Transpiration responses of warm-season turfgrass in relation to progressive soil drying

Developing turfgrass with good drought resistant is a major goal in breeding programs when water scarcity is one of the long-term challenges facing the turfgrass industry. It has been shown that plant transpiration does not decline until available soil water drops below a certain threshold. Studying the species and genotypic differences in this threshold may lead to turfgrass that conserve water and retain turfgrass quality during drought. The objective of this study was to characterize and compare the transpiration response of 19 warm-season turfgrass genotypes and cultivars in five species during soil drying and well-watered conditions in the greenhouse. The species included in the study were: Zoysia japonica (Steud), Zoysia matrella L., common bermudagrass (Cynodon dactylon L. Pers. var. dactylon), African bermudagrass (Cynodon transvaalensis Burtt-Davy), hybrid bermudagrass (C. dactylon L. var. dactylon × C. translvaalensis Burtt-Davy) and St. Augustinegrass [Stenotaphrum secundatum (Walter) Kuntze]. They were evaluated for evapotranspiration rate (ET) and the sensitivity of transpiration to soil drying which was indicated by a break point of the fraction transpirable soil water (FTSW). The range of break point during dry down was from 0.25 to 0.41, and genotypes within species had different ET when well-watered (ETck). Break point values were not correlated with the number of days to the endpoint, where ET declined below 10% of the control. Instead, the number of days to endpoint was negatively correlated with ETck (−0.59, P ≤ 0.01). Thus, these results found significant variability in turfgrass break point and ETck that could contribute to water conservation, and a better understanding of drought responses in warm season turfgrasses.