In recent weeks it has become clear that sensitivity of agriculture to the dreaded frosts, typical of winter weather conditions. Although it is true that frost is increasingly striking areas that are not accustomed to this type of weather.
On the other hand, and thinking in the short term, the transition from winter to spring is not a smooth and progressive transition, but is characterized by having large temperature fluctuations and sudden changes in weather, which can take us to purely winter weather as soon as they take us to days of almost summery warmth.
The final days of winter and the change of season to spring are among the times of year when atmospheric development is most unpredictable in the short and medium term. The equinoxes, which mark the transition from winter to spring and from summer to autumn, are particularly eventful meteorologically, as during these two periods of the year, atmospheric circulation in mid-latitudes is in the midst of a period of adjustment. In this "struggle" between cold and heat, cold forces enter the south, causing the weather to change abruptly and temporarily impose winter weather.
These sudden changes in weather, with significant rises and falls in temperature, are also common in the months of April, May and even June, which sometimes gives rise to the dreaded late frosts. The already advanced state of the vegetative cycle of the crops, makes the plants already show bare parts very sensitive to low temperatures, unable to withstand a frost of any significance.
Temperature has a direct impact on the biochemical processes of plants.Cold, heat, and temperature fluctuations affect flowers and fruit at different stages of the growth cycle. In winter, trees enter a dormant state. This allows them to withstand low temperatures and develop the buds that will produce flowers and fruit in spring and summer.
When the temperature drops below 0ºC (frost), the environmental condition becomes critical for the development of physiological processes in plants and their tissues, which can be severely damaged by freezing.
The frost They can be classified according to the time in which they occur into: winter, spring or lateWinter frosts affect evergreen fruit trees, while spring frosts affect the same species and deciduous trees that have begun their vegetative development. They can also affect horticultural species, although these, being seasonal plants, may have a certain tolerance if the frost is not excessively severe.
Crops are more sensitive to frost after from the initial development of the buds to the small fruit stage, which is when crops are most sensitive to freezing.
The most dangerous frosts are usually those of irradiation, which occur in spring, a time when vegetative development is important, with the buds already formed and even with the flowers open, this being the most vulnerable moment.
The severity of frost damage to plant tissues depends on several factors, including:
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Age of plants
The new plants, because it has tender tissues, They are more sensitive to frost than adultsFurthermore, the damage can compromise the entire plant, leading to its death. In contrast, in adult plants, only the periphery of the tree is usually burned, leaving it capable of vigorous regrowth from buds located on the shoots in the inner zone.
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Phenological state
Plants whose shoots are actively growing are more susceptible to frost damage.Hence the importance of avoiding late nitrogen fertilization in autumn, especially in new plants, to prevent shoots from developing during the winter period.
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Plantation location
Planting on slopes significantly reduces the risk of frost damage., since cold air is heavier and tends to be located in the lower areas.
Depending on the intensity and duration of the frost, plant damage can range in magnitude, from death to mild leaf burn on the periphery. However, it should be noted that Severe cold causes the loss of production (fruits) of the season and also compromises the production of the following season., by destroying new shoots that could potentially produce fruit.
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Post-management in fruit trees
Once frost has passed, certain cultural practices can accelerate the recovery of the orchard. These include:
- PruningIt is recommended to wait several weeks before pruning dead wood. The extent of the damage should then be assessed. Once the frost risk period has passed, pruning is performed to remove affected shoots and branches.
- Radiation protectionAfter pruning, and considering that one of the effects of frost is severe leaf drop, the trunk and shoots are exposed to sunburn. Protecting them with approved products is recommended.
- Fertilization: It should be started in spring, with shoots measuring 5 to 10 cm. The amount of nitrogen applied will depend on the severity of frost damage. The more severe the frost damage, the less nitrogen should be applied, as the plants will have more shoots and the need for nitrogen will be lower. Furthermore, applications should be spread out as often as possible. Foliar fertilizers can be a good help once sprouting has begun.
- IrrigationIt is not advisable to overwater, as the limited number of leaves prevents normal evapotranspiration. It is recommended to start watering alongside the fertilization program, as long as it hasn't rained. In general, the use of irrigation water and fertilizers should be rational to prevent excessive shoot growth.
- Pests: : the health of the shoots must be taken care of so that they develop without limitations, particularly free from insect or disease attacks.
When frost occurs, there are two methods of work to mitigate economic damage to crops: passive methods, which are carried out before planting and, active methods, which are those that are carried out with the plantation already established.
Passive methods
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Selecting the place to grow
There are places where frost occurs more frequently due to cold air, slope, exposure and soil type. Low areas tend to accumulate cold airThe heat conduction characteristics and storage capacity vary from one soil to another.
Those areas with a higher incidence of frost should not be cultivated with species susceptible to low temperatures.Before making a decision to plant or grow crops in a particular area, farmers should gather information about the occurrence of low temperatures in that area.
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Species selection
There are different degrees of susceptibility to frost between species and varieties.. In addition, some rootstocks confer a certain degree of tolerance to low temperatures. Hence, there are autumn-winter and spring-summer vegetables, or fruit tree varieties with early, mid-, or late flowering (including extra-early and extra-late flowering in some cases).
