Postharvest deficit irrigation (PDI) is a strategy that can be used to reduce water demands in sweet cherry orchards and is a more sustainable irrigation strategy that will support agriculture resilience to climate change. Previous studies in this region have reported no change in plant physiology or tree growth with irrigation volume reductions of up to 25 %, postharvest. However, the effects of more severe postharvest reductions in irrigation volume were unknown.
This project compared the effects of three irrigation treatments over a three-year period (2019-2021) in five commercial sweet cherry orchards that ranged in elevation and latitude across the Okanagan Valley, BC, Canada:
- A control of full irrigation, irrigated according to conventional growers’ practice at each orchard
- PDI-30 with 27-33 % reduction in irrigation volume, after harvest (67-73 % of control)
- PDI-50 with 47-52 % reduction in irrigation volume, after harvest (48-53 % of control)
Soil moisture, plant stem water potential, photosynthesis, tree growth, flower bud spring phenology, flower bud moisture content and cold hardiness, and fruit yield and quality (at harvest and after cold storage and shelf-life conditions) were assessed to determine if PDI altered fruit development over the subsequent growing season. A cost-benefit analysis of postharvest deficit irrigation implementation in the Okanagan Valley was also developed.
Cold hardiness data collected during this study was used to develop and validate models that predict the temperatures that cause lethal damage to the sweet cherry cultivars ‘Sweetheart’ and ‘Lapins’ throughout the dormant season. These cold hardiness predictive models will provide a decision support tool for growers. This tool will be beneficial when faced with making potentially costly frost management decisions and may be especially useful to growers interested in expanding sweet cherry production into more extreme growing sites in the face of a changing climate.
Key findings included:
- In the growing season following treatment application, PDI had no effect on stem water potential or photosynthesis in any year and at any site; there were also no effects of PDI treatment on tree growth.
- Neither PDI-30 nor PDI-50 caused changes in the timing of flower bud phenology, cold hardiness or moisture content relative to the control.
- PDI treatments had no overall effect on fruit yield or fruit quality at harvest or after storage and shelf-life conditions.
- The cost-benefit analysis revealed that the costs of implementing PDI are minimal but bring benefits for the grower and society in conserving water.