Currently there are close to 200, if not more, commercially-marketed products making claims of all shapes and sizes, but where do you go to learn what they are really doing? Most decisions are based on advice from a local rep or manufacturer, peer reviews, past experience, or in some cases price and availability. Most of the advice has one take-home message: use wetting agents.
Wetting agents, or surfactants (surface active agents), have been around the industry for decades, and throughout that time, chemistries have evolved. Some will refer to a surfactant as soap. Soaps, however, are anionic surfactants or carry a negative charge which allows them to form bonds with positively charged ions.
Think of soap scum that will form particularly in hard-water scenarios. Soap will form bonds with calcium or magnesium in the water to create an insoluble material that will remain in the tub. Furthermore, these materials are likely to foam, and nobody wants that in their spray tank. Most surfactants used in the T&O world are nonionic, and therefore do not carry any charge. When used properly, they tend to pose very little risk of plant injury.
According to Keith Karnok (UGA retired), in 2004, it was estimated that 87% of Golf Course Superintendents used wetting agents, and that percentage is likely higher today. The reasoning behind the usage was as follows:
- 42% to relieve localized dry spots.
- 32% to help manage water.
- 11% to improve drainage.
- 9% to improve pesticide movement into the soil.
This is consistent with the primary function of a surfactant. These materials are formulated to combat water-repellent soils allowing more water to penetrate the surface and improve lateral movement throughout the rootzone for more uniform wetting. Surfactants also help to reduce the surface tension of water which is held together in droplets very tightly by the forces of cohesion.
Simply put, water forms a very tight droplet strongly repelled by any waxy organic coating on the soil or thatch, and a surfactant will help to spread that droplet out. Visit the Biolin Scientific website for a good visual of that spreading capability.
This function is what helps to improve irrigation efficiency and reduce pressure from localized dry spots. According to Dr. Stan Kostka and Dr. Mike Fidanza, some of the additional marketing claims of surfactants do not to date have scientific research backing them.
What is interesting is the lack in transfer from fine turf to lawn care. Even with over three decades of usage in golf and athletic fields, very few landscape contractors look at adding wetting agents on as a new revenue stream.
Water is the most limiting factor in turf establishment and maintenance of healthy lawns. This is most prevalent in areas like Southern California and Arizona. Inevitably, there are pockets throughout the US and especially on high-value properties where wetting agents could easily become a part of the program. Additionally, those properties with more topography, or windy areas that make irrigation coverage more of a challenge, could try wetting agents for help with soil water distribution.