Regulated deficit irrigation for California canning olives

Three regulated deficit irrigation (RDI) treatments were imposed on mature olive trees (Olea europea cv. Manzanillo) for four seasons in the San Joaquin Valley of California and tree performance was compared with a fully irrigated Control. The RDI regimes imposed deficit irrigation generally during June and July. Drip irrigation was used on trees with a spacing of 4.57 x 9.14 m. The RDI regimes resulted in mean seasonal applied water of 645, 579, and 432 mm per season; reductions of 16.2, 24.8, and 43.9% from the 770 mm for the Control (determined using previously established crop coefficients and real-time reference crop water use). Predawn leaf water potential (tree water status) generally reflected differences in applied water. Mean values for the four experimental years of fruit load, fresh and dry fruit weight, and fruit value were not statistically different. However, due to the impact of lower fruit load, fresh weight, and fruit value with the most severe RDI regime in the highest "on" alternate bearing year, mean gross revenue was significantly less (24.6%) than the Control. Results to date suggest that the RDI regime that saves about 25% (200 mm) of full ETc may be useful in conserving water while maintaining top yields of high quality fruit.