Comparison of four warm-season turfgrass species to natural rainfall or supplemental irrigation in a semiarid climate

Increased urban populations and drought conditions strain municipal water supplies, often resulting in activation of water conservation plans. Supplemental irrigation can be eliminated in extreme situations, which diminishes functional and visual benefits of turfgrass landscapes. The objective of this research was to evaluate differential responses of four warm-season turfgrasses receiving supplemental irrigation (subsurface drip) or natural rainfall only in semiarid climate. Celebration bermudagrass [Cynodon dactylon (L.) Pers.] and Legacy buffalograss [Buchloe dactyloides (Nutt.) Engelm.] were sodded in 2014; Jamur Japanese lawngrass (Zoysia japonica Steud.) and Zeon Manilagrass [Zoysia matrella (L.) Merr.] were sodded in 2016. Species were split with mowing treatments at 5 or 9 cm. Limited mowing effects on response variables led to pooling mowing heights for species. Supplemental irrigation supplied 69 and 173 mm of water from July to September in 2017 and 2018, respectively. Volumetric water content (VWC) in the upper 3.8 cm, canopy temperature, normalized difference vegetation index (NDVI), and visual turf quality were recorded weekly. Drought stress symptoms were evident both years. Manilagrass experienced greatest drought stress, which lowered NDVI and turf quality with significant canopy temperature increase in 2017. Bermudagrass maintained lowest canopy temperature with greatest NDVI and turf quality with natural rainfall each year. Supplemental irrigation was required to lower canopy temperature and enhance NDVI and turf quality for other species. Results suggest bermudagrass maintains best functional and aesthetic quality under 123 mm rainfall. Japanese lawngrass and buffalograss improved with supplemental irrigation, but Manilagrass required supplemental irrigation to provide acceptable quality.