Plant Growth Regulator and Soil Surfactants' Effects on Drought and Salinity Stressed Bermudagrass and Seashore Paspalum.

A study was conducted at New Mexico State University in Las Cruces, NM during the summers of 2010 to 2012 to determine bermudagrass (Cynodon dactylon L.) cultivar Princess 77 and seashore paspalum (Paspalum vaginatum Swartz) cultivar Sea Spray treated with either a soil surfactant (Revolution [modified methyl capped block copolymer]) or a plant growth regulator (PGR) (Trinexapac-ethyl [TE]; 4-[cyclopropylhydroxymethylene]-3,5-dioxocyclohexanecarboxylic acid) response to drought stress. Plots were irrigated at 50% reference evapotranspiration for short grass (ETos) with either saline (electrical conductivity [EC] = 2.6 dS m^-1) or potable (0.6 dS m^-1) water from either a sprinkler or subsurface drip irrigation (SDI) system. Normalized Difference Vegetation Index (NDVI), visual quality ratings, chlorophyll a and b, and carotenoids content and Superoxide Dismutase Activity (SOD) in leaves and stolons were all determined monthly to assess response to turf stress. Princess 77 treated with TE showed the highest quality and the highest NDVI (0.655) on 10 out of 15 sampling dates. Positive effects of TE applications were also observed on Sea Spray quality and NDVI. Subsurface drip irrigation resulted in higher quality and NDVI during the third year of the study when compared with sprinkler irrigation. Princess 77 plots treated with TE showed the highest chlorophyll and carotenoids content (15.7 and 6.0 µg g^-1 fresh weight, respectively) and greatest SOD activity in leaves (37.7 units mg proteins^-1). Both grasses under SDI had higher pigment content at the end of the study than sprinkler-irrigated grasses, suggesting that SDI may be more effective than sprinkler under deficit ETos replacement conditions. Further research is needed to investigate if greater drought tolerance of subsurface drip–irrigated turf is the result of increased water-use efficiency due to altered root morphology.