sub-objective 4.a. Determine the effectiveness of alternative tillage and cropping practices in reducing the emission of windblown dust and PM10/PM2.5 from agricultural soils. Sub-objective 4.b. Develop precision N management practices that increase N use efficiency and decrease N2O emissions.
1b. Approach (from AD-416)
1a. Sediment and PM10/PM2.5 flux, will be evaluated as a function of soil water content/matric potential & crust type/cover/thickness for five major soil types using a portable wind tunnel. Crust type & morphology will be ascertained by microscopy & PLFA & FAME analyses. 1b. Soil aggregate properties will be assessed under a range of crop & tillage systems being examined to control wind-blown dust. Soil aggregate size classes from different crop & tillage systems will be analyzed to identify microbial community composition (PLFA & FAME analyses), active SOM, C source & crushing strength. 1c. Long-term cropping system studies at Lind, Pullman, & Ritzville will be used to assess impacts on soil quality over time including bulk density, soil pH, electrical conductivity, organic C & N, aggregate size distribution, N movement & soil microbial constituents. 2a. Ongoing research will fingerprint soils & PM10 material from across the PNW using FAME. 2b. Bacteria & fungi containing natural markers will also be evaluated as tracers that can be retrieved from soils due to their unique traits of antibiotic resistance or strain-specific molecular markers to determine point source soil movement. 2c. The FAME & bacterial tracer studies will be used to aid corroboration of the Columbia Plateau regional dust transport model by: (1) determining if modeled emissions are from given fields or grid areas; & (2) characterizing the mode of transport from given regions. 3a. Studies are part of GRACEnet (Greenhouse Gas Reduction through C sequestration & Carbon Enhancement Network) & REAP (Renewable Energy Assessment Project), established to assess management impacts on greenhouse gas emissions & soil C status. We will assess tillage & crop rotation affects on soil C storage across variable soil & terrain attributes of the WSU Cook Agronomy Farm (CAF). 3b. Two studies will assess management & environmental effects on soil C and N cycling & GHG emissions. The first study (CAF) was previously described in sub-objective 3a. The second study was established in 2001 at the USDA Palouse Conservation Field Station & consists of five different farming systems including no-till, perennial biofuels, organic, & native perennials. These two field studies will be used to assess soil gas (CO2, N2O) flux, N mineralization-immobilization-turnover & soil C accumulation. 4a. A portable wind tunnel will be used to assess differences in windblown sediment & PM10/PM2.5 emissions among tillage & cropping systems established at various locations across the Columbia Plateau. Wind speed profiles will be measured using pitot tubes, sediment catch obtained using an isokinetic vertical slot sampler, & PM10 concentration profiles obtained using DustTrak aerosol samplers. 4b. Field studies at the CAF will evaluate two N management treatments for winter & spring wheat: (1) site-specific N management based on the spatial pattern of input variables; & (2) uniform N management. N use efficiency will be evaluated to monitor cropping system N use, assess N management strategies & identify key areas for improvements. Replacing 5348-11000-005-00D(2/10)
3. Progress Report
Objective 1: To discover the influence of cropping systems on soil aggregation that protect soil from erosion, long-term cropping system studies from three precipitation zones of the Pacific Northwest (PNW) were sampled by USDA-ARS scientists. Samples were characterized for soil aggregation, microbial community structure, enzyme activity, pH, EC and carbon. Greater understanding of management impacts on soil aggregation will aid the development of practices that enhance soil resources by controlling soil erosion and promoting soil C sequestration and improve air quality through mitigation of dust emissions. The long-term sites were also sampled to assess management impacts on soil quality and to further understand soil degradation processes. Objective 2: To understand and predict dust emissions from agriculture, USDA-ARS scientists characterized soil microbial communities in soil and PM10 material at locations across the western US. ARS scientists also worked on improving fingerprint methodology by applying micro-organisms to soil as tracers that could provide a powerful tool for understanding dust emission source and fate. Here, soil containing marked strains of bacteria (tracer organisms) created a unique fingerprint that was identified and traced using microbial analyses. Objective 3: A field was sampled by USDA-ARS scientists to assess topography, micro-climate, crop rotation and tillage management effects on soil C sequestration rates and N cycling. Long-term cropping system studies were identified to assess soil C and N dynamics including greenhouse gas (GHG) flux to understand and measure emissions of GHG’s from agriculture and develop improved technologies and practices to manage emissions. Field studies with different N fertilizers were conducted by ARS scientists to determine if GHG emissions could be reduced with the use of polymer-coated N fertilizers. GHG emissions were monitored weekly to assess emission reductions due to the type of N fertilizer used. Objective 4: In cooperation with Washington State University (WSU) scientists, USDA-ARS scientists initiated a study to assess windblown dust and PM10 emissions from agricultural soils with irrigated cover crops. Data on soil properties and PM10 emissions were collected from two sites in spring 2011 where mustard had been incorporated into the soil the previous winter. This study will aid in developing management practices that suppress dust emissions and improve air quality. Field studies were conducted by ARS scientists to evaluate wheat plant density and N fertilizer effects on N use efficiency (NUE). Preliminary results show that NUE can be increased by targeting wheat stand density and N fertilizer rates to specific field locations.
