Water extraction and fruit expansion by kiwifruit

Abstract The behaviour of 4-year-old kiwifruit (Actinidia deliciosa (A. Chev.) C. F. Liang & A. R. Ferguson) vines growing in a Springbank soil within the Kerikeri Irrigation Scheme was monitored over the 1982–83 season. Water stress was induced in two vines by withholding irrigation and preventing rainfall recharge. Fruit volume expansion appeared strongly linked to the hydraulic status of the vines and could be described by a simple model whereby fruit either expand at the maximum rate shown on well-watered vines, or not at all if water is limiting. Volume losses resulting from fruit softening after extreme water stress were quickly recovered upon the reapplication of irrigation and could be ignored for modelling the influence of water stress on harvest yields. In the absence of rainfall or irrigation, the readily available moisture in this soil is capable of maintaining unrestricted fruit volume expansion for 10 days in mid summer. This result is extrapolated to other soils within the Irrigation Scheme...