Deficit irrigation, or RDI (regulated deficit irrigation) is a word that's being thrown around quite a bit, says Rhonda Smith, Sonoma County farm advisor. But, by default, Smith said, all grape growers deficit irrigate their vines."Whether you're a raisin grower in Caruthers or a wine grower in Napa, you would never give your vines everything they could use. If you give a grapevine all the water it could use, yield and quality do go down," she said.Research indicates that one may deficit irrigat...