Water use of plum trees ( Prunus salicina) trained to four canopy arrangements

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Water supply is a limiting factor in the production of stone fruit in the Mediterranean climate of South Western Australia. Fruit growers are adopting intensive orchard systems and are using a variety of canopy training methods. To establish whether the training system was likely to have a strong influence on water use, we studied the soil water balance and plant water status of 6-year-old plum trees (cultivars ‘Laroda’ and ‘Santa Rosa’) trained to Lincoln, Vase, Palmette and Tatura trellis systems, and growing on a loamy sand. When trickle irrigated at 110% class A pan evaporation rate, the Tatura trellis used more water than the other systems, but the differences were small, being 9–12% between training systems. Trees with a high crop load used slightly more water than those with a low crop load. There were no significant differences between the two cultivars in their water use. When irrigated after harvest at 40% of A pan, the Vase system used more water than the other systems, but again differences were small (∼ 18%). When water was withheld for a week in a period of high evaporative demand (7.3 mm day −1), the Tatura and Palmette systems used more water than the Lincoln trees. This was associated with their ability to extract water from deeper layers in the soil. When well watered, the trees used 75–99% of the intercepted net radiation for evaporation of water. As differences in canopy water use were not large, but yield differences were considerable (34 t ha −1 for the Vase cf. 62 t ha −1 for the Tatura trellis), the efficiency of water use will be greatest on those canopies giving the greatest yield.