The concept of RDI has been the subject of UC research for decades. Traditionally in irrigated agriculture, farmers give crops all the water they can drink. RDI relies on research that shows exactly when farmers can withhold water from crops and when to irrigate for maximum water efficiency.
Paul Verdegaal, UC Cooperative Extension advisor in San Joaquin County, said water deficits at the right time in plant and fruit development can improve berry quality, especially in red wine varieties, by intensifying color and flavor. Slight deficits also limit excessive growth of shoots and leaves that can affect diseases, such as bunch rot.
"So far the crop doesn't seem all that much lighter than average," Vergegaal said. "Most growers who have been using RDI for the past several years have seen very good quality of fruit and little to no difference in yields from years past.”