Comparative Performance and Daily Light Integral Requirements of Warm-Season Turfgrasses in Different Seasons

Shade or reduced sunlight poses a major challenge for maintaining acceptable turfgrass quality. The quantification of daily light integral (DLI, mol m(-2) d(-1)) requirement could help to identify shade-tolerant germplasm. The objectives of this study were (i) to compare turf performance, and (ii) to determine seasonal DLI requirement of 12 warm-season turfgrass cultivars in response to varying levels of shade. A greenhouse study that included three experiments was conducted in spring (30/20 degrees C), summer (35/25 degrees C), and winter (25/15 degrees C) months. Shade levels providing 33, 61, and 92% reductions in photosynthetic photo flux were imposed. Twelve cultivars from nine species were evaluated for turfgrass quality (TQ), normalized difference vegetation index, and shoot biomass production over 8 wk. The DLI requirement was obtained through nonlinear regression between DLI and TQ. Most warm-season turfgrass species maintained acceptable TQ up to 33% shade. 'TifGrand' and 'Tifway' bermudagrass [Cynodon dactylon (L.) Pers x C. transvaalensis Burtt-Davy] required each relatively higher DLI ranging from 9.2 (winter) to 21.4 (summer) mol m(-2) d(-1). Zoysiagrass (Zoysia spp.) cultivars maintained acceptable TQ up to 61% shade, with the lowest DLI requirements ranging from 5.9 (winter) to 10.9 (summer) mol m(-2) d(-1). The DLI requirements for the tested grasses were lower in winter (5.9-9.9 mol m(-2) d(-1)) than in spring (9.4-17.4 mol m(-2) d(-1)) and summer (9.9-21.4 mol m(-2) d(-1)). 'Argentine' bahiagrass (Paspalum notatum Flugge) had an increased DLI requirement relative to other entries in summer months.