2026
Agronomists, seeking to expand the spectrum of action, choose tank mixes. Multi-component products have a certain convenience in use. However, the fixed ratio of active ingredients in such products often does not allow a prompt response to the field's real phytosanitary state.
This was reported in a comment for SuperAgronom.com by Rostyslav Kyryliuk, agri-technology development manager of LNZ Group.
"The alternative is tank mixes of single-component products, the main component of which is water. In modern crop production, increasing attention is paid to the choice of active ingredient, the application rate and the weed development phase. However, in practice one of the key factors of the success of chemical protection is often ignored — the quality of the water used to prepare the working solution," notes the specialist.
A quality, expensive and proven product can lose a significant part of its efficacy even before it gets into the sprayer tank. The reason is an inappropriate pH, high hardness or the presence of impurities in the water. As a result, the farmer sees weak weed control, although the product and the application technology were selected correctly.
"Water is not a 'filler', but an active component of the tank mix. In a typical tank mix, water makes up 95-99% of the volume. It is precisely in it that the active ingredient dissolves, and it is precisely water that first contacts the leaf surface," emphasises Rostyslav Kyryliuk.
Incorrectly selected water can:
- destroy the active ingredient;
- bind pesticide molecules and reduce their availability;
- impair the product's penetration into the plant;
- cause uneven coverage and losses of working solution.
Most natural water sources (wells, rivers, ponds) have a pH of 7.0-8.5, i.e. are neutral or alkaline. For most herbicides the optimal working-solution pH is 5.0-6.5.
"In water with a pH above 7 the process of alkaline hydrolysis occurs — the chemical breakdown of the active ingredient's molecules, as a consequence — part of the product can be destroyed already in the tank, the amount of active ingredient decreases, and the treatment efficacy can drop to 50%. It is important to understand: the problem is not always visually noticeable. The working solution looks normal, but the weeds are only suppressed or regrow after 10-14 days," the expert emphasised.
Hard water is water with an increased content of dissolved mineral salts, primarily calcium (Ca²⁺) and magnesium (Mg²⁺) ions. It is precisely these elements that determine water hardness and affect the work of herbicides and other crop protection products.
Calcium and magnesium ions bind with herbicide molecules and form ineffective complexes, thereby reducing the product's penetration into the plant. In hard water an original product can work worse than a generic in a correctly prepared mix.
"As a consequence we get weak product action, it penetrates the leaf worse and the active ingredient moves more slowly in the plant, and in the field — partial suppression of weeds and the need for a repeat treatment (additional costs)," says Rostyslav Kyryliuk.
Even at the correct pH and normal hardness, water can significantly reduce the action of herbicides due to the presence of various impurities. Often it is precisely this factor that remains overlooked, especially when water from ponds, canals or old wells is used for spraying.
"Mechanical impurities, such as silt, clay and fine dust, most often get into the water from open reservoirs or contaminated tanks. These particles have a large surface and are able to adsorb herbicide molecules onto themselves. As a result, part of the active ingredient is bound already in the tank and in fact does not participate in destroying weeds. Organic impurities, in particular humic substances, plant residues and algae, also actively interact with active ingredients. They not only bind the herbicide but also change the physical properties of the working solution, in particular the surface tension. Because of this the product spreads worse over the leaf surface and penetrates the plant more slowly," the specialist explained.
A separate danger, added Rostyslav Kyryliuk, is posed by iron and manganese impurities, which are often present in well water or appear as a result of the corrosion of metal pipes and tanks. They can enter into chemical reactions with the active ingredients of herbicides, accelerating their oxidation and decomposition.
In addition to the chemical effect, impurities also impair the physical spraying process. Unpurified water contributes to uneven atomisation, an increase in droplet size and clogging of nozzles. As a result, the coverage of the leaf surface is reduced, and even the part of the herbicide that was not bound by impurities reaches the weeds in a smaller amount.
Thus, the efficacy of herbicides depends to a large extent not only on the correctly selected active ingredient, application rate or treatment timing, but also on the quality of the water used to prepare the working solution. Water should be considered a full-fledged element of the crop protection system.
"First of all, it is necessary to determine the pH of the working solution, keeping it within the optimal range for the specific herbicide, usually at the level of a slightly acidic reaction. No less important is to control water hardness by using water conditioners that bind unwanted cations and stabilise the active ingredient. Special attention should be paid to water purity. Mechanical, organic and mineral impurities not only reduce the amount of available herbicide but also impair the spraying quality. That is why water purity and preparation are just as important as the choice of product or observance of the application rate. Quality water allows the active ingredient to fully realise its potential and ensure a predictable and stable result in the field," advises the expert.
