Understanding light: A resource for turfgrass management

Light is a resource for plant growth. The absence of direct solar radiation creates a shade environment detrimental to plant health. Reductions in light quantity and changes in light quality are important components of such an environment. The purpose of these studies was (1) to elucidate the light quantity and light quality available for turfgrass growth in various types of shade and to compare them to characteristics of full sun; (2) to study the quality of creeping bentgrass turf exposed to shade during the morning compared to creeping bentgrass turf exposed to shade in the afternoon. A spectroradiometer was used to scan the solar spectrum between 300 and 850 nm wavelength in deciduous, coniferous, and building shade and in full sun. Scans were made in 5 nm increments on an hourly basis from 7:30 AM to 7:30 PM, bi-weekly, from the vernal equinox to the autumnal equinox at The Ohio State University Turfgrass Research Center. Scans were also made in the shade of industrial shade cloth and compared to other shade environments. Semi-permanent shade structures were placed on a creeping bentgrass range maintained at a 6.35 mm (1/4 in.) mowing height. Structures were aligned to provide 6 h of morning shade or 6 h of afternoon shade during summer solstice. Each structure was covered with either 80% light reduction cloth or 100% light reduction cloth and each treatment combination was replicated three times. Control treatments of full sun and perpetual shade were also included. No significant difference was found in photosynthetic light quality ((red light + blue light)/green light) among coniferous shade, deciduous shade, and building shade or among tree shades and shade cloth. Significant differences were detected among full sun, tree shade, and building shade, for blue photoreceptor potential (far red light/blue light) and for phytochrome potential (far red light/red light). Results indicated no significant variation among plots receiving morning shade and plots receiving afternoon shade or plots under 80% and 100% shade cloth regardless of response tested. Results of this study provide information useful for the management of turfgrass species in shade. By defining the relationship between trees and turfgrass we are encouraging the use of trees in the landscape while maintaining a healthy environment for turfgrass growth.