| Water conservation is an important need of the turfgrass industry. Two studies were undertaken to examine irrigation scheduling techniques for Kentucky bluegrass (Poa pratensis L.) turf and a third study to determine physiological and growth responses of perennial ryegrass (Lolium perenne L.) to drought stress.; Plant canopy temperature, measured with an infrared thermometer, was shown to be a good indicator of drought stress for Kentucky bluegrass turf. Based on this premise, Stress Degree Day (SDD), Crop Water Stress Index (CWSI), and Critical Point Model (CPM) irrigation scheduling indices were developed and evaluated. The SDD, CWSI, and CPM indices required 14, 43 and 114% more water, respectively, than a tensiometer control. There were no significant differences among treatments for shoot density, verdure, total root weight, root distribution or visual quality. There is potential to schedule irrigations based on plant canopy temperatures.; Reference evapotranspiration (ET(,o)) was estimated using a Class A evaporation pan, the modified Jensen-Haise equation and the FAO modified Penman equation and compared to reference evapotranspiration for Kentucky bluegrass. Generally, the FAO modified Penman equation and the Class A evaporation pan overestimated ET(,o) by 5 and 12%, respectively, and the modified Jensen-Haise equation underestimated ET(,o) by 25%. There was wide variation in daily values of crop coefficients (kc). Crop coefficients were greater for the well watered conditions than the slightly stressed conditions. There were differences in crop coefficients due to season and variation from year to year.; Perennial ryegrass was subjected to three irrigation regimes, resulting in well watered, slightly stressed and moderately stressed conditions. Daily water use rates were highest, intermediate, and lowest for well watered, slightly stressed and moderately stressed conditions, respectively. Shoot density, leaf area index, and visual quality were significantly greater under well watered conditions than under moderately stressed conditions with slightly stressed conditions intermediate. During a dry down cycle, in which the soil was allowed to dry to at least -0.50 MPa for all irrigation regimes, there were no significant differences among irrigation regimes for stomatal diffusive resistance, leaf water potential or canopy minus air temperature differential measured daily for seven consecutive days. |
