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Frost fans save grape vines from ‘black frosts’
It is easy to see the effect frost fans had against the reported ‘black frost’ in Padthaway, Australia over the previous weekend. The grape vines within the fan coverage area were a healthy green, whilst all around the vines had been blackened by the sub-zero temperatures.
Kim Lang from Terra Rossa Viticultural Management manages five vineyards between Wrattonbully and Lucindale with seventeen frost fans between them. “Some of the fans ran for three consecutive nights clocking up around 20 hours”, says Lang. He estimates they’d have suffered 70 - 80% loss without them. Over the next few days, growers in Padthaway, Wrattonbully and Coonawarra reported similar stories.
Frost-blackened vines beyond the frost fan’s protective coverage area
“This frost event caught us by surprise so there was no time for those relying on helicopters to make arrangements. The thing with the frost fans nowadays is they’re armed and ready to automatically run when they need to. The water is also marginal up here compared to Coonawarra in terms of availability and quality. Higher levels of salinity can cause leaf burn and moisture deficits even though the soil appears wet, reflected by reduced growth rate, fruit quality and yield. Applying copious amounts of water for frost protection close to harvest also risks wrecking the fruit”, says Lang.
However, some growers still question the efficacy of frost fans and Ben Daking from Australian Frost Fans believes this is partly to do with these events being reported as ‘black frosts’ and the perceptions that creates. A black frost is defined as “a severe freezing that blackens growing plants without a visible frost”.
However, Daking believes the term ‘black frost’ can create connotations with advection frosts where there is little or no inversion layer.
Frost Fans work by utilizing warmer / drier air from the ‘inversion’ layer to create air movement at the fruiting/ flowering height in vineyards on still cold nights preventing damage to flowers, soft tissue and fruit.
Frost fans are an efficient and effective method to protect against frost damage and cold injury during radiation frost events. Radiation frosts only occur at night and are caused by long wave radiation cooling from the earth to the sky. The coldest air is closest to the ground and the temperature increases with height above the ground until the inversion cap is reached. Radiation frosts are the most common type of frost in spring and autumn.
Radiation frosts are far more common than advection frosts, which are caused by a large scale invasion of freezing air from the polar-regions. The temperature decreases with height above the ground and the entire air mass is well below 0°C. Advection frosts are very rare in Australia and large scale active frost protection in horticulture to protect against them is not economically feasible.
Daking continues, “through our remote frost fan monitoring service, we have access to historical and real time information for frost events for every frost fan we monitor in Australia and New Zealand. This includes the strength of the inversion layer recorded through temperature probes at the canopy height and at the top of the frost fan tower.”
“We have some clients who now have several hundred fans providing blanket coverage across their vineyards. They simply wouldn’t keep buying them if their efficacy was in question. We are a specialist business – frost fans is all we do – so our ongoing success is based on the efficacy of our products and the service backup we provide.”
However, what growers are really buying is a form of ‘insurance’ to protect the yield and quality of their crops. Some reports suggest active frost protection systems are expensive so Australian Frost Fans has just built a ROI calculator, which will soon be available online. Growers will be able to use their own numbers to make a more informed decision from a value-based rather than a cost-based perspective. In the majority of cases, the returns are compelling. “In the meantime, growers are welcome to contact us and we can run the numbers for them.”
For more information:
Australian Frost Fans
Tel: +61 4 4811 1384 or +61 1800 797 629
Publication date: 11/16/2017
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