VoteWater Deep Dive: Get ready for the fight over fertilizer

New study based on flawed past studies could be used to justify permanent ban on fertilizer bans — leading to dirtier water

One of the more dubious actions (and there were plenty) taken by the 2023 Florida Legislature and rubber-stamped by Gov. Ron DeSantis, was a measure snuck into a budget bill that eliminated local governments’ ability to adopt strict fertilizer control ordinances until the 2024 legislative session convenes in January.

The measure authorized $250,000 for University of Florida researchers to review recent studies on fertilizer bans. Specifically, researchers will determine which are more effective: rainy season blackout periods/bans (also called “strong” fertilizer ordinances) or dry season bans.

It seems like a no-brainer: Who thinks applying fertilizer before a typical Florida summer downpour is a good idea? It’s a great way to waste your money as all the nutrients wash off your lawn into your local waterways, where they feed not grass — but harmful algal blooms.

But if the study concludes summertime bans aren’t effective, legislators are expected to seize upon this to preempt local governments from adopting “strong” fertilizer ordinances – and lawmakers could try to scuttle the ones already in place in 18 counties and more than 100 municipalities across the state.

This is shaping up as a battle royale, and if we lose get ready for even dirtier water,

‘Tis the season

Reseachers from the University of Florida’s Institute for Food and Agricultural Sciences, or IFAS, will consider the argument behind summer rainy season fertilizer bans:

  • Frequent, heavy rains during the summer can wash fertilizer applied to lawns and agriculture fields into adjacent ditches and creeks, and from there to larger water bodies like lakes, rivers and lagoons. Once there, nutrients in the fertilizer, particularly nitrogen and phosphorus, feed algal blooms that can devastate ecosystems, cause health problems for humans and animals and wreak havoc on waterfront economies.

Here’s the argument behind winter dry season bans adopted by a handful of municipalities:

  • During the summer plants are growing and absorbing that fertilizer, keeping it out of waterways. During the winter, plants tend to be less active or even dormant, so they don’t always absorb the fertilizer, allowing heavy rains to wash into nearby water bodies.

At first blush there are a couple of problems with the dry season argument.

First, the heavy rains that wash away fertilizer are far more likely to happen during the summer (That’s why we Floridians call it the “rainy season.”) than in the winter (aka the “dry season”).

Even the Florida Yards and Neighborhoods Handbook, published since 1994 by UF/IFAS (the same folks tasked with studying the bans) and the Florida Department of Environmental Protection, makes the argument in favor of summer fertilizer bans.

The most recent edition of the handbook states: “Avoid fertilizing before a significant rainfall (greater than 1 inch). If significant rain is forecast, hold off on applying fertilizer. Rain can wash fertilizer off lawns or cause it to leach into groundwater, contributing to pollution.”

The handbook also suggests trying fertilizers with iron for yellow grass in the summer “before you consider applying a nitrogen fertilizer.”

The reason isn’t specified, but it’s no doubt to avoid nitrogen runoff.

Second, if the reason for seasonal fertilizer bans is to prevent algal blooms, it just makes sense to enforce the bans in the summer, when blooms are most likely to occur.

Follow the money

Still, it’s true the call for winter fertilizer bans is based on when it rains and when it doesn’t: In the summer, consumers rain money on the fertilizer industry; in the winter, not so much.

So, when do you think the fertilizer industry would prefer to ban fertilizer usage?

VoteWater has already reported that the fertilizer industry and lawn care companies heavily fertilize state politicians. According to state campaign finance records for the 2022 election cycle:

  • Tampa-based Mosaic Company, the largest phosphate producer in the world, gave about $750,000 to state office-seekers and political action committees.
  • The Florida Phosphate Political Committee gave another $443,000.
  • The lawn care company TruGreen gives thousands to politicians and PACs and employs as lobbyists former House Speaker Steve Crisafulli and Karen Alexander Griffin, whose father, J.D. Alexander, was a Florida state representative and senator for 14 years.
The 2024 Florida Legislative session begins in January.

If UF researchers are looking for a fertilizer ban study that gives legislators and their benefactors just what they want, they won’t have to look far.

