Estimation of Net Irrigation Requirements for Turfgrasses In Florida.

Florida’s urban landscape water use is expected to grow considerably over the next few decades. Irrigation information will provide urban irrigators guidelines to help users to reduce and conserve water. The objective of our study was to estimate reference evapotranspiration (ET_o) and net irrigation for turfgrasses in SE USA. Daily meteorological data from 1980 through 2009 were used from 10 weather stations in Florida (Jacksonville, Gainesville, Tallahassee, Orlando, Daytona, Tampa, West Palm Beach, Fort Myers, Miami, and Key West) and one in Alabama (Mobile). ET_o was calculated using the ASCE-EWRI standardized equation. Solar radiation was calculated using the Hargreaves-Samani formula and its coefficients were calibrated for each location. A soil water balance equation was used to estimate the net irrigation requirements on a daily basis at each location. Three different sets of monthly crop coefficients for warm-season turfgrasses were used for North, Central and South Florida. Two root zones were tested (20 and 30 cm). 100% turfgrass cover, and 80% irrigation efficiency were assumed. The most dominant soils were considered at each site to determine the available water holding capacity. Preliminary results showed that the annual mean potential evapotranspiration ranged from 1153 mm y^-1 in Tallahassee to 1277 mm y^-1 in Miami. The mean rainfall was variable within the peninsula, with the highest values observed in Miami and Mobile (1651 mm y^-1) and the lowest in Gainesville and Key West (1092 mm y^-1). Estimated mean annual net irrigation ranged from 323 mm y^-1 in Mobile to 759 mm y^-1 in Key West. Tampa and nearby sites showed a value around 508 mm y^-1. Estimated irrigation requirements increased from December through May, decreased during the summer season, and then increased again during September and October. The highest irrigation requirement was estimated in May with approximately 102 mm.