Matching irrigation to vine-water requirements: limitations of using sap-flow technology for scheduling irrigation

International Society for Horticultureal Science
Publication Type:
Journal Article
Acta Horticulturae, 2005, 694 pp. 165 - 171
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Mismatch between water applied during irrigation and that required by the crop for transpiration is a major cause of poor returns per unit water use and of land degradation. Advances in commercial sap-flow gauges should provide opportunities for improving water management in tree-horticulture, but this has not been widely explored. In this study we tested the capabilit of sap-flow guages to detect water stress and, hence a need for irrigation, by withholding water for two months from actively growing, mature grapevines. Withholding irrigation reduced soil-water content in the 1.8m soil-profile by almost 40% compared to where irrigation was maintianed, by the reduced soil-water resulted in only a small decrease in the transpirationdeduced from sap flow throughout the 2-month period. This was despite a 3-fold increase in stomatal resistance and a rise of 1.0 C in leaf temperature for the stressed compred to the continuously irrigated vines. Reasons for this response are not clear, but it is possible that the stressed vines accessed water either directly from the waterble or from its capillary fringe. Withdrawal of irrigation also did not result in yield for the stressed-vines. Other implications of these finding are explored including proposals on weighted crop factor to match irrigation with grape-vine water requirements.
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