What is the ordinance?

In 2021, Miami-Dade County joined other municipalities in our state by enacting a fertilizer ordinance. This ordinance prohibits the use of any fertilizers containing nitrogen and phosphorus from being applied during the rainy season, which takes place every year from May 15-October 31.

Why do we have an ordinance?

The rainy season brings higher levels of surface and groundwater and results in large pulses of added nutrients into Biscayne Bay.

Long-term water quality and seagrass monitoring data show increased nutrient loading into Biscayne Bay over the course over the last few decades. The term “nutrient” can be misleading-after all, as people, we are taught that we need nutrients to become strong and healthy. However, too much of something can actually have a negative effect and become a contaminant. In the case of Biscayne Bay, human development and pollution have changed the composition of the Bay from “oligotrophic,” or low-nutrient, to a more “eutrophic,” or nutrient-laden system.

Over time, nutrients from nitrogen and phosphorus have tipped the balance of the Bay’s health. This has been evident in numerous algal blooms proliferating since the early 2000’s (different types of algae in all three regions of the Bay) (Millette et al. 2019, NOAA 2019), and more recently, the 2020 fish kill event that culminated in the loss of hundreds of thousands of bony fish and stingrays. Additionally, the 2022 Biscayne Bay report card, compiled by Miami-Dade County’s Division of Environmental Resource Management shows the water quality of the Bay to be in serious peril.

What does the fertilizer ordinance mean?

This fertilizer ordinance is geared towards residential application of fertilizer. Commercial operations (agriculture, livestock, golf courses and other food production) must comply with other regulations for their respective industry. The purpose of the ordinance is to prevent excess nutrients from entering the Biscayne Bay watershed. The most important component of the ordinance involves not applying fertilizer during the rainy season, but also has other general criteria:

• Do not use phosphorus containing fertilizer unless a soil test determines that it is actually needed
• Limit the amount of nitrogen you apply at any one time or during the year
• Manage yard clippings to prevent them from affecting streets, sidewalks, stormwater drainage systems or water bodies
• If you apply fertilizers as part of your job, get trained on the best management practices that help protect water resources.
• Contact the UF/IFAS Extension Miami-Dade Florida Yards and Neighborhoods Program to learn more about best practices that you can employ in your own home landscape to limit your use of fertilizer application but also save water!

By abiding by the conditions of the ordinance, we can do our part to ensure the long-term health of Biscayne Bay.

 References:

Millette, N., Kelble, C., Linhoss, A., Ashby, S., Visser, L. 2019. Using Spatial Variability in the Rate of Change of Chlorophyll a to Improve Water Quality Management in a Subtropical Oligotrophic Estuary. Estuaries & Coasts 42: 1792-1803.

National Oceanic & Atmospheric Administration (NOAA). 2019. 2015-2020 Biscayne Bay Habitat Focus Area Implementation Plan (updated April 4, 2019). 50pp.

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