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Lusheng Zeng, Jiayang Liu, Robert N. Carrow, Paul L. Raymer and Qingguo Huang

Organic coatings on sand particles can cause soil water repellency (SWR) where a soil does not spontaneously wet; this leads to challenges in water management and crop production. In laboratory studies, we evaluated a novel approach using direct application of 10 enzymes at three (low, medium, high) dosages to remediate SWR on two sand turfgrass soils in a 3-day incubation study and a second study at high dosage with 1-day incubation. A soil:solution ratio of 1:1 (10 g soil and 10 mL solution) was used and a deionized water control included. For Soil 7, a very strongly hydrophobic soil from a localized dry spot turfgrass area with a water drop penetration time (WDPT) of 7440 seconds (untreated) and 332 to 338 seconds (water-treated), the high dosage rates of laccase, chitinase, and protease at 1 and 3 days incubation resulted in WDPT of less than 60 seconds (i.e., hydrophilic soil). Pectinase exhibited similar results only in the 3-day incubation study. On the strongly hydrophobic Soil 21 (WDPT of 655 seconds untreated; 94 to 133 water-treated) from the dry area of a fairy ring-affected area on a turfgrass site, high dosages of chitinase, laccase, pectinase, and protease reduced WDPT to less than 60 seconds in both studies; and medium dosage rates were also effective for all but protease in the 3-day incubation study. Each of the four most effective enzymes for reducing WDPT, noted previously, demonstrated a significant exponential or logarithmic relationship between decreasing WDPT and increasing enzyme dosage. Further studies in field situations will be required to determine enzyme effectiveness on SWR and water management.

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Sudeep S. Sidhu, Qingguo Huang, Robert N. Carrow and Paul L. Raymer

Accumulation of excessive organic matter as thatch restricts permeability of putting greens and is one of the most difficult problems in turfgrass management. A greenhouse experiment using potted bentgrass (Agrostis stolonifera L.) determined the efficacy of a ligninolytic enzyme, laccase, in reducing organic matter accumulation in the thatch-mat layer. Laccase was added biweekly at 0, 0.206, 2.06, and 20.6 units of activity/cm2 with and without guaiacol (2-methoxyphenol), a mediator of laccase, and sampling was performed after two and nine months. Parameters investigated included thickness of the organic layer, thatch layer and mat layer, organic matter content, saturated hydraulic conductivity, and lignin content. Organic matter and thatch layer increased between the two sampling dates in all treatments. Laccase was shown to be effective in slowing the rate of accumulation of organic matter and thatch layer. After two months, application of 20.6 units/cm2 of laccase reduced organic layer thickness by 8.7% and extractive-free total lignin content by 8.4% when compared with non-treated control. After nine months, laccase application rates of 2.06 units/cm2 reduced organic matter and thatch layer thickness by 15.6% and 45.0%, respectively, below levels observed in the non-treated control. Applications using 0.206 units/cm2 of laccase were ineffective. Laccase applications had no influence on turf quality. These positive responses suggest laccase treatments could be a non-disruptive option for thatch and/or mat control in bentgrass.

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Sudeep S. Sidhu, Qingguo Huang, Robert N. Carrow and Paul L. Raymer

Organic layer formation in the form of thatch is a major problem in managed turfgrass systems. Biweekly application of laccase enzyme has been well-documented to facilitate the degradation of thatch and reduce the accumulation rate of organic matter in ‘Crenshaw’ creeping bentgrass (Agrostis stolonifera L.). A field experiment involving creeping bentgrass was conducted to evaluate the residual effects on thatch accumulation after ceasing laccase applications. A significant reduction in thatch layer thickness was observed at 6, 12, and 18 months after treatment initiation when laccase was applied at different rates and frequencies. Residual effects of laccase application were observed for thatch layer thickness, but no additional accumulation of thatch was observed 6 months after treatment cessation. At 18 months after treatment initiation, a significant increase in the thatch layer was observed where treatments had been ceased for 12 months, but no thatch accumulation was observed for laccase treatment for a second 6-month period during the second year. This information is critical to turf practitioners when developing laccase application protocols. Limiting laccase applications for a period of 6 months during 1 year was shown to be effective for thatch control.