The Role of Surfactants in Agricultural Chemicals

The Role of Surfactants in Agricultural Chemicals The agricultural sector has played a crucial role in the economic and social development of our nation since its founding. As the world population grows, agricultural activities and productivity gain global importance with each passing day. With increasing needs and human population, declining arable land area and natural disasters have further increased our responsibility towards the soil. Despite the many resources available today, agricultural production losses and inefficiency of approximately 65% occur due to certain diseases and weeds. For this reason, producers develop different methods to increase productivity in agricultural areas and extend the shelf life of food products. As a chemical solution, the use of agricultural chemicals to increase soil fertility for use in agricultural fields has increased. In order to maximize the yield we obtain from the soil, it is necessary to protect agricultural products from harmful insects, disease-causing organisms and weeds, and to improve product quality and yield. All agricultural chemicals used for this purpose are defined as pesticides. For pesticides to serve their intended benefit, many variables exist. The most important and effective chemicals in agricultural chemical formulations are adjuvants. Adjuvants are chemicals added to formulations or mixtures to obtain, support and complete the benefits expected from agricultural chemicals. Two important effects shown by adjuvants in formulations are; ensuring the physical stability of formulations and increasing chemical activation to create an area of effect on a large surface area. Adjuvants play an important role in soil fertility by increasing biological efficacy through their physical and chemical effects on agricultural chemicals. Adjuvants are classified according to their mechanism of action and adapted to different formulation types and uses.

Surfactants

Surfactants, or "Surface active agents," are the most important functional structures that enable adjuvants to become most effective along with their activation energy. Surfactant substances, due to their different chemical structures, help improve the surface characteristics of the liquid in which they are found by changing surface tension. At the same time, they provide distribution, retention and spreading of formulations, increasing the absorption of the liquid into the surface on which it is located. The change in surface tension occurs through the chemical interaction of two different structures based on a chemical mechanism.

Surface Tension Mechanism

Surface tension is the effort of matter to always reach the most stable and lowest energy level due to thermodynamic optimization. The bonds between molecules on the surface and the water mass below are weaker than their bonds with each other. This is because the hydrogen bonds on the upper surface in contact with air do not bind to air molecules and direct all electromagnetic attraction forces to lateral water molecules. This property causes the water surface to form a flexible layer separate from the rest of the water and at 20°C temperature, provides mechanical tension of 72 dyn/cm². For the components to be included in the system, the Hydrophile-Lipophile Balance (HLB) value of the surfactant to be used should be selected from substances with HLB values close to those of the components. The ratio of the hydrophilic and lipophilic portions of surfactants determines whether a substance is water-loving (hydrophilic) or oil-loving (lipophilic). Generally, HLB value; • Surfactants between 3-6 are water/oil emulsifiers, • Those between 7-9 are wetting agents, • Those between 8-18 are classified as oil/water emulsion makers. However, their work is based on the principle of ensuring regular distribution of medicinal droplets on the plant surface, reducing the contact angle on the plant surface to expand the area and thus creating a large contact area. They increase drug absorption for the purpose of allowing the drug to pass through structures such as hairs and scales on the leaf surface and be absorbed by the plant, and to prevent residue of drug sediment on the plant surface.

Classification of Surfactants According to Ionic Character

Surfactants are named and functionalized according to the functional groups they possess. These are; 1-Nonionic Surfactants Nonionic surfactants are the most compatible and most frequently used group with agricultural chemicals among surfactant groups consisting of uncharged molecules carrying lipophilic and hydrophilic portions. They are widely used as spreading stickers and emulsion aids in plant protection products. Within nonionic surfactants, there is a subgroup called "silicone-based (organosilicon) surfactants." These reduce the surface tension of the mixture more than nonionic surfactants, thereby increasing droplet spreading. It is also known that it increases drug droplet uptake through stomata. As a result of increased droplet spreading and rapid absorption by stomata, organosilicon surfactants accelerate drug surface penetration and absorption, and as a result, they are used even in rainy conditions following agricultural chemical application.   2-Anionic Surfactants Groups carrying negative (-) charge in the active part of the functional structure are called anionic surfactants. Anionic surfactants are also called super-wetting agents due to their spreading and binding properties. These functional structures include aliphatic alcohol sulfates, alkyl benzene sulfonates, lignosulfonates, naphthalene sulfonate formaldehyde, dioctyl and dinonyl sulfosuccinates and phosphate esters. Powerful wetting and dispersing agents used for agricultural productivity are these functional groups. 3-Cationic Surfactants Cationic surfactants, on the other hand, carry positive (+) charge groups in the active part of the functional structure. Derived from ammonia and carrying its antimicrobial properties, they generally have phytotoxic and properties that precipitate in hard water. Because of this property, they show high levels of toxic effects on aquatic organisms.

Auxiliary Adjuvants

Auxiliary adjuvants, although they do not directly affect the physical and chemical properties of formulations, help easier application to the target plant and minimize unwanted effects. While there are auxiliary adjuvants used for different purposes, the most commonly used characteristics in agricultural activities are wetting and dispersing properties. Auxiliary adjuvants used for this purpose are applied in formulations to; - Increase the mixing ratio of powders with water, and make concentrates or suspension concentrates for soluble liquids during processing and production, - Reduce the wetting time of wettable powders and improve water penetration by mixing with water in the spray tank, - Are used for easy wetting of dispersible granules in the spray tank.

Selecting Appropriate Surfactants for Formulations

The ionic structure of surfactants is important for selecting the agricultural chemical to be used together. Anionic surfactants are more effective in contact-acting agricultural chemicals, while nonionic surfactants are more used in systemically-acting agricultural chemicals because they aid penetration of agricultural chemicals into the plant cuticle. Cationic surfactants are not used alone because they are phytotoxic to plants. For example, an Emulsifiable Concentrate (EC) formulation is a pesticide formulation obtained by emulsifying the active ingredient, petroleum solvent and one or more emulsifying surfactants in water. The solvent dissolving the active ingredient does not mix directly with water. The solvent and active ingredient are hydrophobic, meaning they do not like water. For this reason, substances called emulgators are added to enable these substances to mix with water. Here, with our EMULCORE® series products that have achieved optimum Hydrophile-Lipophile Balance, good emulsion and dispersing properties are obtained within the water tank. With products tested according to different temperatures and water hardness levels, a stable and consistent emulsion is obtained. The auxiliary adjuvants developed at our Wonderlab Research and Development Center, approved by the Ministry of Industry and Technology, are used to improve drug and application performance in pesticide applications. In our studies, we aim to improve product quality through technical support we provide to producers in selecting adjuvants suitable for their formulation types, and at the same time, with our innovative perspective, we are taking steps that will change the future of agricultural production. For higher productivity and more effective agriculture, let us together open the doors to new possibilities with extraordinary solutions and meet at Latro for more. Deniz Özge Çolak Agrochemicals Specialist Latro Kimya