Frost protection with over-head irrigation

Kobi Shilo, Chief Agronomist, NaanDanJain

Damage to crops in winter or early spring due to frost conditions has always been a major concern for growers. In most cases, frost damage can be prevented by sprinkling the crops with water during the frost period. Researches carried out by authorities such as the New Zealand Agricultural Engineering Institute, the U.S. department of Commerce and the Volcan Institute in Israel have shown that overhead irrigation systems are one of the most efficient ways to prevent frost damage to sensitive crops.

Frost protection in apple orchard with Flipper Apple tree after frost-protecting irrigation with Flipper
Frost protection in apple orchard
with Flipper
Apple tree after frost-protecting
irrigation with Flipper



Principles of overhead irrigation protection

The principle of this method is based on 3 factors:


This method of protection is continued, until the temperature of the surrounding air has risen above 0º C and all ice formations on the plants have melted.

Key considerations

Successful protection of crops from frost damage using sprinklers depends on three crucial factors:

a. Sprinkler rotation speed

Research has shown that a more consistent plant temperature is maintained with a faster rotating sprinkler. To be considered fast enough, a sprinkler should complete one full revolution in less than 60 seconds. Thirty to forty seconds is ideal.


b. Water application rate

The water volume in relation to area application rate has been found to be one of the most important considerations when designing for frost protection. The application rate is calculated after considering factors such as air temperature, wind speed and humidity levels. (See Table for minimum precipitation rates).

Winds affect evaporation levels as well as application uniformity. Wind conditions result in the need for a higher water application rate, to provide the same degree of protection provided when there is no wind.


c. Uniformity

Effective frost protection also depends on how uniformly the sprinkler distributes the water. Extreme care should be exercised in evaluating sprinkler spacing, operating pressures and wind conditions. The choice of sprinkler should be made carefully. An accepted standard would be where the sprinkler produces a CU equal to or higher than 84% with its DU being equal to or higher than 75%.

For targeted frost protection such as the NaanDan Flipper concept, the guideline is not the CU, but full coverage with a defined minimum precipitation rate.

SUGGESTED MINIMUM APPLICATION RATES
DECIDUOUS FRUIT TREES

Approx. min.
temp. Cº
-3.3 to-3.9 -4.4 to -5.0 -5.3 to -5.8 -5.8 to -6.7 -6.9 to -7.8
Application rate
mm/h
2.5 3.0 3.8 4.6 6.4



Additional considerations

Weight of ice: long periods of frost, and sprinkler protection against it, may result in significant amounts of ice being formed on the plant. The initiation of the set temperature should be generally 2 C (above zero), so that the water will not freeze in the pipes.

Targeted frost protection: the idea of targeted frost protection is to minimize the protected area exactly to the plant canopy. This achieves the use of very low-flow and –pressure systems, reducing costs and saving water.

Product selection
233B: Metal sprinkler for full frost protection
Flipper: targeted for frost-protection targeted mini-sprinkler, this is a unique and most advanced concept for narrow-hedge cultivated crops – vineyards, apples and pears, blueberries, etc.

Conclusions

A sensitive crop may be destroyed by frost in a single night. Use of irrigation systems for protection against frost damage has proved to be effective and efficient. Correct design of the systems is, however, critical and specialized advice should be sought by growers before installation.

Download Flipper Installation Guide (pdf file)


Article tags: climate control, overhead irrigation, frost protection, vineyard