Look to the Data, Not the Marketing: Turfgrass Research Shows No Differences in ‘Penetrant’ and ‘Retainer’ Wetting Agents
Wetting agents used to counteract hydrophobic sandy soils on putting greens
By John Lovett – Jul. 7, 2025
FAYETTEVILLE, Ark. — After several years of research, the results are in on the difference in turfgrass soil surfactants that are marketed as “penetrants” and “retainers.”
Mike Richardson, professor of horticulture with the Arkansas Agricultural Experiment Station, says putting greens built to United States Golf Association standards with 12-inch-deep sand root zones require meticulous water management to promote both plant health and playability. Among the most important tools for managing water in putting greens are soil surfactants, often called wetting agents.
Despite their critical role in turf maintenance and because they aren’t pest management tools, wetting agents do not go through the same federal registration and labeling process as herbicides, fungicides, or insecticides, resulting in less research data about what they are and how they work. In the absence of such data, marketing terminology such as “penetrant” or “retainer,” along with anecdotal evidence, have been used instead, Richardson explained.
To help clear up the confusion, a study by turfgrass scientists with the experiment station, the research arm of the University of Arkansas System Division of Agriculture, and the Dale Bumpers College of Agricultural, Food and Life Sciences at the University of Arkansas, was recently published by the American Society for Testing and Materials. Co-authors of the study include researchers at Texas Tech University, The Ohio State University and Pennsylvania State University.
The study titled “Penetrants Versus Retainers: Comparing Soil Surfactant Terminology to Performance in Sand-Based Putting Greens” found that differences between soil surfactants marketed as “penetrants” or “retainers” were inconsistent, if present at all. It was published in the ASTM “Pesticide Formulation and Delivery Systems” 43rd Volume.” ASTM stands for Advancing Standards Transforming Markets.
Arkansas Agricultural Experiment Station turfgrass researchers led by Doug Karcher began looking at wetting agent products marketed as “penetrants” and “retainers” in 2017. Karcher, now the horticulture and crop science department chair at The Ohio State University, was assisted by Daniel O’Brien, Ph.D., as a graduate student. O’Brien carried on the work as a Ph.D. student while in Arkansas and served as the lead author of the recently published study. He now works for U.S. Golf Association as a Green Section Research Manager.
The study was supported by the Golf Course Superintendents Association of America.
As part of their investigation, the researchers compared turfgrass soil surfactants marketed as penetrants to those marketed as retainers for their ability to affect rootzone volumetric water content and surface firmness. Volumetric water content, a measurement of how much water a given volume of soil contains, is especially important in sand-based putting greens with their limited water-holding capacity.
Multiple studies were conducted on sand-based putting greens in Fayetteville from 2018 to 2021, and Lubbock, Texas, from 2019 to 2020. The studies included the turfgrass species creeping bentgrass and ultradwarf bermudagrass.
Soil surfactant treatments were applied according to label recommendations and evaluated over a range of rootzone moisture conditions. Volumetric water content was measured at multiple depths using portable moisture meters and surface firmness was assessed through multiple methods.
At the Fayetteville location, during 2018 to 2019, there were no significant differences in volumetric water content between penetrants and retainers on any date or at any depth. In 2021, both penetrants and retainers could produce volumetric water content greater than nontreated controls. Likewise, both product types also resulted in volumetric water content less than nontreated controls. Similar inconsistencies were documented at the Lubbock location.
Collectively, the results reinforced the need to establish soil surfactant classifications based on performance data from field testing rather than marketing terminology, the study concluded.
Co-authors included Joseph Young, associate professor of turfgrass science at Texas Tech University, Michael Fidanza, professor of plant and soil sciences at Pennsylvania State University, and Stanley Kostka, a visiting scholar at PSU.
To learn more about the Division of Agriculture research, visit the Arkansas Agricultural Experiment Station website. Follow us on 𝕏 at @ArkAgResearch, subscribe to the Food, Farms and Forests podcast and sign up for our monthly newsletter, the Arkansas Agricultural Research Report. To learn more about the Division of Agriculture, visit uada.edu. Follow us on 𝕏 at @AgInArk. To learn about extension programs in Arkansas, contact your local Cooperative Extension Service agent or visit uaex.uada.edu.
About the Division of Agriculture
The University of Arkansas System Division of Agriculture’s mission is to strengthen agriculture, communities, and families by connecting trusted research to the adoption of best practices. Through the Agricultural Experiment Station and the Cooperative Extension Service, the Division of Agriculture conducts research and extension work within the nation’s historic land grant education system.
The Division of Agriculture is one of 20 entities within the University of Arkansas System. It has offices in all 75 counties in Arkansas and faculty on three campuses.
Pursuant to 7 CFR § 15.3, the University of Arkansas System Division of Agriculture offers all its Extension and Research programs and services (including employment) without regard to race, color, sex, national origin, religion, age, disability, marital or veteran status, genetic information, sexual preference, pregnancy or any other legally protected status, and is an equal opportunity institution.
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