Rising nitrate levels — most likely from farms and homes in the region — along north Florida's famous Suwannee River are prompting concerns about the nutrient's effect on the environment and public health.
“The federal safety standard for nitrate-nitrogen in drinking water is 10 parts per million, but in some areas we are finding levels in the 20 to 30 ppm range,” said David Hornsby, water quality analyst with the Suwannee River Waster Management District in Live Oak.
The district and the Florida Department of Environmental Protection have been monitoring water quality in the Middle Suwannee River Basin for the past 12 years. Hornsby said rising nitrate concentrations in the river, springs and groundwater have become “a regional phenomenon” in the past few years.
There have been no reports of health problems related to nitrates, but the potential is there, said Elaine Turner, assistant professor in the University of Florida's food science and human nutrition department.
“The problem could be most serious for infants,” she said. “If infants consume formula made with water that exceeds the nitrate health standard, a condition called methemoglobinemia or “blue baby syndrome” can result. Hemoglobin carries oxygen in the blood, but methemoglobin cannot carry oxygen, causing symptoms of oxygen starvation.”
In addition to making drinking water unsafe, high nitrate concentrations can lower water quality in rivers and springs, causing algae blooms that consume oxygen needed by fish and other aquatic animals.
The basin, which includes Lafayette and Suwannee counties, has hundreds of residential and commercial septic systems in rural areas, about 300 row crop and vegetable farms, 44 dairies with more than 25,000 animals and 150 poultry operations with more than 38 million birds, said Don Graetz, a professor with UF's Institute of Food and Agricultural Sciences. Suwannee County is the Number One poultry production area in the state.
“All of these activities have the potential to adversely affect water quality in the basin,” Graetz said. “At this time, the public perception points to animal waste and fertilizer as the most likely causes.
“Surface and ground waters interact in most of the basin due to the region's active hydrology and porous soils. The mobility of nitrates, regardless of the source, makes it critical that we carefully evaluate where and how they enter the aquifer,” he said.
A three-year $1.4 million grant from the state environmental protection agency and the U.S. Environmental Protection Agency is supporting UF work.
In addition, concerns about the nitrate problem have prompted 24 public and private agencies to form a partnership to control the nutrient. The Suwannee River Partnership, also known as the Suwannee River Basin Nutrient Management Working Group, includes representatives from the university, agriculture, state and federal agencies, local governments and related associations. The partnership has established technical committees to develop and promote strategies for monitoring and managing animal waste, fertilizer and human waste in the region.
“The agricultural community, which is the key to the area's economy and green space, is just as concerned about protecting water quality as anyone else, and we're all working together without finger-pointing or blame,” Graetz said.
Graetz and others in the partnership are cooperating with three producers in the basin to monitor groundwater quality and evaluate the effectiveness of best management practices, or BMPs — solutions that are fair and workable for everyone involved.
The agricultural side of the partnership includes Barnes Poultry Farm in Live Oak, Byrd Dairy Farm in Mayo and Suwannee Farms in O'Brien, which produces row crops and vegetables under more than 40 center pivot irrigation systems on 5,000 acres.
Kenneth Hall, manager of Suwannee Farms, said the project provides a “unique opportunity” to observe nitrate movement through the soil in relation to crop development and irrigation or rainfall.
“If we can do a better job of maximizing nutrient and water efficiency, while maintaining economic sustainability, we certainly want to be among the first to do so,” he said.
George Hochmuth, director of UF's North Florida Research and Education Center in Live Oak, is developing management practices for Suwannee Farms.
Wendy Graham, a professor and hydrologist in UF's agricultural and biological engineering department, is monitoring soil and groundwater quality and water movement at all three farms.
She said data will be used to evaluate BMPs and develop computer models for predicting the effects of various nutrient and water management practices on groundwater quality and crop yield under different soil, weather and cropping conditions.
“We have 13 to 20 monitoring wells at each one of these farms, and we are currently measuring nitrate concentrations in soil and groundwater under existing management practices,” Graham said. “At Suwannee Farms, our monitoring wells are under one of their large (140 acre) center pivot irrigation systems.
“This year, we have begun to implement BMPs on this center pivot to help protect groundwater, while maintaining profitable crop yields. As new fertilizer and irrigation management practices are tested over the next two years, we will continue to evaluate water quality and crop yield, making further adjustments as needed,” she said.
“If the research proves successful, groundwater concentrations directly below farms using the BMPs are expected to decline within two to four years,” Graham said. “However, because of the complexity and uncertainty of the flow paths within the Floridan aquifer, it could take up to 20 years to see measurable improvement in the springs that flow into the Suwannee River.”