Low temperatures and freezing conditions present a great threat to crop growth and could result in partial or total losses if not handled appropriately.
Overhead irrigation can provide the highest level of protection when compared to a vast majority of currently available systems. It is also one of the most economical frost control alternatives.
The sprinkler system’s energy consumption is considerably less than what growers normally would spend with heaters and other electrical equipment. The labor requirements are less when compared to these other methods and it is relatively non-polluting.
Frost protection depends on the principal of heat fusion to maintain plant temperature at or near 32˚ F (0˚ C). Essentially, as the air temperature surrounding the plants drops below freezing levels, the water begins to freeze and crystalize, releasing approximately 80 calories of heat for every 0.03 ounces (1 gram) of water that freezes. As the ice encases the plant it partially insulates it from the harsh exterior temperatures. Sprinklers provide a 2 to 5-degree temperature difference, which is just enough to protect the plants.
As long as water is constantly wetting the plant, the system should successfully protect them from severe damage. The ice should appear relatively clear. If there is a clear liquid-ice mixture coating the plants and water is dripping off the ice, then the application rate is sufficient to prevent damage. If the water freezes and has a milky white appearance, then the application rate is too low for the weather conditions.* Thus, the water application must be much more uniform than required for irrigation so that no area receives less than the designated amount.
Wobblers gently apply a consistent and uniform layer of water over plants to keep them covered in ice at all times. This prevents sudden loss of heat. The droplets produced by these sprinklers are consistently sized and large enough to resist wind drift – thereby preserving the pattern’s integrity – but gentle enough to prevent damage to plants. Their constant rotary action also prevents ice buildup and prevents the sprinkler from freezing. In addition, less water is needed for achieving an equal result when compared to stream-driven devices.
** Source: The ABC’s of Frost Management by Robert G. Evans (2008) * For best results, Senninger recommends the use of weather tools, such as psychrometers. Weather tools can alert orchard managers of upcoming frost events and help managers better prepare.
**This document is intended only as a reference tool for typical application considerations and may not apply to all systems or conditions. The information is supplied upon the condition that the persons receiving same will make their own determination as to its suitability for their purposes prior to use. In no event will Senninger Irrigation Inc. be responsible for damages of any nature whatsoever resulting from the use of or reliance upon information from this document or the products to which the information refers.