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

The objective of this study was to monitor the response of soil physics, grapevine physiology, and fruit composition to different dosages and forms of CaSO4 (anhydrite, CaSO4, and gypsum CaSO4.2H2O) in synergy with organic matter (biosolids). The experiment was performed for three years (2019 to 2021) in a Merlot vineyard located in a sodic soil of the Bakersfield area. The experiment was carried out as a completely randomized block design, with six treatments replicated four times. Each experimental unit had a 30 × 30 m surface that overlapped with a pixel from Landsat 8. Soil amendments were broadcast in winter 2019/20 (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. 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 in all years. Treatments had similar values in grape soluble solids, pH, and titratable acidity during ripening in 2020 and 2021. Yield was greatest in the 10.2 t/ac gypsum in 2020 and in the 5.1 t/ac gypsum + compost in 2021. Soil infiltration measurements showed that gypsum treatments increased infiltration more than the control or the anhydrite treatments in both years. For vegetation indexes measured from Landsat 8, we determined the Spearman’s correlation with in situ measurements such as ψstem. This parameter associated significantly with various indices. The Green Normalized Difference Vegetation Index (r = 0.56) had strongest correlation, followed by the Normalized Difference Moisture Index (r = 0.54). These results will help evaluate best reclamation practices for San Joaquin Valley vineyards.

Funding Support: American Vineyard Foundation