Study shows fertilizer ordinances improve water quality (but timing matters)

GAINESVILLE – A new University of Florida study has found that local residential fertilizer ordinances help improve water quality in nearby lakes, but the timing of fertilizer restrictions influences how effective they are.

Using 30 years of water quality data gathered by the UF/IFAS LAKEWATCH program from 1987 to 2018, scientists found that lakes in areas with winter fertilizer bans had the most improvement over time in levels of nitrogen and phosphorus, the main nutrients found in fertilizers.

These lakes also showed larger increases in water clarity and decreases in chlorophyll since the implementation of fertilizer bans. These measurements can also indicate lower nutrient levels, as excess nutrients can feed algae blooms that lead to turbid waters with higher levels of chlorophyll.

“To date, this is the most comprehensive study of fertilizer ordinances’ impact on water quality, not just in Florida but also nationally, and it would not have been possible without the efforts of our LAKEWATCH community scientists,” said Sam Smidt, an assistant professor in the UF/IFAS department of soil, water and ecosystem sciences and the senior author of the study.