AFEPASA launches a new solution to fight against excessive temperature in crops, adapting them to the constant climate change

Authors: 

• Esther Muries Berenguer - Technical Agricultural Engineer and graduated in Environmental Sciences. Trial Officer and Sales Manager of Southeast Spain at AFEPASA.

• Guillermo Vázquez Fernández - Agronomist. Product Manager, Trials and Development Responsible at AFEPASA.

At AFEPASA we have been working together with farmers so that they can overcome the different problems that have been appearing since our onset in 1893. The company was founded to fight the effects of the appearance of powdery mildew in the Spanish fields from North America, in the mid-19th century. Since then, we have been concerned about the successive problems that have appeared, such as the lack of sulphur in soils, since the end of the 20th century when the polluting sulphones in the atmosphere began to decrease, with the consequent reduction of acid rain, which, despite the environmental problem it entailed, provided a quantity of sulphur as a nutrient to agricultural soils. Since the beginning of the 21st century, AFEPASA has focused on correcting new farmer’s problems, such as excess salinity in soils, produced by low-quality irrigation water, and improving crop conditions, correcting high alkalinity or lack of organic matter.

In recent years, when climate change has become a worrying reality, the difference between seasons has become less and less evident, with soft winters and extremely hot summers. The latest heatwaves experienced in Europe in the last summers of the 2020s and especially 2023, show us that these events are going to be increasingly frequent around the world (Image 1).

Image 1: Monthly global surface temperature anomalies since 1940. (The 2023 Annual Climate Summary. Copernicus Programme)

Especially in the Mediterranean area, temperature anomalies have been the highest in recent decades, leading to periods of +5ºC above normal temperature in the month of July (Image 2) and also occurring in the months of August and September.

Image 2: Surface air temperature anomaly in July 2023, from the average of the years 1991 to 2020 (Image of the day, Copernicus Programme)

Aware that this problem disrupts crop cycles, and significantly damages the quality and quantity of harvests, at AFEPASA we have focused on finding solutions with which farmers can cope with these increasingly hot years. This is the case of SOLDEFEND PLUS, a product designed to be used in foliar spraying, perfectly compatible with those moments when we are approaching maturity and the crop is especially sensitive to any nutritional contribution. The main product composition are two molecules based on Zinc and Calcium, with a special ability to reflect sunlight, and therefore to reduce the temperature in leaves and fruits. 

The direct and most visual damage caused by excess radiation in cultures is superficial burns, which are necrotic spots of dead cells unable to survive in the face of such a large amount of radiation. These spots are gateways to numerous pathogens that can initiate fruit rot and premature death of leaves and stems.

But it is the indirect damage that generates the biggest problem for many farmers, less predictable, but with more impact on harvest quality. Excess heat produces excessive evapotranspiration in the leaves, which leads to dehydration of the plant and consequent drying. And in the case of fruits, a series of physiological and biochemical responses are generated as complex defense mechanisms to minimize damage, such as the generation of photoprotective pigments, secretion of antioxidant enzymes and metabolites, as well as heat shock proteins (HSP). All this set of reactions causes the ripening cycle to vary in an unforeseen way for the farmer, producing unforeseen harvest maduration and changes in the quality parameters of the fruit.

In the case of wine grape production, where the quality parameters are similar, or more important than the yield, damage due to excessive heat generates a serious disorder for winemakers. 

The summer of 2023, in addition to being one of the warmest in last times, has been one that has accumulated the most small rains, which, far from irrigating, add more negative effects on crops (Image 3).

Image 3:  Variation percentage in rainfall during the summer of 2023 in Spain, compared to the average from 1991 to 2020. (AEMET)

It is becoming more and more common that, due to the appearance of summer storms, most of the products applied in previous days wash and lose their effects, forcing the farmer to repeat the applications. And therefore, this is another of the characteristics in which AFEPASA has focused on distinguishing, a specific manufacturing process and a careful choice of formulants, which avoid washing the product in the days following application (Image 4).

Image 4: Detail of product persistence in vineyards in Rioja, Spain; less than an hour after a 20mm rain, 15 days after SOLDEFEND PLUS application. (Authors' own creation) 

At AFEPASA we have carried out numerous trials to verify the efficacy of SOLDEFEND PLUS in crops susceptible to damage by high temperatures and solar radiation. Among them, the successes obtained in the vineyard stand out, where all the tests carried out have shown the high efficacy of this product. Many of the evaluations were carried out using a thermal camera, taking photographs on the surface of the plant that was in the sun, with clear differences between the treated and the controls (Image 5).

Image 5: Example of thermal imaging of untreated bunches (left, control) vs. treated bunches (right- Soldefend plus)

A clear example is the trial carried out in the vineyard in collaboration with the Universitat Rovira i Virgili, in Tarragona. It was a comparison in three different varieties, Cabernet Sauvignon, Grenache and Marselan belonging to Mas de Frares Winery, where the temperature of leaves and bunches was lowered by an average of 5ºC in the 3 varieties during the summer months, with only two applications of the product in mid and late July (Image 6).

Image 6: Bunches and leaves temperatures just before harvest, in 3varieties: Cabernet Sauvignon, Garnacha and Marselan. Check plots in grey, SOLDEFEND treated in yellow. (Authors' own creation)

This decrease in temperature caused a reduction in ripening, which made possible to obtain must with lower degrees and higher acidity, which is very interesting in extreme climatic situations such as those of the Mediterranean seaside, which have been seeing their vines ripen earlier and earlier for years, and consequently, a variation of desired quality parameters.

In addition to all these benefits, vinification of the grapes was also carried out, and a wine tasting panel study was carried out, where tasters had to discriminate if the presence of the product interfered with the taste of the wine, obtaining very clear results, being SOLDEFEND PLUS totally undetectable. This leads to the conclusion that the treatments during this trial, in addition to protecting the grapes, do not interfere with the taste sensations of the final product.

As shown in the tests of this article, SOLDEFEND PLUS achieves complete and long-lasting protection, being a safe product, registered as CE Fertiliser in the European Union, and accepted for use in organic farming. It is an easy-to-handle liquid suspension (SC) that is perfectly stable during storage. Its safety and compatibility with other nutritional or phytosanitary products makes it ideal for inclusion in pre-existing treatment plans, so common in the field to combat summer pests and other nutritional deficiencies. This management is really simple, as it is two applications of 10L/ha in the seasons closest to the forecasts of large heat cycles, with broth volumes of 500 to 1,000L/ha of water.

This article will be published in AgroPages magazine Annual Review 2023.