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Natural movement of cold air
Cold air, being denser, tends to occupy lower positions in a specific area.One possible measure to implement is to facilitate the movement of cold air to lower elevations to prevent temperatures that could cause crop damage.
Active methods
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Use of horizontal axis fans
Its purpose is mix the air which is found between a height of 10 to 20 m on the ground and at a higher temperature, due to the effect of thermal inversion, which contributes to an increase in air temperature in the leaf zone.
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Use of sprinklers
The use of sprinklers is one of the most widely used measures for frost control today. It has the advantage of significantly lower energy consumption than using heaters and large fans. The disadvantage of this system is that it requires an irrigation system specially designed for frost control and can entail a high initial investment cost. Additionally, sufficient water is required to simultaneously irrigate the entire area to be protected.
This system takes advantage of the latent heat of water when it solidifies. When water falls on the plant, it freezes, releasing a certain amount of latent heat that the crop will receive at the place where the drop of water falls..
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Heaters and clouds of smoke
It consists of generating heat through stoves or smoke through fuel boilers that prevent the cooling of the air at the crop level.It is not the most recommended method due to environmental pollution and other ecological issues.
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Padding
These are protective covers placed at the base of the plant, which prevents heat and moisture loss in the soil., protecting the roots. Mulch should be applied before frost sets in, anticipating the low autumn temperatures that are very damaging to crops, since the plants have not yet begun their winter dormancy. This mulch can be natural (plant debris) or synthetic (plastic).
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soil management
A soil free of weeds, dirt or other objects is less susceptible to freezing.This allows more radiation (heat) to be absorbed during the day, which will be released at night.
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Protective covers or nets
It is an element that, when spread as a cover over crops, varies solar radiation and heat. The use of thermal screens achieves production increases of up to 30%, thanks to the ability to manage the heat collected during the day, spread it and maintain it during the night, a period in which temperatures drop.
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Coats and insulators
They can be made of fiberglass or foam rubber, which are excellent heat insulators for plants. They have a moderate lifespan. They also aid rapid regeneration in the event of frost and are relatively inexpensive. One disadvantage is that they can be more difficult to install and handle.
To protect the base of trunks and stems of some plants or fruit trees, it is possible to surround them with flexible materials that act as insulators from the cold.
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Use of nutrients and biostimulants
By using nutritional products or biostimulants, it is possible prepare the plant to better withstand the stress conditions generated by frost, so that the damage caused by it is less and/or to help it better and more quickly overcome the stress suffered and the damage caused.
At Cultifort, we offer a series of recommendations in this regard, which can be used together or alternately, depending on the severity of the frost, the timing of treatment, or the damage caused.
SPIRALIS LONG LIFE and its version ECO They are a first-line treatment alternative. They are a formulation based on organic acids and selected peptide complexes, related to green and red algae, which produce in the plant Structural changes at the level of lignification in its cell wall, increasing the synthesis and accumulation of callose and lignin and offering a physical barrier against abiotic stressIn addition, it produces a cellular response in the plant, activating the synthesis of highly defensive molecules. This would protect the plant from potential pathogen attacks after frost, when it would be most susceptible to these types of physiological disorders.
Another treatment alternative would be the use of CultisilK, a formulation based on silicon and potassium. Silicon provides anatomical changes in the structure of cells, providing mechanical resistance to tissues (among many other beneficial effects), while potassium acts as an osmotic regulator, helping the plant maintain good cell turgor. Both effects combined provide the plant with better conditions and possibilities to withstand abiotic stress conditionsIf you want to know more about the effects of silicon on plants Click here.
We have analyzed two alternatives to prevent possible damage caused by frost but, What if we have already suffered from the frost? In this case, treatments should be focused on strengthening the plant, recovering its vegetative development in a balanced way (without excessive vigor) and, to the extent possible, saving the harvest or what remains of it and/or ensuring or guaranteeing the harvest for the following season.
BVC EVOLUTION (Formerly BVC 2021) It is a biostimulant suitable for these types of situations. Its versatility makes it suitable for any phenological phase, and its formulation is ideal for these situations. Its combination of algae emulsion and amino acids produces the plant's Activation of physiological and metabolic processes, even under adverse conditions, activating chlorophyll synthesis and increasing the rate of photosynthesis and stimulating cell division and the formation of new tissues, among others. BVC EVOLUTION It will induce the beginning of the plant's vegetative activity, stimulate the formation of leaves and flowers, improve the quality of the fruits and increase the plant's resistance to low temperatures and adverse weather conditions.. With BVC EVOLUTION We will also be contributing reducing sugars, which will act as a respiratory substrate, providing energy and facilitating the assimilation of nutrients by the plant.
In conclusion, we can say that it is very important to protect crops from the cold and low temperatures, since apart from the moral damage, the economic loss can be very highWe have seen that there are several methods to mitigate the effects of frost on crops, which can be both preventive and protective. All of these methods will allow us to be prepared and choose the appropriate strategies for any eventuality related to low temperatures.