WEST PALM BEACH — Why do best management practices (BMPs) work better to reduce phosphorus in runoff in some areas of the Everglades Agricultural Area (EAA) than others? A new study to be conducted by the University of Florida will conduct extensive testing on six farms in the EAA to answer that question.
The South Florida Water Management District (SFWMD) public workshop on Best Management Practices (BMPs) Research, Testing and Implementation to Address Water Quality Standards was held online on July 31.
SFWMD Ecosystem Restoration and Capital Projects Division Director Jennifer Reynolds said BMPs are mandated in the Everglades Agricultural Area (EAA) under the Everglades Forever Act (EFA).
The regulatory program and the stormwater treatment areas (STAs) together have helped reduce approximately 7,000 metric tons of phosphorus from leaving the EAA, said Reynolds. “The BMP program alone has prevented 4,000 metric tons of phosphorus from leaving the EAA,” she explained.
“State law required 25% annual reduction, and the EAA routinely meets or exceeds this requirement,” she said.
The EFA mandates a comprehensive program of research, testing and implementation of BMPs to address all water quality standards within the EAA and the Everglades Projection Area, explained Carmela Bedregal, of SFWMD.
She said the BMPs must be reviewed every five years.
Bedregal said the scope of work of the BMP research must provide reasonable assurance that six criteria are met:
• Provides verification of BMP effectiveness at 10 farms or at other locations in sufficient number to reflect soil and crop types and other factors that influence BMP design and effectiveness;
The EAA BMP master permit has been updated every five years since 1997, she explained. Research has included studies on phosphorus, pesticides and floating aquatic vegetation.
Dr. Samira Daroub of the University of Florida said the UF/IFAS research on BMPs in the EAA started in 1992 and the BMP program in the EAA was implemented in 1995. She said it includes water detention, fertilizer application controls, sediment controls and other factors such as pasture management and Xeriscaping.
She said all of the research is published.
There are farms that are very similar in size, crops planted, BMPs and general farm management but still have differences in phosphorus load in the discharged water, Daroub said.
“We are focusing on the soil,” she continued.
All EAA soils have an organic layer above bedrock, but the soils can be quite different, she said. They vary from 75% to 85% organic matter. East of the lake, the soils are deeper. The shallower soil south of the lake are lower in organic matter and contain more inorganic components.
Although EAA farms implement BMPs in a similar manner, there are differences in farm discharge of phosphorus concentrations or loads, she said. These differences may be related to soil properties, historical land use or cropping patterns. Research on mineral content of soils, phosphorus saturation and other properties may shed light on the reasons for the differences in BMP performance, she said.
Daroub said they have selected six farms, which will be studied in pairs. Each farm in a pair will be in the same basin, have the same farm operator and use the same BMP plan; however, one of the farms will have statistically higher phosphorus concentrations in runoff discharges. One pair of farms is in the S-5A basin, one pair in the S-6 basin and one pair in the S-7 basin.
“We will monitor these farms extensively,” she said. “We will water sample daily during discharges.”
The researchers will sample the soil, measure soil depth, monitor pH, measure organic matter content, monitor total phosphorus content and measure available phosphorus content.
She said this year they will start online BMP training, in part due to COVID-19 but also to make it easier for farmers to participate in BMP training.
In the public comment period, Gary Ritter of Florida Farm Bureau said he thinks the soil research is important and he is happy to see this important project south of the lake. He suggested soil research should also be conducted north of the lake. He said the canals that have cut into the spodic horizon may have changed the way nutrients move. He said they could also study the mobility of nutrients in the sandy soil.