PHYSIOLOGICAL, GROWTH, YIELD AND QUALITY RESPONSES OF ´SHIRAZ´ BERRIES MANIPULATED USING PRD AND DRIP IRRIGATION

Abstract

A study was conducted to investigate the effect of partial rootzone drying (PRD) in comparison to drip irrigation with two different water levels (0.45 and 0.9 ETc) on the physiological, growth, yield and quality responses of nine-year old 'Shiraz' grapevines in north-eastern Victoria, Australia. The amount of water rather than the application of PRD had a more significant effect on vine response. Average berry weight was unaffected but yield and berry number was reduced through influences that arose the previous season as well as the current season. There was some evidence that the application of PRD resulted in the maintenance of leaf function as measured by photosynthesis, transpiration and stomatal conductance pre- and post-veraison, however, this difference was not reflected in yield or growth parameters. As indicated by high pH and low acid levels the relatively high evaporative demand and small rooting volume of the vines at this site resulted in the vines experiencing repeated periods of stress between irrigations. The contrasting results of different PRD studies, including this trial, clearly indicate that the response of vines to PRD treatments is not easily defined and that vine management, soil types, irrigation amount and climate play a critical role in a grapevine's response to PRD. At this high stress site vines irrigated near or below potential crop evapotranspiration (Et-c) did not respond to PRD.