Irrigation management to enhance the quality, efficiency, and survival of transplanted nursery trees

The tree nursery industry is the largest water consumer in the ornamental horticulture sector in Canada. In most nurseries, subjective irrigation scheduling protocols have conditioned the trees to receive daily irrigation, however, rising environmental concerns and cost of water have prompted the industry to reduce its use of water. These water saving effects on plants still remain uncertain. This study examined the effects on tree growth, tree size and price changes due to water savings in Acer rubrum and Thuja occidentalis in a container production system. Nursery standard, mild, moderate, and high water stress treatments were applied via drip irrigation and based on cumulative vapour pressure deficit (CVPD) thresholds previously established. The leachate mass (kg) was collected from each stress treatment and compared to the nursery standard to establish relative changes in water savings. Tree growth was measured as caliper (Acer rubrum) or height (Thuja occidentalis) and the influence on selling pricing of the tree was determined. Acer rubrum exhibited a water savings of 50, 74 and 81% from the mild, moderate and high stress treatments respectively which resulted in a: 15% increase, 16% decrease, and 58% decrease in mean caliper growth (mm) this season. The reduction in tree caliper did not affect the final selling price. Thuja occidentalis had exhibited a water savings of 68, 84, and 89% from the mild, moderate, and high stress treatment, this reduced height growth by 36, 57, and 80%, respectively, which resulted no change in price for this season. These preliminary results indicated that each species have different water requirements. Acer rubrum caliper did not benefit from excessive application of water while Thuja occidentalis heights were more dependent on the water application. Significant water savings were realized in both cases which resulted in no economic penalties. Water savings over several seasons may allow nursery plants to improve survivability by conditionling. Additional work needs to be done to further confirm the plantsRSQUO water usage characteristics and further refine irrigation management practices.