HIGH PH TREATMENTS AND THE ALLEVIATION OF SOIL HYDROPHOBICITY ON GOLF GREENS

Hydrophobic soil associated with localized dry spots (LDS) on creeping bentgrass (Agrostis palustris Huds.) putting greens has been shown to be caused by a humic and/or fulvic acid coating of the sand particles. Under laboratory conditions, humic acid begins to solubilize at pH 7.0 and is completely soluble at pH 9.5 or greater. The purpose of this study was to determine the potential of high pH treatments for alleviating soil hydrophobicity of a creeping bentgrass golf green. Three separate studies were conducted on the University of Georgia Experimental Golf Green, Athens, GA, during the spring and summer of 1990 and spring of 1991. The creeping bentgrass green, constructed with an 85% sand and 15% peat root zone mixture, had a well documented history of LDS caused by hydrophobic soil. Soil hydrophobicity was determined by the molarity of an aqueous ethanol droplet (MED) technique. Results showed that an application of 0.1 M NaOH sufficient to saturate the upper 50 mm of soil, followed by a water flush of one pore volume, significantly reduced soil hydrophobicity if repeated three or more times. In one study, soil hydrophobicity was completely eliminated after nine consecutive daily treatments of 0.1 M NaOH, each of which was followed by a water flush. A concurrent decrease in soil humic matter content suggested that its dissolution and removal was responsible for the increased wettability of the soil profile. Bentgrass treated with NaOH showed varying degrees of phytotoxicity. The severity of injury depended on the number of consecutive applications and air temperature. Little or no discoloration was noted when air temperatures was less-than-or-equal-to 24-degrees-C; however, severe wilt and desiccation occurred when treatments were applied when air temperature was greater-than-or-equal-to 35-degrees-C. High pH treatments may be an effective means to reduce soil hydrophobicity on sand-based golf putting greens.