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. Soil was collected and soil quality parameters analyzed from soil and aggregates from dryland management practices. In addition, analyses of soil organic matter, soil biology and soil quality were conducted from long-term cropping systems plots. Objective 2. Scientists are characterizing microbial communities in soil and particulate matter with a diameter of 10 micrometers or less at locations across the western United States to understand dust emissions. These 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. Soil containing marked strains of bacteria (tracer organisms) created a unique fingerprint that was identified and traced using microbial analyses. Objective 3. Analyses of data from field study sampled by ARS scientists at Pullman, Washington, were continued that assess topography, micro-climate, crop rotation and tillage management effects on soil carbon sequestration rates and nitrogen cycling. Long-term cropping system studies were identified to assess soil carbon and nitrogen dynamics including understanding and measuring emissions of greenhouse gasses from agriculture and developing improved technologies and practices to manage these emissions. A static chamber study with automated greenhouse gas flux measurements was field-deployed with different water and nitrogen treatments. Objective 4. Scientists completed the second year of data from an oilseed cropping system study. Data on soil properties and PM10 (particulate matter with a diameter of 10 micrometers or less) emissions were collected at Lind and Ritzville, Washington, in autumn 2012, where camelina and safflower were grown in rotation with wheat. Information generated from this study will aid in assessing the environmental impact of growing oilseed crops in the Columbia Plateau. Soil was collected and soil quality parameters analyzed from dryland management practices. Field studies at a farm near St. John, Washington, were conducted by ARS scientists to evaluate wheat plant density and nitrogen fertilizer effects on nitrogen use efficiency. Precision nitrogen management field studies were continued at the Wilke Farm near Davenport, Washington. Preliminary results show that nitrogen use efficiency can be significantly increased by targeting wheat stand density and nitrogen fertilizer rates to specific field locations.
1. Drought conditions ameliorated by standing crop stubble. No-tillage is less prevalent than conventional-tillage in managing agricultural lands throughout the Unites States and is in part due to a lack of knowledge regarding no-tillage technologies. ARS scientists in Pullman, Washington, discovered that standing crop residues in no-tillage reduces field drifting of snow and results in greater and more uniform storage of soil water as compared to conventionally tilled fields. The greater soil water storage from maintaining standing stubble decreased drought in the following crop and increased potential wheat yield. These findings will promote the adoption of no-tillage for reducing drought levels and soil erosion as well as enhancing crop yields and agricultural sustainability.
2. Soil carbon sequestration quantified for Pacific Northwest agriculture. ARS scientists at Pullman, Washington, assessed agricultural impacts on soil organic carbon sequestration using published data for different agroclimatic zones of the Pacific Northwest. We discovered that these data were quite variable and devised methodology to express cumulative probabilities of soil carbon change that could be useful for policy makers and marketers to assess the influence of land management changes on soil carbon. These analyses showed that 75% of the converted native ecosystems have lost at least 0.14 to 0.70 Mg carbon per hectare, per year, depending on the agroclimatic zone. Converting from conventional tillage to no-tillage was predicted to increase soil organic carbon from 0.12 to 0.21 Mg carbon per hectare, per year for 75% of situations and was also agroclimatic zone specific. Compared to annual cropping systems, mixed perennial-annual systems would be expected to have soil organic carbon gains of at least 0.55 Mg carbon per hectare, per year for 75% of sites. The variability found among studies suggests that a well validated carbon model for the region would aid evaluation of soil organic carbon changes due to management particularly for specific farms and sites with unique soil organic carbon history and circumstances.
3. Greenhouse gas emissions assessed for dryland agriculture in Washington. ARS scientists at Pullman, Washington, simulated agricultural impacts on soil organic carbon sequestration and nitrous oxide emissions in eastern Washington using the CropSyst model. Conversion from conventional tillage to no tillage produced the largest relative increase in soil organic carbon storage where increased rates of soil organic carbon storage ranged from 0.29 to 0.53 Mg carbon dioxide equivalent per hectare, per year. The changes in soil organic carbon storage were less with lower annual precipitation, greater amounts of fallow and with changes from conventional tillage to reduced tillage. Simulated nitrous oxide emissions were not very different under conventional, reduced and no tillage. However, nitrous oxide emissions were sufficiently high to offset gains in soil organic carbon from reduced and no tillage, indicating that improved nitrogen management in all systems could contribute to greenhouse gas mitigation. These results will be useful for wheat growers, the Natural Resources Conservation Service (NRCS), Conservation Districts, US Environmetal Protection Agency (USEPA), scientists, and the fertilizer industry, as understanding the effectiveness of agricultural greenhouse gas mitigation strategies is critical for addressing climate change and managing soil sustainability.
4. Long-term Agroecosystem Research site established at Pullman, Washington. Scientists from Pullman, Washington, were successful in establishing a Long-term Agrocecosystem Research site. This site, located at the Washington State University Cook Agronomy Farm, was one of ten sites selected to be a part of the Long-term Agroecosystem Research network across the United States. Scientists associated with the network have written a document outlining a vision for ARS long-term agroecosystem research. This network will address critical national issues in agricultural sustainability that require long-term research assessments.
5. Antibiotics do not affect the function of vegetation filter strips. Scientists in Pullman, Washington, and Columbia, Missouri, determined that microbial community structure and function along vegetation filter strips were not affected by the addition of antibiotics to these filter strips. Vegetation filter strips along water ways are critical for maintaining water quality, but the addition of antibiotics to vegetation filter strips is a concern in regions where manure (containing antibiotics) is applied near the filter strips. Our results suggest that field application of manure with antibiotics will not affect the intended function of the filter strips. Therefore, they do not pose harm to humans or to the environment.
6. Soil crust formation can be predicted from rainfall. Regional assessments of wind erosion are dependent on correctly simulating the formation of soil crusts in response to rainfall in the Columbia Plateau. ARS scientists at Pullman, Washington, found that crust thickness of five major soil types across the Columbia Plateau can be adequately estimated from rainfall. We found that crust thickness exponentially increased with rainfall. This relationship can be used to improve the performance of the USDA-ARS Wind Erosion Prediction System (WEPS) in the Columbia Plateau.
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