Deficit Irrigation of Mixed Landscapes Based on Turfgrass Coverage and ETo

Landscape irrigation can exceed half the water consumption of residential properties.  To reduce this, our research tested two hypotheses.  First, that irrigation frequency based on turfgrass water needs is sufficient for irrigation of woody shrubs and trees within a mixed landscape.  Second, that warm season Stenotaphrum secundatum, St Augustine turfgrass can maintain an aesthetically pleasing appearance at irrigation volumes and frequencies less than predicted by Penman-Monteith  ETo.  Data was collected during the first year after plant establishment from 1 June 2010 to 31 May 2011 from nine drainage lysimeters in Central Florida.  Lysimeters had a surface area of 13 m² each and were greater than 1 m deep.  Each contained two Viburnum odoratissimum, one Magnolia grandiflora ‘D.D. Blanchard’ magnolia, and 9.7 m² of ’Floratam', St. Augustine turfgrass.  Irrigation regimes of 60%, 75% and 90% of ETo were adhered to throughout the year and adjusted for rain events.  Irrigation occurred when cumulative depth of ETo exceeded 1.90 cm.  All magnolias and viburnum hedges displayed aesthetically pleasing quality, independent of deficit irrigation level (DI).  Turfgrass quality varied among DI levels, yet were above the minimum acceptable quality.  Results indicate ‘Floratam’ turfgrass can be irrigated at 60% of ETo equation in Central Florida during a dry year, and still maintain acceptable aesthetic quality.  This frequency also maintained acceptable quality of magnolia trees and a typical woody hedge when concurrently irrigated at 43% ETo based on horizontal projected canopy area.