EVALUATING WATER QUALITY IMPACTS OF RESIDENTIAL FERTILIZER ORDINANCES IN FLORIDA

Residential fertilizer ordinances at the county-scale have become common across the state of Florida to reduce excessive nutrient loading to waterways and mitigate harmful algal blooms. However, the effectiveness of these ordinances at improving water quality has rarely been analyzed. This study: (1) compiles the fertilizer ordinances throughout the state, (2) temporally aligns water quality data of inland water bodies, and (3) analyzes changes in water quality metrics using regression modeling. Specifically, this study analyzes how water quality changed between periods before, during, and after ordinances were implemented within each county using data collected by the community-science Florida Lakewatch program. As of 2020, thirty-two counties have a fertilizer ordinance which typically include a summer or winter ban on fertilizer use. Using counties with no ordinance as the control, preliminary results in total phosphorus show there is no meaningful difference in trends when compared to counties that do have an adopted ordinance. Further analyses will explore total nitrogen, chlorophyll, and turbidity to conclude the effectiveness of the ordinances. Results of this study can be used to better inform water policy and fertilizer ordinances throughout the state.