The preparation of the mixtures between water and phytosanitary products or fertilizers is a delicate aspect: in some cases thewater plays the important role of solvent, in others it becomes a diluent.
Water acts as a solvent when it allows substances – solid or in any case dense – to dissolve in it: in this way it is possible to sprinkle or nebulize them in the crowns of trees. On the other hand, water becomes a diluent when – in addition to diluting them – it modifies or transforms the original chemical form of the substances introduced. And with crop protection products and fertilizers this last possibility could turn out to be a not so casual aspect, given that both the composition of the water and that of the crop protection product or fertilizer introduced have an impact.
Usually the waters used to create plant protection mixtures or fertilizers – taken directly from canals or aqueducts – have high carbonate contents, which lead them to be alkaline, with values which can exceed the 7,5.
In Italy the waters generally have a pH between alkaline and very alkaline and are defined as hard waters, highly mineralized, therefore, rich in calcium and magnesium carbonates. They become even more alkaline during the summer when concentrations of alkalizing elements such as calcium, magnesium, potassium, silicon and sodium can build up.
It thus happens that phytosanitary products or fertilizers which, due to their composition, would require an acid mixture environment, being in alkaline water would register phenomena of alkaline hydrolysis. Alkaline hydrolysis is a chemical reaction, where groups of negatively charged atoms, which are present in the water, are able to separate or inactivate other positively charged groups, which make up agrochemicals or fertilizers, modifying their composition last. From this reaction, crop protection products or fertilizers are transformed into simpler chemical compounds: at this point they would become unsuitable or useless to perform their original functions. This leads to a loss of activity of the products used, which remain lacking the ability to act against the pathogens to be combated, such as insects and fungi, or to decrease their fertilising capacity.
To measure the pH of water, use the pH meter, an easy-to-use instrument that measures acidity or basicity, provides rapid and repeatable results, has a wide range of models and for every price range. pH values are also given by universal indicator papers, litmus type: they are indicators carried on strips of paper, which change color when they are immersed in acid or basic substances, they are easily available on the market and at limited costs.
Many crop protection products and foliar fertilisers, for example, to carry out their action adequately and be more effective, require a pH of the mix between 5,5-6,5, which improves the absorption of the products themselves and maximizes their activity against pathogens. If you need to use a crop protection product or a fertilizer and it is necessary to lower the pH of the water making it slightly acidic, the products available range from vinegar to citric acid. You can then move on to more complex commercial products.
It is important to bring plant protection products or fertilizers to the plant in the conditions that are most suitable for them, in this way they are absorbed more easily and in a shorter time. The danger is also avoided that their prolonged exposure to the air, to light, to the biological entities present in the cuticles of leaves and branches, could decrease their potential for evaporation or alteration.
It thus becomes important, before using a crop protection product or a fertilizer, to find out carefully about its characteristics and the correct ways of using it, so as to allow it to be fully effective.
AIPO Director
Interregional Association
Olive producers
