Effects of four soil surfactants on four soil-water properties in sand and silt loam

Soil surfactants are wetting agents designed to improve infiltration, water distribution, and water retention. This industry-independent study evaluates the effects on soil-water properties of four surfactants commonly used in the Pacific Northwest: Wet-Sol #233 (Schaeffer), WaterMaxx II (Aquatrols/Western Farm Services), Ad-Sort RST (Simplot), and ADVANTAGE Formula. One (Wilbur-Ellis). These surfactants were tested at labeled rates on two sifted soils with no known water repellency issues: a Warden silt loam and a Quincy sand. No significant differences were found among the means of treatment variables of any of the surfactants or the control (irrigation water only) in the tests of infiltration rate and water holding capacity, at a significance level of alpha = 0.05. Significant differences were found for the tests of unsaturated hydraulic conductivity (p = 0.009) and capillary rise (p = 0.048) in the sand samples only. Lower unsaturated hydraulic conductivity was inferred from the results for Wet-Sol samples compared to the control and all other. samples. Additionally, Formula One performed significantly better than Wet-Sol and Water Maxx in unsaturated hydraulic conductivity, but differences compared to the control were insignificant. In capillary rise tests, the rise height of samples treated with WaterMaxx, Ad-Sorb, and Formula One were significantly lower than that of the control samples. Hence, the use of surfactants did not benefit water penetration or soil-water distribution (up to 24 hours) according to the statistical tests on the four soil physical properties. Furthermore, the surfactants. did not perform consistently across the different experiments. These findings indicate that a single application of these four anionic, nonionic, and block polymer surfactants does not improve the movement and conservation of soil-water in these hydrophilic soils.