A SUMMARY OF LANDOWNER SURVEYS AND WATER QUALITY DATA FROM THE NORTHERN LAKE OKEECHOBEE WATERSHED

Abstract

In the last 25 years, Lake Okeechobee has experienced an accelerated rate of eutrophication due toagricultural practices in the watershed. In response to this problem, a regulatory program was implemented to limit thetotal phosphorus (TP) concentrations in runoff. The TP in runoff from improved pasture areas was limited to 0.35 mg/L.To gain information about typical beef cattle management practices on improved pastures and the impact of thesepractices on water quality, a survey was conducted on ranches in the Lake Okeechobee watershed, and results from otherstudies were examined. Information from this survey indicated that the average stocking rate decreased from 1.25 animalunit/ha (0.51 animal unit/acre) in 1989 to 1.01 animal unit/ha (0.41 animal unit/acre) in 1996. The average stocking ratefor the ranches surveyed for the 8 year period was 1.12 animal unit/ha (0.45 animal unit/acre). Historically, the stockingrates have varied from one animal unit per acre to one animal unit per four acres. The phosphorus fertilization rateranged from 0 kg/ha-yr (0 lb P/acre-yr) to 29.87 kg/ha-yr (26.4 lb P/acre-yr). Ten of the eleven surveyed ranches feedtheir cattle a supplement for a couple months out of the year. The most common supplement type was molasses.Bahiagrass was the most common grass type grown on the ranches. In addition to the survey, water quality data from69 improved pasture sites were analyzed. Although the seven year average TP concentration from the Works of the District(WOD) samples was 0.45 mg/L, and 37 of the 69 sites had period of record averages greater than the limit, 59% of theindividual samples collected were less than the 0.35 mg/L limit. The median of the 2,663 samples collected was 0.29 mg/Land the mode was 0.09 mg/L. This indicates that the ranches have the potential to achieve the WOD limit. Additionalanalyses should be conducted on farms that are meeting the limit. The results could be used to help the ranchers withfarms that are out of compliance determine how to change their management practices to meet the limit.