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UF scientist with industry ties helps develop Hernando fertilizer rules

Laurie Trenholm is a professor of environmental horticulture at the University of Florida whose job includes, she said, "educating people how to manage lawns in an environmentally responsible fashion."

She is not an expert on groundwater, she told me, and "not a political person."

Yet there she was last week, appearing before the Hernando County Commission, where she was thanked for her help in developing a new fertilizer ordinance and where, in turn, she thanked the commission for not putting extra restrictions on fertilizing lawns in the summer.

This ordinance, which is virtually worthless for reasons I'll explain in another column, was required by the state because Hernando is home to a first-magnitude spring — Weeki Wachee — one that has also been classified as "impaired" because of nitrogen pollution.

So, yes, it's all about groundwater. And it is absolutely political.

Not just because this was a meeting of an elected body, but because fertilizer soaking and spilling into places it doesn't belong is probably the biggest water pollution problem in the state.

On one side are environmentalists who think there's an urgent need to do something, for example, about the nitrogen that has transformed springs from pools of sapphire to pits of slime.

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On the other side is, among others, the turfgrass industry, which says that what we're doing is fine. We just need to be a little more careful.

It almost goes without saying that this is Trenholm's side. Turf researchers have a long history of coziness with the industry, including accepting research money. A UF professor started the Florida Turfgrass Association, and Trenholm is a member of this and other industry and lobbying groups.

But that's not why she takes the position she takes, she said. It's because of a multiyear, $4 million study — funded solely by the state Department of Environmental Protection, she points out — that showed what happens when optimal amounts of fertilizer are applied to healthy, growing plots of the standard Florida lawn grass, St. Augustine.

Namely, the grass sucks up so much nitrogen that only about 1 percent of the amount applied seeps through the turf.

This is valuable information, of course. If we're gong to keep using chemical fertilizer, we need to know how to use it right.

But this study is also far too limited to support Trenholm's argument that we don't need summer fertilizer bans.

For one thing, in the real world, many people do not apply optimal amounts of fertilizer, and St. Augustine grass may very well not be healthy enough to absorb large amounts of fertilizer. In fact, it's the most notoriously sickly lawn cover there is.

Also, 1 percent of the tons of nitrogen applied in Florida every year is still a lot of nitrogen.

Diluted by a foot of water leaching through turf treated with those optimum applications of fertilizer, it amounts to a contamination rate slightly higher than the new state standard for springs.

There's also one other limit to talk about, which is clear once you look at Weeki Wachee and understand how excessive fertilization helped bring it to this sad condition.

The idea that all we need to do is be a little more careful? That's way too limited.

UF scientist with industry ties helps develop Hernando fertilizer rules 11/18/13 [Last modified: Monday, November 18, 2013 6:43pm]

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