CALIBRATING SOIL HEALTH METRICS FOR WASHINGTON STATE S PRIMARY WINE GRAPE GROWING REGION

Molly McIlquham

doi:10.7273/000004564

Soil health, the ability of a soil to function as a living ecosystem and sustain plants, animals, and humans, has been extensively studied in the Midwest and Northeastern U.S. in rainfed annual cropping systems. However, information is lacking for improving and assessing soil health in irrigated specialty cropping systems, especially for wine grape (Vitis vinifera L.) growers in the Pacific Northwest, where soil health threats and cropping goals are drastically different. Soil physical, chemical, and biological properties related to important functions are assessed through indicator measurements, but regional targets for each measurement must be established to account for the effects of inherent soil type and climate. Additionally, guidance on how management practices may influence soil properties in the drip-irrigated vineyards must be evaluated. To address this gap in knowledge, a soil health assessment was conducted across Washington state’s primary wine grape growing region, sampling 70 sites with varying management and measuring 14 soil health indicators. Producers provided guidance on “good” and “challenging” field pairs and participated in questionnaire-led interviews to gather management histories for each block. Preliminary scoring curves were developed for soil health indicators measured. Curves for permanganate oxidizable carbon and soil protein were shifted negatively from scoring curves being used across the U.S. due to inherent differences in soils and climate. Soil health changes from management practices were also analyzed, and compost additions increased potentially mineralizable nitrogen and cation exchange capacity. No differences in soil health indicators were detected as a result of managing alleyway vegetation. The nature of the study allowed for a considerable variation in the establishment of alleyway vegetation and compost application rates, therefore decreasing the power to detect changes. Indicators unique to Vitis vinifera in Washington state include measuring northern root knot nematode (Meloidogyne hapla); however, no management practices affected the populations. No measured soil health differences were detected between farmer identified “good’ and “challenging” pairs. Data collected from this soil health assessment will provide growers with attainable measured soil health ranges disseminated through an Extension publication and provide a framework and guidance for further research on soil health management in vineyards.

CALIBRATING SOIL HEALTH METRICS FOR WASHINGTON STATE S PRIMARY WINE GRAPE GROWING REGION

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