By Carlos Arenes:

New climate control techniques for modern agriculture

The impact of climate change is becoming more and more noticeable. Let us list some of the most recent phenomena: severe autumn frost damaged La Rivera's entire kaki production in the 2017 campaign; polar front damaged stone fruit trees in Murcia and Valencia; irradiation frosts damaged the first citrus buds with the first flowers; high temperatures (over 40 ºC), with low relative humidity, were recorded on 13 May 2015, causing huge volumes of citrus fruits to fall due to dehydration, and leading to a lower production in 2015 and an overproduction in 2016. These problems resulted in ruinous prices. With our technique, we can keep very low temperature frosts under control with a very limited volume of water. With 12 cubic metres per hectare an hour we are able to overcome the impact of temperatures as low as -6º C in the case of avocados and of -7º C in the case of citrus, and even lower ones with other fruit trees.

Engineer Carlos Arenes, in a recent conference on climate change in the 30th anniversary of the technical magazine Phytoma.

Climate change is also the cause of drying problems and lack of juice in early mandarins, caused by cycles of many days with very high temperatures in summer. When the temperature exceeds 30 ºC, the plant closes its stomata so as not to dehydrate, as it loses more water through the leaves than it is able to capture from the soil. If these periods are long and the plant needs water, it takes it from the fruits, but afterwards it is no longer returned, causing the mandarins, whose ripening takes place in summer, to end up dry. Also, colder winter periods lead to a lack of winter nutrition, since the soil temperature remains below 10 °C. This results in the growth of few and weaker buds with a pale colour and leads to a massive fall of fruit in the first development stages.

There is an ever more intense search for new, more profitable crops from more tropical climates, as is the case of avocados in areas of Valencia, Huelva, Cádiz, etc. With Mediterranean climates, and even in areas with low risk of frost, the humidity and temperatures in some stages of the crop's growth cause massive falls of fruit, making it difficult for the activity to be profitable.

Climate change is also facilitating the arrival of new pests. For example, there are increasingly more problems with spiders and many of them are caused by the decline of the phytoseiids population, since very low humidity conditions and high temperatures are lethal for them.

Given all these problems, our company, which used to be just a producer of citrus and a variety of stone fruit trees, thought that a solution was needed. The focus would first be on the cold, since the losses cause by it are huge every year, but worst of all is the loss of our market share. We studied all the anti-freeze systems that were being used in the world and we realised that water was the most effective in terms of efficiency and costs, but great volumes of water needed to be used. We tested it, looked into all its drawbacks and we studied why they were used. Everything started with Jesuit monks some 300 years ago. They said that each hectare of soil loses between 500,000 and 1,500,000 calories per hour due to irradiation, and they thought that if every gram of water we freeze released 80 calories, the solution was clear: for each degree that the temperature drops, 1 mm of water per square metre should be applied. For a -5 ºC frost, 5 mm of water should thus be sufficient.

The system works, so no further developments were made until our days. However, after hundreds of tests and studies, we realised that if water was constantly applied, without rotations and with very high flow diffusers, with 400% overlaps and uniformity coefficients exceeding 90%, making sure that only a limited volume of water was applied, we could keep the impact of very low temperature frosts under control with a very limited amount of water (the one available for irrigation). With 12 cubic metres per hectare and hour we are able to prevent the impact of -6 ºC frosts in avocados or of -7 ºC ones in citrus fruits.

What our technique does is saturate the atmosphere with humidity in a constant way, because an atmosphere saturated with humidity doesn't conduct heat as easily, so the soil's heat is not lost by irradiation and the cold does not penetrate it. Outside of the plot, we could have -6 ºC, and inside it we will have -1.7 ºC, and the crop, protected by the ice, will remain at 0 ºC, which is the temperature of wet ice. The low volume of water need makes this system ideal for evergreen crops, such as citrus, avocados, blackberries, blueberries, etc.

Once the issues with the cold were solved, our next challenge was to prevent our crops from suffering damage in periods of fruit setting or full summer. We designed some diffusers that apply water on the crops themselves, with a specific drop size and radius for each crop, so that each gram of water evaporated absorbs 580 calories. If we apply 12 cubic metres, which is 12,000 litres and 12,000,000 grams of water, and evaporate them, we absorb 7,000,000,000 calories and bring the crop's temperature down from 40 ºC to 24 ºC in the sun and to 27ºC in the shade, since the main evaporation factor is the sun, followed by wind. And most importantly, the much feared magnifying effect is avoided. This happens when some low-flow diffusers saturate the crop with moisture, not allowing the water to evaporate instantly, which burns the leaf and fruit with spots, making the fruit lose its commercial value.

With the same technique, we managed to fully prevent the mandarin drying problem, which is caused by high temperatures and low humidity. In some early mandarin areas, which in August are already internally in perfect condition, but externally green, since a thermal differential is needed for the colour to change, short water pulses at night ensure the plant's temperature stays below 18 ºC. With this, we get that colour we really want. The same system is the basis for a technique to provide aerial nutrition during the entire cycle, but especially in periods with low temperatures, when the plants lack nourishment. The results are spectacular, with a very efficient fruit setting and very high quality productions.

Our range of new products in 2018 includes equipment able to change the plant's temperature and the atmosphere at our convenience and, as always, with very low working pressures, since our system works by speed and not by pressure. You can get to know more about our work in different parts of the world and with various crops, both faced with cold and heat, in our social media pages and our website (

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