Plant Factors for Irrigating Mixed Turfgrass and Shrub Landscapes in a Humid Environment

Abstract

Landscape water conservation methods and techniques contribute to managing water resources. Use of reference evapotranspiration (ETo) data and landscape coefficients is one method that needs further development. Local ETo data and actual plant water use were used to calculate plant factors (PFs) for three model landscapes composed of mixtures of turfgrass and shrubs. Model landscapes using a sandy loam soil included st. augustinegrass (Stenotaphrum secundatum), privet (Ligustrum japonicum), dwarf burford holly (Ilex cornuta ‘Burfordii Nana’), and dwarf yaupon holly (Ilex vomitoria ‘Nana’) at three ratios of turfgrass to shrub vegetative cover: 80:20, 50:50, and 20:80. Soil was placed into inground lysimeters in a complete randomized block design with soil moisture sensors and a drainage system. Lysimeters were irrigated with a sprinkler system, and water was applied at a rate of 100% replacement of ETo minus precipitation. Lysimeter soil leachate was collected from the drainage system and quantified. After 2 years, the PF of 20:80 and 50:50 turfgrass/shrub combination were greater than the PF of the 80:20 combination. Plant factors for the 80:20, 50:50, and 20:80 turfgrass:shrub combinations were 0.68, 0.97, and 1.01, respectively. There were no seasonal differences in PFs. Total growing season leachate depth over 2 years was 63.4, 30.7, and 12.6 mm for 80:20, 50:50, and 20:80, respectively. Further work on PFs should include other plant combinations, and evaluation in other climatic zones.