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 potenti al (LWP), stomatal conductance (g(s)), and net CO2 assimilation (A) we re determined in a high-density peach [Prunus persica (L) Batsch cv. C al Red] subjected to regulated deficit irrigation scheduling. The regu lated deficit irrigation treatment caused clear differences in soil wa ter content and predawn LWP relative to control irrigation treatments. Treatment differences in midday LWP, g(s), and A were also significan t, but not as distinct as differences in predawn LWP. Leaves on trees subject to the deficit irrigation treatment were photosynthetically mo re water-use-efficient during the latter part of the stress period tha n were the nonstressed trees. Midday LWP and g(s) on trees that receiv ed the regulated deficit irrigation treatment did not recover to contr ol treatment values until more than 3 weeks after full irrigation was resumed at the beginning of stage III of fruit growth, because of wate r infiltration problems in the dry soil caused by the deficit irrigati on. The regulated deficit irrigation treatment caused only a 8% reduct ion in trunk growth relative to the control, but resulted in a 40% sav ings in irrigation requirements.