Targeted frost protection - Orchard trials

Abstract

This study investigates the viability of targeting water onto fruit trees for frost protection, thus virtually eliminating unnecessary application to inter-row areas. An orchard trial was carried out in Central Otago, in which the performance of a minisprinkler-based targeted system was compared with that of the conventionally used impact-drive approach. In the targeted system, the minisprinklers were attached to a lateral pipe suspended on an overhead wire. Artificial bud temperature sensors were used to monitor conditions within two treatment areas and at a control site adjacent to the protected areas. Eleven frost events were monitored, spanning the period from tree dormancy to full leaf. It was shown that targeted systems are capable of providing the same levels of protection as their more conventional counterpart, while introducing substantial savings in water volumes used. The targeted system provided a more uniform level of protection throughout the trial sites because, although the range of application rates laid down was similar to that exhibited by the impact-drive system, it was not as spatially diverse. The use of minisprinklers attached directly to, and suspended beneath the overhead lateral pipe has some advantages. However, the possible effects of pipe movement on sprinkler orientation leads to the conclusion that minisprinklers and laterals being supported on separate wires could be a preferable alternative. This approach also has the advantage that sprinklers already on the market could provide acceptable targeting performance. The effects of wind and icing investigated and alternative forms Additional benefits associated with discussed. on targeting performance were of structural support proposed the use of pulsed operation are discussed. It is concluded that the· targeting technique has many attractions for the grower which make it an option which should be considered when frost protection is required.