Surfactants II. Definition

A wetting agent is any compound that facilitates a liquid, in our case irrigation water, to penetrate more easily into the soil surface, through a decrease of the surface tension of the liquid and the attraction of the water to the solid particles through mechanisms of these compounds such as polar attraction.

There are many different modes of action of surfactants and, therefore, in order to make the right choice, their mechanisms of action must be understood. Thus, there are different surfactants or surfactant agents (wetting agents):

1.-AnionicThey are negatively charged. Generally they wet quickly, but depending on the application rate, they can be phytotoxic. In addition, due to the negative charges, they can cause dispersion of clays, thus de-structuring fine-textured soils.

2.-Non-ionic:

• POE, Polyoxyethyleneamine surfactants: these are "old chemistry", a mixture of long-chain alkylamines (such as anionic surfactants, which can be phytotoxic in certain situations). They also occur as coadjuvants to herbicides, as in the case of glyphosate, in a way that helps the distribution and penetration of the herbicide throughout the leaf, increasing its uptake by the plant. (Source: Pesticide Action Network on Pesticides and Alternatives for Latin America (RAP-AL). April 2007)
• Block Polymer Surfactants: these are the most recommended for our sports surfaces. They have no phytotoxicity problems and are also very effective in reducing hydrophobicity and increasing VWC. Two types of blocks are presented:

a) Penetrants, straight-chain: with one half hydrophobic and one half hydrophilic. Moves water downward in the soil profileIt is therefore recommended in the washing of salts and/or in combination with calcium source inputs for its cation exchange with Sodium (to be applied in cases of the presence of black layers).

b) Moisturisers: consist of a chain of linear molecules. Water is chain-locked.

Keeps water in the soil profile, interesting in soils with low water holding capacity.

c) Moisturiser blends: possibly more effective in correcting "dryness" as well as improving overall quality.

• Natural surfactants: combination of sugar molecules and acids. They can reduce water repellency. When mixed with wetting and penetrating agents, they create a special synergism, producing greater infiltration than any wetting agent alone.

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• Humic: with a composition that allows water to penetrate through the soil by disrupting the hydrophobic humic structures, prevalent in the upper soil profile (1 to 2 cm), leading to "dryness" or "dryness".dry spots“.
• Multi-branch surfactants: polymers of higher molecular weight and multiple sites of action, each branch is itself a wetting agent.

3.- Cationic: not generally used as surfactants due to their strong biocidal character. They are disinfectants and can be very aggressive towards plant tissues. They are not used in our industry.

"The best ways of wetting hydrophobic areas are to carry out prior work in the area. aerationapply the surfactants and water the area, without letting it dry. "

In summary, there are many different surfactants, but by knowing the strengths and weaknesses of each one we can make optimal use of them. Ask your distributor about the mechanism or type of surfactant he is offering to get the most out of them.

POGO Pro + | Advanced monitoring of sports and agricultural surfaces

You can use instruments to find the dry spots in your field and act on them:

• TDR 350

• POGO Sensor

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