ISHS Acta Horticulturae 297: II International Symposium on Kiwifruit
IRRIGATION MANAGEMENT FOR OPTIMUM KIWIFRUIT SIZE |
| Authors: | K.J. McAneney, P.T. Prendergast, M.S. Astill |
| Keywords: | Priestley and Taylor, evapotranspiration, water balance, water application methods |
| Abstract:
Previous work on orchard water relations is briefly reviewed and the results of a new study presented which show evaporation from a well-watered and sheltered kiwifruit orchard in Northland to occur at the equilibrium rate (Eeq) i.e. at approximately 0.75 of the Priestley and Taylor estimate. Moreover, in this humid coastal climate the rapid onset of dewfall after sunset prevents night-time water use. This contrasts with other work showing that nocturnal water use may, on occasions, represent 20 – 25% of the daily water economy of a kiwifruit plant. Fruit expansion, which has previously been shown to be very sensitive to water availability, was unresponsive over 4 seasons to different irrigation application methods wetting between 19 and 30% of the potential soil rooting zone. Root growth seems sufficiently dynamic to cope with differences in water distribution of this magnitude. Lastly a simple water budgeting scheme is proposed which reduces management decisions to a simple question of whether or not to irrigate. In the absence of rainfall, daily irrigations are delivered at the long-term average monthly Priestley and Taylor (or Penman) evaporation figures (≈1.3Eeq). Threshold tensiometer readings are used to decide when to begin irrigating after rain. The approach is conservative, and has proved effective and much easier to use than daily water budgeting using a water balance. | |
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