Announce risk of polar frosts for next spring
Although at this point it is difficult to establish with certainty what will happen in the coming months in climate, there is a risk that next spring polar frosts such as 2007 and 2013, which affected much of the central area of the country and left millions in losses in the national agricultural sector. That is, at least, the conclusion drawn by Fernando Santibáñez, director of the Center for Agriculture and Environment of the Faculty of Agronomic Sciences of the University of Chile, when analyzing the data delivered these days by the different forecast models with which work
«Based on the information that they provide us, it is valid to think that if the cooling of the Pacific waters occurs starting in June - everything suggests that it will occur - the probabilities of having a spring with more frosts than that of 2015, when the waters were warm»He says.
The specialist explains that, when the waters are colder, the polar masses usually slide more easily over the cold ocean, because the anticyclone moves erratically to the south, serving as a bridge for the masses of Antarctic air.
"In fact, in 2007 and 2013 exactly the same thing happened: we had cold waters and the anticyclone moved, causing those catastrophes that we knew", indicates.
Although all the forecast models agree that the water will go from the current warm phase to a cold one, there is uncertainty regarding what may happen from July onwards. According to Santibáñez, one of the possibilities is that a sudden cooling occurs, beyond half a degree below normal, which could lead to a girl cycle -the cold phase of the El Niño-Southern Oscillation phenomenon ( ENSO), which causes heavy rains to Australia, but deficit of them in Chile- and generate a complicated panorama for agricultural activity this spring. Another option that models assign equal probability, is that this cooling is kept at the limit of normal (up to half a degree below normal temperature). Even, he says, there are some models that predict that low water temperatures could return to normal by the end of the year, which would have a fleeting girl of just three months.
«In that last case, the situation might not be so catastrophic for agriculture. However, since it cannot be ruled out that there is a Niña, which could bring a very cold spring, all that remains is to be alert to the information that the models reveal.«says the academic.
More frost
One of the facts that has caught the attention of producers in recent times, is that many of the most recent frosts have affected areas that were traditionally outside the scope of these phenomena.
"Indeed, in recent years there have been frosts in certain places such as hills and slopes, which in certain areas had never happened in the last hundred years.", says Fernando Santibáñez.
This phenomenon is related to the greater incidence in recent years of polar frosts, which cause cold air to fall to the surface from a distance of 2-4.000 meters high, canceling the benign effect that the hills or hillsides can provide to the orchards.
Experts suspect that these situations are a clear indication that climate change is here to stay. In fact, Fernando Santibáñez argues that in this scenario the anticyclones are moving more frequently towards sub-Antarctic sectors, so these events should occur more frequently in the coming years, especially in the central valley, from the Metropolitan Region to the Maule
«In fact, in most of the central valley, in recent years, there has been a slight increase in the number and intensity of frosts. On the contrary, towards the foothills, the number of frosts has decreased. In the high areas of the mountain range, for its part, there have been fewer frosts than in the past. From the Pan-American Highway to the coast, meanwhile, frosts have increased and this is consistently shown by the climate data of the last 30 years., indicates Santibáñez.
The way to follow
As in recent years have increased frost events in the main agricultural areas of the country, so has the supply of tools that the market has made available to producers to combat them. An aspect that at first sight could seem positive for the sector, but that in fact worries the experts, because there is a high risk that producers are victims of marketing and end up acquiring technologies, whose meager benefits are far from being related to its high cost.
In fact, at present, the recommendations of the experts point to using only two active methodologies: sprinkler irrigation, either by wetting the plants during the event or by applying water on the surface at ground level with micro-sprinklers; and the wind, through the use of towers with propellers, whose action allows to prevent the formation of thermal inversion and prevent cold air from stagnating in the lower part of the orchard.
In Europe and the United States, for example, the combination of both systems is usually used, by simultaneously applying top wind and ground level water with low sprinklers, which do not wet the plant. Thus, in addition to preventing the thermal inversion from forming, an environment with a very high relative humidity is created in the air, which helps to prevent the damage of freezing temperatures in the garden.
In relation to the heat generating machines, Fernando Santibáñez is emphatic in pointing out that there is abundant national and foreign experience that indicates that they do not serve on their own to combat frost, but that they should be used to support the management of wind blades.
«Betting only on this alternative as a weapon to combat frost is a mistake. It's like taking the wrong medicine: not only will I be spending money on the medicine, but I will also not get better from the problem., Explica.
The reason? The hot air emanated by the machines, at more than 100 ° C, is extremely light and goes up very fast - in 20 seconds it is at 10 meters of height-, so it does not reach to be distributed by the surface of the orchard. However, if used in conjunction with the propellers it could help to raise the temperature of the area to be protected.
The other alternatives
But the alternatives for the producers do not end there. Currently there are some application products that do not completely avoid the effect of frost on the fruit, but they do reduce the damage. These are substances that lower the freezing point of tissue and increase the degree of resistance of these to freezing.
«There are not many products of this type that have been successful. In fact, they are super few. For this reason, it is important that farmers do not arrive and buy, but rather that they first inform themselves. The idea is that they purchase products with support, from serious brands.", indicates Santibáñez.
Source: Revista del Campo
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