UF Researcher: Phosphate Waste Product Makes A Good Fertilizer

Ed Hunter (352) 392-1773 x 278

Jack E. Rechcigl rechcigl@gnv.ifas.ufl.edu, (941) 735-1314, ext. 209

ONA — Low-cost fertilizer could be the answer to dealing with the more than 1 billion tons of waste material accumulated by Florida’s phosphate mining industry, new research at the University of Florida shows.

“We think the best use of the material is to spread it out on pasture land in a very thin layer,” said Jack E. Rechcigl, a soil and water science professor with UF’s Institute of Food and Agricultural Sciences. “This is a natural material that came from the ground.”

Rechcigl, a researcher at UF’s Range Cattle Research and Education Center in Ona, presented the findings of his 10 years of research Wednesday (8-25) at the American Chemical Society’s annual meeting in New Orleans.

Florida is the No. 1 producer of phosphate in the world. The by-product of the phosphate production process, phosphogypsum, is potentially an excellent source of sulfur and calcium for farmers and ranchers, he said.

“We actually were able to demonstrate that it was very beneficial for pasture grasses,” Rechcigl said. “We could increase the yield, or the quantity of the grass grown, by as much as 20 to 25 percent. We were also able to increase the quality of the grass.

“The higher the quality of the grass, the better weight gains we will get in our cattle. We want a high-quality forage for cattle production, and we also want as much forage as we can produce,” he said.

One potential drawback to using phosphogypsum as a fertilizer is that it contains low levels of radium-266, a slightly radioactive compound. Because of the radium content, the material is regulated by the Environmental Protection Agency.

“The material is regulated because radium decays to radon gas and radon gas has been linked to lung cancer in humans,” Rechcigl said.

But with funding from the Florida Institute of Phosphate Research, an independent state agency funded by a tax charged on phosphate production, Rechcigl’s study indicates there are no environmental concerns with the use of phosphogypsum fertilizer.

Under a special use permit from the EPA, the study tested phosphogypsum with radium contents approaching twice what is allowed for fertilizer use. When comparing a field that had phosphogypsum applied to a field that was not treated, the researchers detected no potential environmental problems.

“We showed that when we applied agronomic rates of phosphogypsum to the land — the amount needed to meet the sulfur requirement for the plants — we could not even detect any increases in radon gas,” Rechcigl said. “We did not believe there were any environmental hazards from applying agronomic rates of phosphogypsum.”

Rechcigl said the study also looked for, but did not find, evidence of increased radium or any radium by-products in the groundwater or surface water runoff from the test fields. Even though the results of the current study show that phosphogypsum has no negative environmental impacts when used as a fertilizer, Rechcigl said one final study is needed.

“Before we can get ranchers to use it in their cattle grazing, there really needs to be one last study where we would look at it under grazing conditions,” Rechcigl said. “We need to actually look at the intake of the material into the cattle, slaughter the cattle and measure it in the meat.”

Gordon Nifong, research director for the phosphate institute, said the UF study is the first step toward getting the EPA to allow increased use of phosphogypsum as a fertilizer.

“Jack Rechcigl’s work has shown in one major study that there is no significant increase in the hazard in its use,” Nifong said. “This has brought its use to the attention of the agricultural community worldwide. But it is going to take a lot more research and more findings before the EPA gets convinced.”

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