|Horticultural frost protection|
Think Water Tasman Bay is nestled in a horticultural oasis. The landscape is covered in apples, pears, kiwifruit, grapes, citrus, nuts, and olives.
Horticulturists fear the damage caused by frosts occurring during bud burst, damaging blossom and reducing fruit development.
|Fighting Frost - The Solution|
One method to fight the frosts aims to cover the vines and delicate buds with a fine mist of water that continually bathes them when temperatures dip to freezing or below.
According to the Alabama Cooperative Extension System, when 1 gram of water freezes, it releases 334 joules of heat. A plant leaf surrounded by water that is freezing will remain at 0 degrees C for as long as the process of freezing is active.
The continuous application of water is crucial. It is the process of freezing that protects the blossoms or fruit. When freezing stops and evaporation starts, the temperature goes down.
The process works well when temperatures are hovering around freezing, but at temperatures around -2 or -3 degrees Celsius, ice forming on the branches of the trees builds up quickly and limb breakage becomes an issue.
Wind also decreases the effectiveness of the process, since it speeds evaporation.
In spring through to late summer the micro irrigation sprinklers are moved from the ground and placed in the air above the vines.
Temperature sensors placed strategically around the block send telemetry alarms to cell phones to alert the owners of high risk of frosts occurring so water can be turned on, either manually or automatically.
Sprinklers are turned on when temperatures fall below 1-2°C and are turned off when temperatures rise enough to melt the icicles.
The potential costs of large crop losses caused by damage to frost sensitive plant tissue are obvious. Our company has been involved in designing and installing several frost-fighting sprinkler systems.
In some cases we have installed an entire system from scratch, in other cases we have added to existing irrigation infrastructure.
In all cases, the sprinklers must be capable of applying water at a rate of 10-12 l/s/ha. Particular attention is given to sprinkler type and spacing so that water is applied evenly. Distribution patterns with a CU (Christiansen Uniformity Coefficient) of at least 84% is recommended.
Growers are urged to maintain and test their systems well before the first frosts are expected to ensure that they are working properly.
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