1. Impact of stricter PM10 air quality standards. Air quality specialists are uncertain whether the stricter PM10 Air Quality Standards being considered by EPA will affect air quality in the region. In cooperation with a regional air quality specialist, ARS scientists found that stricter PM10 Standards may cause more violations of air quality standards in eastern Washington. To comply with stricter PM10 Standards, air quality specialists in the region will rely on the Natural Events Policy to comply with air quality regulations. In addition, the wheat growers must utilize the best available land management practices developed by ARS scientists to reduce PM10 emissions from agricultural lands.
2. Soil organic matter increased in no-till. Stubble burning has been a management tool for irrigated wheat in the Pacific Northwest. Concerns about air quality, however, led ARS scientists in Pullman, Washington, in collaboration with Washington State University scientists, to initiate a 6-year field experiment investigating soil quality of a no-till irrigated winter wheat - spring barley - winter canola rotation with residue retained, mechanically removed, or burned after harvest. Continuous winter wheat planted into plowed burned stubble was included as a check. Soil organic matter increased each year with no-till at the 0 to 8 inch depth. The annual winter grass weed downy brome was problematic for winter wheat in the standing and mechanically removed stubble, but was controlled in the no-till stubble burned and the burn/plow check. Winter wheat yields trended higher in all no-till residue management treatments compared to the burn/plow check; however, all no-till systems lost an average of $389 per rotational ha. Although the performance of no-till or a wheat-barley-canola rotation was not economically viable compared to the conventional tillage wheat rotation, producers can enhance soil quality or decrease the incidence of pests using no tillage and alternate crop rotations.
3. Rapid assay for prediction of residue decomposition. Wheat and barley cultivars that do not rapidly decompose have hindered the implementation of conservation farming systems and reduced-till and no-till seeding in the dryland Pacific Northwest. Additional knowledge on cereal straw decomposition will allow growers to design crop rotations that promote the adaptation of reduced-till and no-till seeding. ARS scientists in Pullman, Washington, in collaboration with Washington State University scientists, have developed a quick method using near-infrared technology to identify the fiber and nutrient composition of spring wheat, winter wheat and spring barley straw as well as predicted the straw decomposition among different crop cultivars. Information on differences in straw decomposition among wheat and barley cultivars will assist growers in selecting cultivars for reduced tillage systems.
4. Weed seeds defend themselves from microbial attack. The weed seed bank can persist for years due to seed dormancy and resistance to seed-decay microbes. Weeds defend themselves in many different ways and in some cases the attacking microbe plays a part. ARS scientists in Pullman, WA, in collaboration with Washington State University scientists have found that certain seed decay microorganisms stimulate the production of a weed seed defense enzyme and make the enzyme even more active. Identifying microorganisms that do not cause this defense response, but do cause seed decay, may lead to crop management strategies that increase seed decay and reduce the weed seed bank. This information can be used by scientists, land managers and others to reduce invasive weeds, promote native plants, and keep cover on the land to reduce wind erosion.
5. Wild oat seed decay rating scale. Wild oat is an annual grass weed that is troublesome in cereal crops throughout North America, Europe and Australia. Few herbicides are available for wild oat control, yet development of weed populations that are resistant to the most commonly used herbicides is widespread. Identifying pathogenic and deleterious microorganisms may lead to crop management strategies that promote weed seed decay and reduce seed longevity, such as altered cultural practices (tillage, rotations, or soil amendments) or by inoculation of soil with deleterious microorganisms. ARS scientists in Pullman, Washington, in collaboration with Washington State University scientists, have developed a method to screen seed fungi for their seed decay potential. Fifteen percent of the seed microorganisms tested resulted in decay symptoms on wild oat seed. A seed-decay rating scale was developed that ranged from 0 to 5. The procedures developed here can be used by scientists and technical personnel to investigate the potential of seed and soil microorganisms to decay seed and development of weed biocontrol.
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