A recent study right there at UF/IFAS found that fertilizer bans help improve water quality in nearby lakes, but it suggests that winter bans may be more impactful than summer bans.

The seemingly extensive study analyzed “changes in water quality of lakes throughout the State of Florida from 1987 to 2018, comparing trends in water quality parameters before and after implementation of county-wide fertilizer ordinances.” Watch a presentation on the study at

Sam Smidt, lead author of the study and an assistant professor in the UF/IFAS soil, water and ecosystem sciences department, said in a UF news release that the study analyzed data from 160 natural lakes and stormwater ponds throughout Florida because they are “connected to all the waters in the area — rivers, streams, groundwater — so sampling lakes can inform us about the whole hydrological system.”

Smidt said the study “looks at fertilizer ordinances statewide and over a long period of time (emphasis added), revealing more generalizable patterns that can help inform how local communities decide to time ordinances to meet their water quality goals.”

Apparently, “a long period of time” is a subjective term.

Mapping problems with the study

The study produced a Florida map showing which counties have winter bans, summer bans, nonseasonal bans or no bans and the locations of lakes where data was gathered.

According to the map, three counties — Citrus, Hernando and Alachua — have winter bans. But no lakes in Citrus and Hernando counties were tested; a dozen or so lakes in Alachua County were tested.

​But data from Alachua County doesn’t really represent the effects of a dry season ban. The county’s regulations prohibit using landscape fertilizers with nitrogen from July through February, according to the county’s website. 

The rainiest part of the year in Alachua County is June 1 through Sept. 20, and the wettest month is July. So the so-called “dry-season ban” contains two and a half months of the rainy season, including the rainiest month.

Plus, the Alachua County Commission enacted the most recent version of the ban in April 2019 after the study’s data collection ended in 2018.

So much for the “30 years of water quality data” touted by the UF/IFAS news release.

Even Smidt, the author of the UF/IFAS study, admitted to the Miami Herald that the study lacks data from counties that switched from summer to winter bans.

“We can’t say conclusively from these data that you would see an improvement (from the switch),” he said.

Inconclusive results

There also are gaps in the data reportedly from counties with strict summer bans.

Collier County, for example, is shown as having a strict summer ban when, in fact, there is no countywide ban – only citywide bans in Naples (adopted in 2019) and Marco Island (adopted in 2016).

And Hillsborough County is shown to have a summer ban that “varies by jurisdiction.” And while it’s true Tampa has had a citywide summer fertilizer ban since 2011, lakes were tested throughout the county, which enacted a countywide ban effective in November 2021 – after the study’s data collection period.

A large number of lakes were tested in Polk and Osceola counties, which have only minimal, nonseasonal fertilizer restrictions suggested by the state, and Highlands County, which has no fertilizer ban at all. So that data doesn’t contribute anything to the summer ban vs. winter ban issue.

Also telling is where lakes weren’t tested.

According to the study’s map, Lake Okeechobee, the largest lake in Florida, wasn’t sampled – maybe because its fertilizer-based pollution comes from agriculture, not residential, sources. And no lakes were sampled in Martin County, which suffers some summers from massive algal blooms brought on by discharges from Lake Okeechobee, or Lee County, where red tide is a coastal scourge fed by Lake O discharges.

In fact, only four lakes in South Florida — in Broward and Miami-Dade counties — were sampled for the study.

So much for a statewide study.

The stakes are high

But flawed as this study may be, it’s likely to be a cornerstone of any argument by IFAS — and legislators — that summertime bans are ineffective and unnecessary. 

Worst-case scenario, legislators could try to roll back bans already in place.

This represents a reckless gamble with the health of our waters. As we’ve previously noted, summer fertilizer restrictions are literally the simplest thing local governments can do to try and curtail nutrient pollution in our waters; it is the lowest-hanging fruit. Significantly more needs to be done.

But here, we may be on the cusp of doing even less.

This is an issue VoteWater and our allies will be watching very closely during the upcoming legislative session. We’ll let you know if and when bad legislation is filed, by whom, we’ll follow it blow-for-blow, call out the legislators voting for it so that you might express your displeasure and identify those voting against it so you might voice your support.

Your involvement in this issue — making your voice heard — is going to be crucial if we’re going to head this off at the pass.