Volume 2, Issue 10 (November 2005)
Improving the Infiltration of Water through Repellent Soils Using Synergistic Surfactant Blends Based on Alkyl Glucosides and Ethylene Oxide-Propylene Oxide Block Copolymers
Soil water repellency arises as a consequence of initial soil water content and the type of organic matter incorporated into or adsorbed onto the individual soil particles. Water repellent soils create significant agronomic and hydrologic challenges, retarding water infiltration into the soil profile and often rendering entire areas impervious to water penetration. These soils often prevent effective wetting of the rootzone during precipitation or irrigation and lead to increased runoff and leaching of pesticides, fertilizers, and other amendments. Agriculturalists have approached the soil water repellency problem through the use of wetting agent surfactant compositions. The degree of wetting efficacy among surfactant chemistries and formulations has varied significantly. The wetting characteristics of alkyl glucosides and ethylene oxide-propylene block copolymers, two nonionic surfactant classes, were evaluated in the context of improving the infiltration of water through water repellent soil profiles. A laboratory column test was used to measure the initial effectiveness of the wetting agent compositions on synthetically hydrophobized and naturally water repellent soils. A synergistically enhanced wetting rate occurred when the alkyl glucoside to block copolymer ratio was from approximately 6:1 to 0.5:1 by weight, ideally when the ratio was from approximately 4:1 to 0.7:1. Within these ratios, synergism was inversely proportional to the HLB and proportional to the molecular weight of the block copolymer used. This research is the first to demonstrate the promising effects of formulations comprising alkyl glucosides and EO/PO block copolymers on improving the distribution and dynamics of water in repellent soils.