Location: Northwest Sustainable Agroecosystems Research
2019 Annual Report
Objectives
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.
Approach
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
In support of Objective 1, significant progress was made in assessing crop rotation, soil amendment, and tillage effects on soil aggregate stability of dryland cropping systems in the Inland Pacific Northwest. Greater stability of soil aggregates decreases susceptibility to wind erosion. Dry aggregate stability was up to 114 percent greater under no-tillage as compared to tillage-based annual fallow; whereas, crop rotation and bio-solid application had relatively minor impacts.
Model simulations using the Wind Erosion Prediction System (WEPS) were used to assess annual (2009 through 2018) dust emissions from wind erosion across the dryland cropping region of the inland Pacific Northwest. Model simulations indicated annual losses of soil and 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. Developing cropping systems that maintain annual cover and increase aggregate stability are required to reduce the hazard of wind erosion.
Research in support of Objective 2 was completed at the Cook Agronomy Farm Long-Term Agroecosystem Research (LTAR) site, including field-scale soil and plant analyses to assess management impacts on soil health metrics as well as soil carbon, nitrogen, and phosphorus budgets. Long-term incubations to quantify labile soil C pools were found to be highly correlated with an inexpensive, simple analytical method. Complementary research included completed instrumentation of eddy co-variance flux towers for monitoring greenhouse gas flux and in-field lysimeters and flumes for assessing differences in hydrologic cycles between ‘business-as-usual’ and ‘aspirational’ LTAR treatments. Soil tests to determine lime requirements for addressing soil acidification (decrease in soil pH) in dryland cropping systems of the inland Pacific Northwest were evaluated and optimal laboratory tests identified.
Accomplishments
1. Climate change predicted to negatively impact soil organic matter of dryland cropping systems in the inland U.S. Pacific Northwest. Climate change can impact major soil properties such as organic matter, a key indicator of soil health and productivity. An ARS researcher in Pullman, Washington, in collaboration with university scientists, discovered that projected climatic shifts in mean annual temperature and precipitation would result in significant declines in soil organic matter for the dryland cropping systems of the inland Pacific Northwest. Furthermore, climatic drivers were more influential than either tillage regime or cropping system intensity for determining soil organic matter levels. This research amplifies the need to further explore mitigation and adaptation strategies to address climate variability and ensure food security.
2. Agro-ecological class stability decreases in response to climate change projections for the inland U.S. Pacific Northwest. Climate change will impact bio-climatic drivers that control the regional location and distribution of major cropping systems in the inland Pacific Northwest. An ARS researcher in Pullman, Washington, in collaboration with university scientists, discovered that super-imposing projected climatic shifts onto current cropping systems resulted in major impacts on agro-ecological classes. In the inland U.S. Pacific Northwest, the amount of annual fallow significantly increased as cropping systems became less stable, which increased the overall uncertainty of which crops, if any, would be grown. This research finding was the justification for a competitively funded research grant and amplifies the need to further explore mitigation and adaptation strategies to address climate variability and ensure food security.
3. Field emissions of nitrous oxide display high spatial variability and long pulses under two tillage regimes. Nitrous oxide is a major greenhouse gas emitted by agricultural soils in amounts greater than natural systems due to the addition of nitrogen fertilizers. These greenhouse gas emissions are not well understood for individual farms, as emissions are difficult to measure and irregular over farm fields throughout the year. Using two different field methods, an ARS researcher in Pullman, Washington, in collaboration with university scientists, found that annual nitrous oxide emissions were slightly greater than previously thought, occurred primarily during long pulses in the spring, but were highly variable. Furthermore, it was discovered that nitrous oxide emissions were significant with regard to climate change and farmer perspectives. Farmers that increase nitrogen use efficiency will save fertilizer input costs and reduce emissions of nitrous oxide, a major greenhouse gas.
Review Publications
Kostyanovsky, K.I., Huggins, D.R., Stockle, C.O., Morrow, J.G., Madsen, I. 2019. Emissions of N2O and CO2 following short-term water and N fertilization events in wheat-based cropping systems. Frontiers in Ecology and Evolution. 7:63. https://doi.org/10.3389/fevo.2019.00063.
Sharratt, B.S., Kennedy, A.C., Hansen, J.C., Schillinger, W. 2018. Soil carbon loss by wind erosion of summer-fallow fields in Washington’s dryland wheat region. Soil Science Society of America Journal. 92(6):1551-1558. https://doi.org/10.2136/sssaj2018.06.0214.
Zhang, X., Sharratt, B.S., Lei, J., Wu, C., Zhang, J., Zhao, C., Wang, Z., Wu, S., Li, S., Liu, L., Huang, S., Guo, Y., Mao, R., Li, J., Tang, X., Hao, J. 2019. Parameterization schemes on dust deposition in northwest China: model validation and implications for the global dust cycle. Atmospheric Environment. 209:1-13. https://doi.org/10.1016/j.atmosenv.2019.04.017.
Pi, H., Huggins, D.R., Sharratt, B.S. 2019. Dry aggregate stability influenced by soil type, crop rotation, soil amendment, and tillage in the Columbia Plateau. Aeolian Research. 40:65-73. https://doi.org/10.106/j.aeolia.2019.07.001.
Pi, H., Sharratt, B.S., Lei, J. 2018. Wind erosion and dust emissions in central Asia: Spatiotemporal simulations in a typical dust year. Earth Surface Processes and Landforms. 44(2):521-534. https://doi.org/10.1002/esp.4514.
Webb, N., Chappell, A., Edwards, B., McCord, S.E., Van Zee, J.W., Cooper, B., Courtright, E.M., Duniway, M., Sharratt, B.S., Tedela, N., Toledo, D.N. 2019. Reducing sampling uncertainty in aeolian research to improve change detection. Journal of Geophysical Research. 1-12. https://doi.org/10.1029/2019JF005042.
