Calibrating Soil Health Indicators for Washington State Winegrape Systems
Molly McIlquham,* Kwabena Sarpong, Dani Gelardi,
Leslie Michel, Teal Potter, Clark Kogan, and Deirdre Griffin
LaHue
*Washington State University, 16650 WA-536, Mount Vernon, WA,
98273 (molly.mcilquham@wsu.edu)
Commodity crop growers in the Midwestern and Northeastern United States can effectively evaluate their soil health using recommendations based on extensive research on typical ranges and benchmark values for physical, chemical, and biological soil health indicators in these areas and crops. However, for growers of specialty crops, such as winegrapes (Vitis vinifera) in the Pacific Northwest, there is little information on regional and crop-specific soil health indices or guidance on how management practices may influence soil properties and the surrounding ecosystem. Therefore, this study aims to (1) calibrate soil health indicator scoring curves and benchmark values and (2) explore how management practices may impact soil health in Eastern WA’s arid winegrape growing region. We used a survey approach to sample 70 producer-identified paired “good” and “challenging” winegrape vineyard blocks across Washington state’s Columbia Basin. Soil sampling occurred midseason, between bloom and veraison, for a suite of soil health indicators, such as permanganate oxidizable carbon (C), mineralizable C, potentially mineralizable nitrogen, bulk density, ACE soil protein, pH, and texture. Additionally, we measured available water-holding capacity and parasitic nematodes. These indicators are not always included in basic soil health tests, but may be critical properties in irrigated winegrape systems. Producers provided management histories for each block through questionnaire-led interviews. Using precipitation, sand content, and soil strata as covariates, we calculated effect sizes and confidence intervals to determine the effects of management on soil health indicators and create scoring curves calibrated to Washington State’s primary winegrape growing region. As the first coordinated soil health assessment in Washington State in winegrapes, this study will provide a framework and guidance for further research on soil health relationships. Ultimately this study will guide producers to make informed decisions on soil management in inland Pacific Northwest winegrape systems.
Funding Support: Washington State Department of Agriculture Specialty Crop Block Grant
