Performance of Three Warm Season Turfgrasses under Linear Gradient Irrigation

Drought is an environmental stress that will lead to the decline and loss of turfgrass. Most areas of Singapore, require irrigation to maintain desirable turfgrass quality. As water conservation has become an important issue, researchers have put significant effort into developing and evaluating turf species with exceptional drought resistance (Carrow, 1995; Peacock, 2001; Fu et al., 2004; Barton and Colmer, 2006; Huang, 2008). The results from these studies suggest that turfgrasses differ in their performance during drought stress. In a study by Songul et al. (2011), rankings of relative drought resistance under Mediterranean conditions of Turkey indicated that relative drought resistance was superior for Cynodon dactylon x C. transvaalensis (Hybrid green couch), Bouteloua dactyloides (buffalo grass), and Paspalum notatum (bahia grass). Conversely, drought resistance was less ideal for Paspalum vaginatum (seashore paspalum), Eremochloa ophiuroides (centipede grass), Zoysia matrella, and Festuca arundinacea (tall fescue). In another field observation by SeedLand® (LawnGrasses.com), grasses for drought resistance were ranked in the order of Cynodon dactylon x C. transvaalensis, Paspalum notatum, Zoysia matrella, Eremochloa ophiuroides, Festuca spp, and Stenotaphrum secundatum (St. Augustine grass). Noteworthy however, that Morris and Shearman (2007) suggested that variations in the rankings of drought resistance may be a result of the varying climatic conditions of the various sites, the assessment method, and duration of the drought. Zoysia matrella, Stenotaphrum secundatum, and Axonopus compressus (broadleaf carpet grass) are the most commonly used turfgrass species in Singapore, but the use of Cynodon dactylon has increased in recent years because of the ability to tolerate drought. This grass has been used as an alternative to ABSTRACT. The appropriate level of irrigation for turfgrasses is vital to the performance of the turfgrass as well as conservation of water. Linear gradient irrigation system (LGIS) facilitates long-term study of turf performance under continuous irrigation gradients at extreme ends of the irrigation scale. The objectives of this study were to: a) determine the minimum irrigation requirements and relative drought resistance in three warm season turfgrasses; and b) evaluate the medium to long-term effects of irrigation levels on turf persistence, weed invasion, and susceptibility to diseases. Results suggest that grasses differed in drought resistance and persistence under variable irrigation regimes. Irrigation (Ep) required for consistent acceptable turf quality for respective grasses was Cynodon dactylon x C. transvaalensis (61%), Zoysia matrella L. Merr (73%), and Stenotaphrum secundatum ‘Palmetto’ (86%). Brown patch infection was most prevalent in Stenotaphrum secundatum ‘Palmetto’ at 12 and 125% Ep irrigation. Cynodon dactylon x C. transvaalensis and Zoysia matrella L. Merr were better able to adapt to the various irrigation regimes, and this ability allowed these species to resist drought, and maintain turf coverage which in turn, kept weeds and the occurrence of diseases at bay. Ranking these grasses for their drought tolerance abilities showed that Cynodon dactylon x C. transvaalensis had the most outstanding resistance against drought, followed by Zoysia matrella L. Merr, and lastly, Stenotaphrum secundatum ‘Palmetto’. Despite having the highest irrigation requirement, Stenotaphrum secundatum ‘Palmetto’ was still not able to maintain persistence at high irrigation regimes. Likewise, this grass also lost turf coverage at low irrigation levels.