Golf Course Management

AUG 2014

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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90 GOLF COURSE MANAGEMENT 08.14 tered the leaf (Figure 4). Coated stomata may increase leaf temperature as transpiration is re - duced and could potentially reduce photosyn- thetic effciency as gas exchange is impeded. This partially explains feld and growth cham - ber results where treated turfgrass often had higher leaf surface temperatures and/or re - duced photosynthesis. Conclusion While the idea of applying pigment- containing products to assist in relieving summer heat stress on creeping bentgrass is desirable, results from this research do not consistently support their use in areas such as the hot, humid southeastern United States. After application, these products often provide a temporary visually appeal - ing green color that masks imperfections on the turfgrass surface. In reality, long-term continued application of many of these products may actually have a negative effect on the turfgrass such as increasing surface temperatures and decreasing carbon-diox - ide exchange (photosynthetic effciency). The infuence of these products on win - ter hardiness of hybrid bermudagrass putting greens is still under investigation. As photo - synthetic properties of bermudagrass (a warm- season [C 4 ] turfgrass) are different from those of bentgrass (a cool-season [C 3 ] turfgrass), we cannot assume pigment-containing products have similar effects on bermudagrass based on results obtained through studies of creep - ing bentgrass. Turfgrasses almost always exhibit certain levels of stress, especially when grown outside of native environments. For now, superinten - dents are better served by adhering to tradi- tional practices of proper aerifcation, fertiliza- tion and watering of putting greens. It has also been noticed that extensive use of products containing heavy metals appears to lead to ac - cumulation of these metals in the upper soil surface (Figure 5), raising concerns that over - application of these products may negatively infuence the chemical and physical properties of soils. Further research on both bentgrass and bermudagrass commenced in summer 2013 and is ongoing with a greater selection of products (Table 2). Applications were made every two weeks at current labeled rates with the initial application to bentgrass made on June 24, 2013, and with fnal data collection on Sept. 24. All measurements from the previ - ous feld trial studies were repeated in 2013. Similar treatments were made in fall 2013 to hybrid bermudagrass greens to ascertain win - ter survival following treatment. This experi- ment is ongoing and will be covered in a sub- sequent article. Readers are reminded this research was Figure 3. (left) Confocal microscopy projection image (20×) of Turf Screen on creeping bentgrass leaves with colors indicating a defnitive line between the product (red) and the leaf surface (green). This suggests Turf Screen covers the leaf surface, including stomata, resulting in decreased moisture and gas exchange capacity leading to increased surface temperatures and/or reduced photosynthesis. Photos by J. Gann Figure 4. (below) Confocal microscopy projection image (20×) of PAR on creeping bentgrass leaves. Dispersion of colors indicates PAR (red) actually entered the leaf (green) and may have interfered less with stomatal conductance.

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