Why we use wetting agents on golf greens...

I will be applying the first of roughly six wetting agent applications tomorrow, Wednesday May 9. Many of you may wonder what a wetting agent is and what it does for the greens.

To understand how wetting agents work, it is necessary to know something about the three forces that affect the movement of water into the soil. The first is gravity; it is a constant force that pulls the water downward. The second is cohesion, the attraction of water molecules for each other. It is the force that holds a droplet of water together. It creates the droplet's surface tension, which causes the droplet to behave as if a thin, flexible film covered its surface, tending to keep the water molecules apart from other substances. The third force is adhesion, the attraction of water molecules to other substances. This force causes water molecules to adhere to other objects, such as soil particles.

In hydrophobic soils, the soil particles are apparently coated with substances that repel water, much like wax. In studies of localized dry spots in turfgrass, the soil particles were found to be coated with a complex organic, acidic material that appeared to be the mycelium (growth structure) of a fungus.

Nonionic surfactants, or surface active wetting agents, reduce the surface tension of water, allowing the water molecules to spread out. When applied to water-repellent soils in high concentrations, surfactants can improve the ability of the water to penetrate the soil surface and thus increase the infiltration rate.

Source:
Sunderman, H. D. 1983. Soil Wetting Agents, North Central Regional Extension Publication 190. Colby, Kan.: Kansas State University, 4 pp.