Growth, fruit yield and quality of Golden Delicious apple trees under fixed partial rootzone drying

Abstract: We investigated the vegetative and productive responses of 'Golden Delicious' apple (Malus domestica Borkh.) trees to fixed partial rootzone drying under the dry climate of central Sicily. Soil water content (SWC), stomatal conductance, yield, fruit quality, fruit growth, and vegetative growth of conventionally irrigated trees (CI), where drip emitters on both sides of each tree were left open, were compared to that of fixed partial rootzone drying (FPRD) trees where only one side of the rootzone was irrigated for the entire season thus receiving 50% of the CI irrigation water. The irrigation season started on 31 July and ended on 13 September, 2004. Wet and dry rootzone sides showed significantly different SWC from 16 August until 14 September, whereas stomatal conductance of CI and FPRD trees differed significantly starting on 24 August. Relative growth rate of CI fruit was higher than that of FPRD fruit on 27 and 31 August, but fruit size was similar during the entire sampling period and at harvest. Trees of the two treatments had similar yields, number of fruits, crop load, fruit:leaf ratio, fruit quality, tree height, wood fresh and dry weight, canopy spread area, volume and density, shoot length and number, internode length, and leaf area. FPRD trees had higher yield efficiency, thinner shoots, lower leaf water content, higher canopy density and leaf dry weight and specific leaf weight than CI trees. Our observations suggest the extent of possible water savings without loss of yield and fruit quality using this partial rootzone drying strategy in 'Golden Delicious' apple orchards of central Sicily.