Khushwinder Singh, Paolo De Censi, and Luca Brillante*
*Department of Viticulture and Enology, California State University Fresno, 2360 E Barstow Ave, Fresno, CA 93740 (lucabrillante@csufresno.edu)

Alleviation of salt-related problems is crucial to increase soil health in the San Joaquin Valley of California. This study monitored the response of soil physics, grapevine physiology, and fruit composition to different dosages and forms of CaSO4 (anhydrite [CaSO4] and gypsum [CaSO42H2O]) in synergy with organic matter (biosolids). The experiment was performed for two years, 2020 and 2021, in a Merlot vineyard located near Bakersfield with a sodic soil. The experiment was a completely randomized block design with six treatments replicated four times and broadcast in winter 2020 (2.5 t/ac gypsum, 5.1 t/ac gypsum, 10.2 t/ac gypsum, 5.1 t/ac anhydrite, and 5.1 t/ac gypsum + biosolids) after the first season of measurements to ensure no differences across treatments before application. Each experimental unit has a 30 × 30 m surface that overlaps with a pixel from Landsat 8. Biweekly measurements of stem water potential and leaf gas exchange showed moderate to severe water stress but did not evidence significant differences across treatments in plant water status, carbon assimilation, stomatal conductance, or water use efficiency. Treatments had similar values in grape soluble solids, pH, titratable acidity, and anthocyanin profile measured during ripening. The yield was greatest in the 10.2 t/ac gypsum and 5.1 t/ac gypsum + compost treatments. Soil infiltration measurements showed that gypsum treatments increased infiltration more than the control or anhydrite treatments. The Normalized Difference Vegetation Index measured from Landsat 8 decreased during the sea-
son and the Crop Response to Salinity Index had a strong but similar drop during preveraison at the time of greatest water stress. We expect more differences across treatments to manifest in year two, as the reaction of soil amendments in the soil is a slow process.

Funding Support: American Vineyard Foundation