Efficient Water Use in Ontario Apple Orchards Through Evapotranspiration-based Irrigation Scheduling and Drought Tolerant Rootstocks
Maintaining tree growth and fruit production during periods of drought stress are important issues for apple producers. Apple trees were subjected to five irrigation treatments including three rates based on evapotranspiration, a commercial rate of 25.4 mm/week (positive control), and a rain-fed treatment (untreated). Irrigation treatments did not significantly affect marketable yield, fruit size, or trunk cross-sectional area (TCSA). In 2013 fruit quality was unaffected by irrigation; however, in 2014 the rain-fed treatment delayed maturity and increased the colour intensity of harvested fruit. When four rootstocks were evaluated for drought tolerance Vineland 3 (V.3) was observed to be unique for several physiological traits related to drought tolerance, including a greater retention of biomass and TCSA compared to the other genotypes, and stability in its leaf area:TCSA ratio and root:shoot ratios. The critical relative soil water contents of the four genotypes were also determined but there were no genotypic differences.