Influence of Humic Substances on Moisture Retention and Phosphate Absorption of Creeping Bentgrass Putting Greens.
Adam Van Dyke, Paul Johnson, Paul Grossl, and Kelly Kopp. Utah State University, 4820 Old Main Hill, 4820 Old Main Hill, Logan, UT 84322, United States of America
Humic substances reportedly enhance moisture retention of soil and provide other benefits to turfgrass. However, little information is available on specific effects these compounds may have. We are conducting an experiment evaluating the effects of acidic functional groups of humic acid, tannic acid, and citric acid on water holding capacity on a calcareous sand rootzone and phosphate uptake of bentgrass turf. A pilot study was conducted in a greenhouse and irrigated with the organic acid solutions standardized at 250 mg×L-1 C. Irrigation occurred when the volumetric water content reached 5%. Phosphate (KH2PO4) was added midway in the study, and leaf tissue collected at the conclusion. Irrigation intervals were longer for all organic acids compared to the control and soil moisture following irrigation was highest for the humic acid. All organic acid treatments increased tissue phosphorous concentrations, with tannic acid inducing the greatest increase. A more extensive study is underway where individual treatments are irrigated automatically when the volumetric water content reaches 10%. Results thus far have been different from the previous study with the humic acid requiring more frequent irrigation and recording the lowest moisture content following irrigation. This may be due to hydrophobic tendencies of the organic molecules. Field trials with similar treatments are also being conducted at three golf courses.