ISHS Acta Horticulturae 664: IV International Symposium on Irrigation of Horticultural Crops
PARTIAL ROOTZONE DRYING AND DEFICIT IRRIGATION OF 'GALA' APPLES IN A SEMI-ARID CLIMATE |
| Authors: | T. Einhorn, H.W. Caspari |
| Keywords: | Malus × domestica Borkh., stomatal conductance, water potential, vapor pressure deficit (VPD), abscisic acid (ABA), water use |
| Abstract:
As part of a larger, multi-site study on Deficit Irrigation (DI) and Partial Rootzone Drying (PRD) of apples [Malus x domestica Borkh.], a multi year experiment was designed using ‘Gala’ on M26 to determine the effect of DI and PRD on water use, fruit and shoot growth, yield, fruit quality, stomatal conductance, leaf water potential, and whole-leaf abscisic acid (ABA) concentration. Irrigation was via two drip lines, one either side of the tree row. There were five irrigation treatments: a well watered control, 25 PRD, 50 PRD, 75 PRD and DI. For PRD, the numbers represent the percentage of irrigation volume relative to the control as well as the proportion of the surface area wetted by irrigation. The DI received 50% of the irrigation volume applied to the control, but irrigation was applied to the whole surface area. Water savings of 50% and 25-75% were achieved under DI and PRD, respectively, without negatively impacting fruit size. Total seasonal irrigation volumes were 232 mm, 195 mm, 157 mm and 120 mm for the control, 75 PRD, DI and 50 PRD, and 25 PRD treatments, respectively. Fruit growth rate, final fruit size, and fruit quality at harvest and after cold storage did not differ between treatments. Compared to published data, very low midday values were observed for stomatal conductance and transpiration rates at comparatively high (less negative) leaf water potentials. Effects of several feed-forward processes on apple hydration status in response to high diurnal VPD values (4-6 kPa) and chemical signals are discussed. | |
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