IMPACTS OF RESIDENTIAL FERTILIZER ORDINANCES ON FLORIDA LACUSTRINE WATER QUALITY

Residential fertilizer ordinances designed to limit nutrient loading to aquatic and marine systems have become common across the United States, yet their water quality impacts across space and time largely remain unknown. This study analyzes before and after water quality impacts in lakes throughout the State of Florida relative to county-wide fertilizer ordinances from 1987-2017. We used a linear mixed model to analyze ordinance impacts on total nitrogen, total phosphorous, chlorophyll a, and turbidity. This study further analyzes water quality impacts relative to the type of ordinance (winter fertilizer ban, summer ban, non-seasonal ban, no ban). We found fertilizer bans during the winter season have the greatest impact on improving all water quality parameters, while summer and non-seasonal bans were observed to have marginal improvements. Counties with no ordinance did not observe any improvements in water quality, and increases in phosphorous (i.e., worsened quality) were observed. Results of this study can be used to improve the management of inland and marine waters across other humid tropical and subtropical climate regions, especially those tightly linked to urbanized areas.