of fruit trees has highlighted the potential of using various forms of deficit irrigation in the water management of orchard and vineyards (Fereres et al., 2003).

Regulated Deficit Irrigation

We define regulated deficit irrigation (RDI) as a regime that purposely stresses the trees or vines at specific developmental stages of the crop such that there is little, if any, negative impact on the yield of marketable product and/or profits. The water stress is normally imposed at stages of the season when reproductive growth is relatively low. The water stress results in lower tree water status, partial stomatal closure, which reduces ET (Fig. 1). The objective of RDI is to maintain or increase farm profits while reducing the consumptive use of water.

FIGURE 1 Impact of progressively more severe deficit irrigation from July 10 to August 1 on a) midday stem water potential, 2) midday stomatal conductance, and 3) ET of mature peach. Control was fully irrigated. Deficit trees returned to full irrigation on August 2. Adapted from Goldhamer et al. (1999), Fereres et al. (1999), and Mata et al. (1999).



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