Effects of Selected Wetting Agents on Removing Organic Coating from Water Repellent USGA Sand.

Soil hydrophobicity, which causes localized dry spot (LDS), is a common problem for golf courses, especially for creeping bentgrass growing on sand-based growing media such as United States Golf Association (USGA) greens. Water-repellency is caused by layers of organic substances, also referred as humic substances that build up on the surface of sand particles. Wetting agents, amphiphilic molecules that contain both water-loving and oil-loving groups, are the primary tool for alleviation of water-repellency. In addition to improving soil water retentions, certain commercialized wetting agents claim that these products contain organic solvent and can actually remove the humic substances from the sand surface. No research-based information, however, has been generated regarding the potential and efficacy of those compounds. At the University of Missouri, a laboratory-based experiment was carried out to evaluate the effect of single application of selected wetting agents for their potentials of removing organic coatings from hydrophobic sand. Hydrophobic sand was collected from a USGA green where naturally occurred hydrophobicity has been documented. After homogenization, the hydrophobicity of the collected sand was determined to be strong, based on a molarity of ethanol droplet (MED) test which resulted in an average of 2.1 molar. Sand was then packed uniformly into soil columns made of PVC pipes, before subjected to a single application of selected wetting agents at label suggested rates, including Matador, OARS, and pHAcid in 70 ml application volume, in addition to a water-only control. Treatments were arranged in a completely randomized design with 3 replications, and the entire experiment was repeated once. Immediately after treatment application, sand columns treated with OARS or Matador resulted in <2 ml of leachate, compared to 12 or 16 ml of leachates from pHAcid- and water-treated columns, respectively. After 24 hours, all soil columns were flushed with water at pre-determined pore volumes for 3 times. Leachates collected from these 3 wash events, and the leachates immediately after treatment applications were subjected to dissolved/particulate organic carbon (DOC/POC) analysis. Soil columns receiving water-only treatment resulted in 70 mg of DOC that were flushed out from the hydrophobic sand columns. In comparison, no statistic difference was found in DOC collected from pHAcid-treated columns. However, soil columns treated with Matador or ORAS both showed net decreases of organic carbon in leachates, after factoring the amount of organic carbons that were introduced by these wetting agents. This result indicates the absorption/adsorption of wetting agent molecules to the hydrophobic sand particles. This experiment is ongoing and more details on POC and hydrophobicity after treatment application will be discussed in the presentation.