John Wilson, Qun Sun,* Shijian Zhuang, Zhi Wang, and Lauren Hale
*California State University, Fresno, 3547 Trenton Ln., Clovis, CA, 93619 (qsun@csufresno.edu)

San Joaquin Valley is facing drought and saline soil conditions, which adversely affect vine growth and yield. There are ~3000 to 5000 L of wastewater generated per metric tonne of crushed grapes every year. Winery wastewater has high organic load, low pH, and variable salinity and nitrogen levels, which can harm soil physical and chemical properties and reduce grape yield and fruit quality. Excessive N can also be leached into the groundwater, causing contamination. The objectives of this study were to examine the effects of cover crop on soil properties; determine the impact of cover crop on vine canopy growth, yield, and grape quality; and promote effective water and soil management in the framework of sustainable viticulture. Mature Ruby Cabernet vines (8-years-old) near Fresno, CA, were trained on quadrilateral cordons using a spur-pruned trellising system. Vines were grafted on Freedom rootstock and planted at 4’ by 10’ with the cordon height at 52” above the vineyard floor. Randomized complete block design was applied, with eight treatments replicated four times. Treatments were 1) Control: no-tilled with residential vegetation; 2) Tilled; 3) UC 937 Barley; 4) WB Patron Wheat; 5) Pacheco Triticale; 6) Sierra Oats; 7) Rye grass; and 8) Dairyland Magnum Salt Alfalfa. Each experimental unit consisted of one quarter-mile long vine row. The vineyard was furrow-irrigated using wastewater before planting the cover crop. Based on the first year’s study, cover crop significantly affected soil chemical composition. Barley, oat, rye grass, triticale, and wheat sequestered carbon more than the control, by 200 to 400 kg/acre. Oat, rye grass, triticale, and wheat absorbed N more than the control, by 6 to 10 kg/acre. Barley and rye grass absorbed sodium more than the control. Triticale and wheat reduced soil EC. Rye grass, triticale, and wheat lowered soil Na. No treatment affected microbial biomass in the first year. The project is still ongoing, and additional data will be provided in the next two seasons.

Funding Support: Agricultural Research Institute