THE ADAPTATION OF STENOTAPHRUM SECUNDATUM (WALT.) KUNTZE AND FESTUCA ARUNDINACEA SCHREB. TO THREE SHADE ENVIRONMENTS AS AFFECTED BY MOWING HEIGHTS

A study was conducted to evaluate the (1) effectiveness of and validity of conducting turfgrass shade adaptation research under saran shade cloth vs. post oak tree shade, (2) shade adaptation mechanisms of Kenwell tall fescue and Texas Common St. Augustinegrass, and (3) effects of cutting height on the shade adaptation of the above species. Five microenvironmental factors and seven turfgrass responses were measured under 0 shade (full sun), saran shade cloth, and post oak tree shade throughout the season from February through November, 1977.; Saran shade cloth failed to produce an environment comparable to the microclimate under post oak tree shade. Photosynthetic irradiance, light quality, air temperatures, and base canopy temperatures were lower under post oak tree shade than under saran shade cloth. Relative humidities and wind velocities under the shade regimes were found to be similar, and had little influence on differential turfgrass responses. Also, the turf under post oak tree shade had the advantage of exposure to sun flecking. Measurements of shoot density, shoot growth, turf cover, and turfgrass quality were significantly higher under post oak tree shade than under saran shade cloth. Tall fescue leaves were shorter and more prostrate under tree shade than under the artificial shade. Furthermore, the shade-month and shade-cutting height interactions were significantly different between saran shade cloth and post oak tree shade.; Both tall fescue and St. Augustinegrass turfs grown in full sun had higher turf cover, turfgrass quality, shoot growth, shoot density, and shoot carbohydrate content and had shorter leaves than when grown under post oak tree shade. St. Augustinegrass tended to grow more upright under post oak tree shade which reduced light interception and caused removal of a greater percentage of leaf area during mowing. This resulted in a slower establishment rate and a weakened turf. Tall fescue leaf orientations were similar under both full sun and post oak tree shade.; The growth responses of tall fescue and St. Augustinegrass were higher in full sun under post oak tree shade due to higher photosynthetic irradiances and net photosynthetic rate in full sun. Tall fescue and St. Augustinegrass have shown adequate shade adaptation because turf cover and turfgrass quality ratings for each of these turfgrasses were not significantly different between full sun and post oak tree shade.; Tall fescue and St. Augustinegrass turfs grown in full sun and post oak tree shade had higher turf cover, turfgrass quality, and shoot growth at the 7.6 cm cutting height than at 3.8 cm. The shoot density of St. Augustinegrass was higher at the 3.8 cm cutting height in both full sun and post oak tree shade. The shoot density of tall fescue growing under post oak tree shade was higher at the 3.8 cm cutting height; whereas in full sun, the shoot density was higher at the 7.6 cm cutting height. The leaves of tall fescue and St. Augustinegrass were longer and more vertical at the 7.6 cm cutting height than at 3.8 cm in both full sun and post oak tree shade.; Base canopy temperatures for tall fescue under post oak tree shade were near optimal (20 C) during most of the growing season; whereas under full sun, base canopy temperatures of tall fescue were in the supraoptimal range during most of the growing season. Close mowing stimulated tillering and increased shoot density of tall fescue under post oak tree shade. Under full sun, however, close mowing apparently reduced the temperature insulation and protection of meristematic tissues. Consequently, under full sun and at supraoptimal growth temperatures, tall fescue had higher shoot densities at the higher mowing height.