Drip irrigation scheduling for container grown trees based on plant water status

In typical ornamental nurseries, irrigation schedules are frequently established subjectively, often resulting in excessive water use and significant fertilizer leaching. Using stem psychrometers to directly measure plant water status (PWS), the relationship between water stress, prevailing environmental conditions, and species-specific stress-tolerance thresholds was characterized. Irrigation-scheduling based on predicted plant water status thresholds correlated to cumulative daily environmental conditions (i.e., cumulative vapour-pressure deficit) were tested on Serviceberry ( Amelanchier laevis ) grown in a drip irrigated pot-in-pot production system. Three irrigation treatments were applied: (1) conventional practice (control), (2) moderate restriction/stress, and (3) high restriction/stress. The moderate and high treatments reduced water consumption by 46 and 63%, respectively. Trees within the control and moderate irrigation treatments did not differ in stem caliper, while trees within the high stress treatment trees grew slower but otherwise appeared healthy. This study demonstrated that irrigation schedules based on predicted PWS thresholds significantly reduced water use without impacting plant growth and quality.