PATTERNS OF SOIL AND TREE WATER STATUS AND LEAF FUNCTIONING DURING REGULATED DEFICIT IRRIGATION SCHEDULING IN PEACH

Seasonal patterns of soil water content and diurnal leaf water potential (LWP), stomatal conductance (g(s)), and net CO2 assimilation (A) were determined in a high-density peach [Prunus persica (L) Batsch cv. Cal Red] subjected to regulated deficit irrigation scheduling. The regulated deficit irrigation treatment caused clear differences in soil water content and predawn LWP relative to control irrigation treatments. Treatment differences in midday LWP, g(s), and A were also significant, but not as distinct as differences in predawn LWP. Leaves on trees subject to the deficit irrigation treatment were photosynthetically more water-use-efficient during the latter part of the stress period than were the nonstressed trees. Midday LWP and g(s) on trees that received the regulated deficit irrigation treatment did not recover to control treatment values until more than 3 weeks after full irrigation was resumed at the beginning of stage III of fruit growth, because of water infiltration problems in the dry soil caused by the deficit irrigation. The regulated deficit irrigation treatment caused only a 8% reduction in trunk growth relative to the control, but resulted in a 40% savings in irrigation requirements.