Automated cycled sprinkler irrigation system for frost protection of apple buds

An automated cycled overtree sprinkler irrigation system was implemented and tested in a 0.4 ha (1 acre) dwarf apple orchard to protect apple buds from cold temperatures. The system reduced water usage compared to a more conventional approach of continuous sprinkling. The control scheme was based on a system that monitored the environmental parameters (air temperature, wind speed, relative humidity) and bud temperatures, calculated the on and off times, and cycled the valve. The system was tested during three frost events in the spring of 1997. The control system successfully kept the bud temperatures above the critical level during two of three frost events. During one event the sprinkled orchard temperatures dropped below the critical temperature for a short duration but were warmer than the unsprinkled orchard temperatures. The average reduction in water during the three frost events tested was about 72% as compared to continuous water application using the same system.