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.
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