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Agrochemical adjuvants and their variety

Wednesday, 2019 February 13
Agrochemical adjuvants

Appropriate and well-timed crop protection is essential for agriculture. Every year, new and more efficient plant protection products are created, and it takes a lot of money to develop and purchases it. However, due to various external environmental factors such as rain, wind, heat, prolonged rainfall, dry soil, and water features, the effectiveness of plant protection products is decreasing. Various additives have been developed to control these external threats, changing the physical and chemical properties of the spray feature and ensuring the most effective functions of used pesticides.


These additives are called spray modifiers or adjuvants (the folk expression "sticky substance" or "adhesive"). The term adjuvant comes from the ability of the material to accumulate at the junction of the polar (water) and non-polar (air) phases and to reduce the forces of surface tension.
When spraying solutions, an important PAM indicator is dynamic surface tension. The surface tension of the water is about 72 mN / m. Such a surface tension is enough for a single cent coin on the water surface not to sink, or for a sprayed drop of water to drop off the plant leaf. This is especially visible on plants with a wax layer, such as cabbage. Reducing the surface tension also decreases droplets rebound from the leaf and better moisturizes the surface of the leaf. Additives could significantly affect this water feature while increasing the efficiency of the sprayed working solution.

The benefits of using adjuvants in agriculture are high:

  • reduces the surface tension of the solutions, which ensures that the droplets of the sprayed solution are spread evenly over a thin layer rather than detaching from the leaves of the plant;
  • increases the adherence of droplets of spray solution to the plant;
  • increases penetration through plant leaf hair, effectively floods the plant's stomach, thereby accelerating the penetration of the active substance into the plant;
  • stops sediment formation, improves compatibility of used products;
  • provides rain protection;
  • reduces the amount of pesticides entering the soil;
  • acidifies and softens water;
  • reduces foaming of working spray solutions.

Such additives can reduce or eliminate many of the spraying problems associated with the stability, solubility, incompatibility, foaming, rapid evaporation, degradation, adhesion, etc. of pesticides.
The additive can be chosen in two ways: based on the used pesticide, or on to the desired effect.  When selecting an additive based on the used pesticide, the instructions of it must be read carefully in order to know what condition is needed to ensure its effectiveness (eg. pH of the water used). Also, the additive can be selected according to the external factor - dry or uneven soil surface, high probability of unexpected rainfall during spraying, foaming working solution, or the possibility of delayed harvesting.


Classification of adjuvants


Ethoxylates. This group includes ethoxylated alcohols, nonylphenol ethoxylates, esters. Additives of this group may reduce the surface tension of solutions to 30 mN / m. One of such products is “Lignum”.

 

Organosilicon is an organic compound containing silicon ions. Organosilicon has the highest ability to reduce the surface tension of solutions between all adjuvants. They reduce the tension of the water surface to such a level that the droplets of the spray solution, when applied on the leaf or the top of the plant, can cover several times larger area of the plant. Due to this feature, the use of organosilicon adjuvants requires less water to cover the same vegetation area.
Silicone adjuvant can reduce the surface tension of the solution to 20 mN / m, so the solution can easily penetrate through the leaf stomach. A pesticide with organosilicon adjuvant additives is not washed by the rain, even if it rains after a short time after spraying, because the active pesticide, thanks to adjuvants, enters the plant in less time interval after spraying. “Perifolis” belongs to this product group.


pH buffers. The pH of the solutions has a huge impact on the effectiveness of the pesticide. The pH of the spray solution affects the formation of sediment, which affects the efficiency of the pesticide. The ability to control pH changes in a mixture can be important in preventing the pesticide from degrading to inactive substances caused by alkaline hydrolysis in aqueous solutions. Additives, which affects pH, can improve the dispersion or solubility of the pesticide in the mixture, control its ionic state and increase the compatibility of the mixture. pH buffers are most useful when used in highly alkaline water, which would greatly reduce the activity of the pesticide. Water acidity and softness control product “pH Water Power” with adhesive function and color indicator for acidity.


Special Features Products. Part of the adjuvants is for narrow-range pesticides. For example, soil pesticides need an additive to ensure smooth jaggy and dry soil moistening. Also, larger droplets must be formed, so that they won’t be removed to unwanted areas by wind (product “Periterra”). For contact insecticides and fungicides and additive, which ensures even coverage and also a rapid application of the spray solution to plants and insects, should be used. This function can be performed by a mixture of acrylic and organosilicon, like “Smart Contact”. This product can also be used for another function - sealing of rapeseed pods, thus reducing the self-opening of the pods and yield losses.
Materials stop frothing. The anti-foaming agents reduce or suppress the foaming of the spray solution in the reservoir. They make foam bubbles explode, thus destroying existing foam and preventing new ones (such as “Foamex”)

In conclusion, adjuvants can reduce or eliminate many spraying problems related to the pesticides and fertilizers stability, solubility, incompatibility, foaming, a surface tension of the spray solution, a coating of the plant surface, blowing of droplets, rapid evaporation, degradation, adhesion, and penetration.