Landscape Coefficients of Mixed Turf and Woody Plant Landscapes.

Irrigation of the landscape environment continues to be an issue of water conservation efforts.  Realization of water savings may be achieved by applying reference evapotranspiration (ET_o) information to irrigation decisions.  The objectives of this study are to 1) determine seasonal landscape crop coefficients (K_L) of mixed turfgrass and woody plant landscapes and 2) determine quantity of leachate per plant treatment combination.  The K_L was determined from the actual evapotranspiration and reference evapotranspiration during multiple dry-down periods in each season.  The K_L’s were determined for St. Augustinegrass Stenotaphrum secundatum (Walt.) Kutze in combination with five woody shrubs common to Texas.  The treatment vegetative combinations were 20/80, 50/50, and 80/20 ratios of turfgrass/woody plant cover over the plot area. Plots were in-ground lysimeters (1586 L) in a randomized complete block design with three blocks.  Treatments were installed on a Falba fine sandy loam (fine, montmorillonitic, thermic Typic Albaqualfs) in Huntsville Texas.  Soil was systematically placed into lysimeters on top of a 5 cm gravel layer containing a pvc pipe drainage system.  Soil moisture probes were placed into the soil, and volumetric water content measured at 0 to 20, 20 to 40, and 40 to 60 cm depths.  The K_L was determined after a rainfall or irrigation event for periods of two to five days.  For the 2012 early-season, the K_L’s were 1.07, 0.99, and 0.67 for 20% turf, 50% turf, and 80% turf, respectively. Results from mid-season and late-season 2012 will be presented.