Landscape Coefficients of Mixed Turf and Woody Plant Landscapes.

Amenity landscape irrigation continues to be an issue of municipal water conservation efforts.  Landscape irrigation based on reference evapotranspiration (ETo) can contribute to significant water use savings.  The objectives of this study were to determine seasonal landscape crop coefficients (K_L) for model landscapes comprised of turfgrass and woody plant combinations. The K_L was determined from the ratio of actual evapotranspiration and a modified Penman equation reference.   The K_L’s were determined for St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kutze in combination with five woody shrubs common to Texas.  Treatment combinations are 20/80, 50/50, and 80/20 ratios of turfgrass/woody plants over the plot surface area.  Treatments were installed in Huntsville Texas on a Falba fine sandy loam (fine, montmorillonitic, thermic Typic Albaqualfs).  Soil was systematically placed into lysimeters containing a drainage system and soil moisture probes. Lysimeters (1586 L) are in-ground in a randomized complete block design with three blocks.  Soil moisture measurements are made at 0 to 20, 20 to 40, and 40 to 60 cm depths.  The K_L is determined after a rainfall or irrigation event for periods of two to five days.  Results for the spring and summer seasons of 2011 will be presented.