Skip to main content

UF Study Shows How Large Dairies Can Practice Organic Farming

Karen Meisenheimer

Tito French (352)392-1811

GAINESVILLE–While many activists consider dairy waste to be the latest environmental criminal, a University of Florida agronomy expert says it could be a valuable resource if managed correctly.

“Dairies produce a large amount of organic reSources,” said Tito French, of UF’s Institute of Food and Agricultural Sciences. “Everyone loves organic farming, and here we have an opportunity to put organic farming concepts into practice in large agriculture.”

French heads up a team of scientists studying the application of dairy waste to crops, field testing various crops for their ability to use dairy manure as fertilizer.

Preliminary results from the four-year study have indicated that growing a permanent crop of bermudagrass on the spray fields best absorbs nitrates while allowing only minimal amounts into the surrounding environment.

The Florida Department of Environmental Protection is funding the research project at North Florida Holsteins near Bell in Gilchrist County.

“We’re looking how to manage that valuable resource in a manner that will provide two things,” French said. “One – an agriculture product or forage that goes back to the feeding animals, and two – maximum utilization of the applied nutrient to the extent that little is lost to groundwater.

“By recycling this valuable nutrient resource we can design a system that is more sustainable,” he said.

One milking cow can produce as much as 125 pounds of manure a day and 15 gallons of urine. Modern dairies typically use a flushing system that washes the excreted material to a central system, often a lagoon lined with concrete. The effluent then is pumped out and sprayed onto the crops as fertilizer.

Dairy critics are concerned that nitrates found in the waste and fertilizers are seeping into springs and drinking water. The debate has been especially strong in the Middle Suwannee River Basin where the number of dairies has increased significantly over the last 10 years.

Dairy farmers in north Florida have traditionally planted corn in the spring, sorghum in the summer and rye in the winter as livestock feed crops.

North Florida Holsteins milks close to 3,000 cows three times a day and provides an ideal test site, French said. Scientists discovered that planting bermudagrass, followed By winter rye absorbs more nutrients from the cow manure compared to the traditional system.

“With the traditional cropping system, you have periods at the front end and the tail end of each crop where nothing is utilizing the nutrients,” French explained. “The key is to maintain a growing crop that will continuously take up nutrients from the applied effluent.”

Five different cropping systems are being tested with varying rates of effluent application. Researchers analyze both the soil and soil solution taken from different depths in the fields to check for nitrate levels.

Analyses from the rotation of bermudagrass and rye show that none of the samples contained nitrate concentrations below the root system that exceeded the federally-mandated safe level of 10 parts per million. Most of the nitrate quantities identified were below five parts per million.

Ken Woodard, research scientist with the UF agronomy department, said bermudagrass is the “star of the show” so far because it is an aggressive crop that provides a constant concentration of roots, facilitating maximum soil nutrient absorbtion.

“Another promising system is corn planted into the bermudagrass in March when the grass is pretty inactive, but still has the ability to uptake nutrients,” Woodard explained. “The grass and corn compete with each other until the corn overtakes the grass.”

French said the study of effluent on cropping systems in Florida started in the early ’90s at UF’s dairy research unit in Hague. Dairy producers funded the original study through the Dairy Check-Off Program, which generates money By charging each producer based on pounds of milk sold.

“They (dairy farmers) have a sincere interest in finding all the solutions,” French said. “They also live and raise their families in Florida. It’s to their own benefit to do a better job and they realize that.”

Don Bennick, owner of North Florida Holsteins, said he is pleased to host the UF research project. His dairy and its soil provide a good representation of the area where a great deal of concern over nitrate levels in groundwater has developed.

“We want to do everything we can to protect the water supply and the environment,” he said. “We don’t know all the right answers, so we support finding them based on science and not on conjecture. The whole purpose of working with these folks is to come up with the right answers.”