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UF Professor Develops Fertilizer For Healthier Palms, Soil And Water

This palm tree has yellow, dying leaves which is a symptom of potassium and magnesium deficiencies that was caused by fertilizing this palm with turf fertilizer. This is a very common problem in Florida landscapes and Broschat’s research has provided a way to prevent it.
This palm tree has yellow, dying leaves which is a symptom of potassium and magnesium deficiencies that was caused by fertilizing this palm with turf fertilizer. This is a very common problem in Florida landscapes and Broschat’s research has provided a way to prevent it.

After 25 years of work, a University of Florida professor published his study on developing an environmentally friendly fertilizer for the iconic Florida palm tree.

Tim Broschat, a UF environmental horticulture professor, developed a palm fertilizer suitable for Florida's soil and aimed to reduce water pollution during the summer.

Typical lawn fertilizers contain chemicals that can wreak havoc on natural aquatic ecosystems. During heavy rains in the summer, excessive nitrogen and phosphorus from fertilizers can run into bodies of water causing large algae blooms that kill fish.

There are county and state regulations that control the use of nitrogen and phosphorus in fertilizers during summer months because of resulting water pollution; Broschat worked to comply with these regulations.

He said plants like palm trees need a balance of certain types of chemicals to survive. Potassium, magnesium, manganese, nitrogen and phosphorus are included in the formula for a healthy plant.

But an imbalance in chemicals, nitrogen and phosphorus in particular, can cause issues for growth.

The standard lawn fertilizers many residential and commercial users apply have too much nitrogen and phosphorus in them. So much so that they can cause plants to suffer from nutrient deficiencies and can cause yellowing leaves or even death of the plant.

"You have to have nitrogen for palms the other times of year, but in the summertime, it's warm and there's usually plenty of rainfall, and that encourages the various microbes in the soil to degrade the organic matter," Broschat said.

Broschat developed a nitrogen- and phosphorus-free fertilizer to use during the summer and a nitrogen supplement to add for the rest of the year.

The new fertilizer uses a slow-release method. It releases its nutrients into the soil over a period of several months and is not as easily washed away by heavy rainfall.

In contrast, normal lawn fertilizers are water-soluble, meaning their main nutrients dissolve in heavy rains. These chemicals can flow into surface waters and groundwater, causing pollution, Broschat said.

After 25 years of research, Broschat worked for three more years doing fieldwork to make sure the new fertilizer worked. He published his findings last month in the scientific journal HortScience.

At this time, Broschat’s fertilizer is only available for commercial landscapers, but he said he hopes his developments will be implemented in residential areas.

"There aren’t a whole lot of options when it comes to homeowners," he said. "If people are aware of it and there's a need for it, the fertilizer companies will make it."

Garden centers are reluctant to carry Broschat's fertilizer because it's more expensive, but the environmental benefits and effectiveness toward plant growth should make it worth the extra buck, Broschat said.

He said he hopes his research will reach homeowners so they can see an improvement in their plants’ lives and help address the water pollution issue.

Erich Marzolf, the water resources division director of the Suwannee River Water Management District, said over-fertilization causes a big problem in the springs and lakes in his management area.

The Suwannee River and the Santa Fe River regions in particular have seen the results of the harmful pollutants, he said. Depending on the type of water body, be it estuary, lake, river or spring, the pollution can have different effects based on the chemicals already present.

"Most of the impairments in the Suwannee River and springs is associated with nitrate," Marzolf said. "Or, if you go over to the St. Johns River, phosphorus is really the key nutrient that is over-enriched."

"Generally, in springs, it's nitrogen that you focus on because that's what's being over-enriched and causing problems," he said. "It varies spatially."

According to county watershed management websites, 70 percent of Pinellas County waters have been polluted by harmful algae blooms that kill fish.

"The impairments have been identified as overgrowth of algae," Marzolf said. "You can get problems with dissolved oxygen becoming too low."

Fish and other water animals will die or move out of those areas because they cannot survive with such little oxygen, he said.

The Florida-Friendly Fertilizer Use on Urban Landscapes state ordinance restricts the use of certain chemicals in commercial and residential landscaping. Some counties including Pinellas, Hillsborough, Marion and St. Johns have also regulated nitrogen and phosphorus use for years.

However, the strictness of implementation for commercial and residential uses varies among counties.

"For us in Marion County, our fertilizer restriction is not as strict as some other counties," said Norma Samuel, a Marion County extension agent for the UF Institute of Food and Agricultural Sciences. "Some counties say you’re not supposed to be putting out any fertilizers at all in the summer."

Samuel said she recommends people use a low-phosphorus fertilizer when gardening.

If Broschat's new fertilizer becomes more available, homeowners could easily follow the county ordinances while providing their plants a healthy alternative for growth.

"We hope that when people find out that this is a better solution to fertilizing palms and landscape plants that it will create a demand so that more of the fertilizer companies will make this available to homeowners as well," Broschat said.

Marena is a reporter who can be contacted by calling 352-392-6397 or emailing news@wuft.org.