The 2011 ASHS Annual Conference

Regulated deficit irrigation (RDI) is an irrigation strategy to manipulate yield, quality and vegetative growth with water stress at specific phenological stages. Regulated deficit irrigation has been used in some fruit crops to improve water use efficiency, control vegetative growth, and maintain or improve fruit quality. A few regulated deficit irrigation trials with oil olive varieties have been conducted in Europe but little research is available for high density olive oil production under California conditions.  Therefore, we conducted a 3-year study to determine the effects of 4 different RDI treatments (40% ETo, 30% ETo, 20% ETo, and a variable ETo treatment) and 2 different soil types (loam and grvelly loam) on oil production, fruit yield, fruit set, and fruit size. RDI treatments produced similar fruit yields and oil production in 2009 and 2010; however, the more water stressed treatments produced significantly greater oil production per ton of fruit.  Shoot extension growth was significantly reduced in the 20 and 30 ETo treatments compared with the 40 ETo.  This is important because fruit are produced on previous year's wood.