Shrinivasa Upadhyaya,* Kelley Drechsler, Erin Kizer, Channing Ko-Madden, Julie Meyers, and Qingsong Zhang  
*Biological and Agricultural Engineering Department, University of California, Davis, CA 95616 (skupadhyaya@ucdavis.edu)

A management zone-based precision irrigation scheme that used specially developed leaf monitors to sense vine water status was implemented in an E & J Gallo Wineries vineyard located in Galt, CA, during the 2016 growing season. The experimental plot was divided into two management zones using unsupervised fuzzy classification based on soil and plant characteristics (texture, digital elevation, electrical conductivity, yield, and vegetation index). Twelve leaf monitors were deployed to measure vine water status. Each leaf monitor continuously sensed the temperature of a shaded leaf along with relevant environmental factors to develop an index that correlated with vine water status. Data from these leaf monitors were complemented by soil moisture sensors, pressure sensors, and flow meters. Latching solenoid valves were used to control water supply lines to manage irrigation. These sensors and controllers were connected to hubs with cellular modems to up-load the data to the web so that the data can be accessed from computers or mobile devices from anywhere web access was available. The same system was also used to remotely actuate latching solenoid valves to manage irrigation. Throughout the season, precision irrigation management based on vine water status and an evapotranspiration (ET)-based grower irrigation were implemented. In the vine water stress-based precision irrigation scheme, attempts were made to maintain a leaf water potential (LWP) of -13 bar during the veraison period and -12 bar pre- and postveraison as per grower recommendations. Around 50% of ET requirements were needed during the veraison period to maintain desired LWP. Preliminary results show that overall vine water stress-based precision irrigation required 69% of ET-based grower irrigation amount. Yield and several quality attributes including Brix values were also collected and results will be included in the presentation.

Funding Support: E & J Gallo Wineries and California Department of Food and Agriculture