Noelymar Gonzalez-Maldonado,* Erika Yao, Luisa Robles, Kerri Steenwerth, Mallika Nocco, and Cristina Lazcano
*University of California Davis, 1110 Plant and Environmental Sciences Building, LAWR, One Shields Ave, Davis, CA, 95616 (ngonzalezmaldonado@ucdavis.edu)

Vineyard soils are strongly vulnerable to degradation from intense climate events like heavy rainfall and droughts. Soil health (SH) plays an essential role in building vineyard resilience, climate regulation, and sustainable winegrape production. From previous interviews, growers identified static soil properties (like parental material and texture) as the most important soil components of terroir. However, SH involves dynamic soil properties (organic matter, nutrients, and biota, among others), which are sensitive to management and can impact vine health and productivity. Our goal was to identify what SH indicators are most relevant for winegrape production and how they vary across soil types through collaborative research with growers in the Napa and Paso Robles regions of California. Growers identified two contrasting soils and rated them as “ideal” and “challenging” for achieving their vineyard goals. We collected soil samples from the tractor and vine rows at two depth intervals (0 to 10 and 10 to 20 cm) across 32 vineyards in the Napa Valley AVA and 30 vineyards in the Paso Robles AVA. The SH indicators evaluated were total C, active C, microbial respiration, MBC, PLFAs, PMN, inorganic N, pH, bulk density, penetration resistance, wet aggregate stability, and infiltration rate. Data analysis included descriptive statistics, generalized mixed model, and Pearson correlations. We expect to see a significant difference between growers’ ratings, with ideal soils having higher levels of organic matter pools, biodiversity and biological activity, aggregate stability, and infiltration rates. We also expect lower levels of compaction in the ideal soils, as well as trends and significant differences across different soil types (i.e., textural classes) with clay % being a potential driver of SH indicator levels. This research will help us identify what soil health indicators are most relevant for vineyards and provide ranges of soil health indicator variability by soil type for growers.

Funding Support: American Vineyard Foundation, Western SARE