From the top of the main silo at Don Bennink’s North Florida Holsteins dairy farm, all I can see are cows – about 9,000 of them, grazing on some 2,500 acres. To the untrained eye, the scene is innocent and bucolic. But there’s something else going on here that, if not managed properly, can threaten ground water, the aquifer and springs. Cows are prolific producers of manure and urine. In an average day of grazing, milking and just mooing about, one dairy cow can generate more than 100 pounds of manure and urine. Multiply this by several thousand cows and you’ve got a serious potential source of groundwater pollution on your hands. Animal wastes washed directly into surface streams, sinkholes and leached through the soil by rainwater introduce nitrates into the groundwater.
The idea of disposing of tons of cow manure every day, no matter how it’s done, doesn’t paint a pretty picture. But the process itself is fairly straightforward, points out Bennink. In areas and facilities where cows are milked, fed and staged between the various phases of the milking process, wastes are removed through pressure-washing and scraping. Once flushed from these facilities, the manure, now a semi-solid sludge, is directed into holding ponds to await their final disposal through one of two techniques.
In the first of these techniques, the mixture is spread in a thin layer over a large field by truck so that the nutrients can be absorbed as fertilizer by a variety of nitrogen-absorbing plants like alfalfa and other grasses. In the second, cow manure mixture is further diluted with water and sprayed over a large area by a center-pivot irrigation system. In reality, neither of the techniques is foolproof; a percentage of the nutrients bypasses the root system and enters the underground aquifer. What makes Bennink’s dairy farm different is how he’s attempting to minimize this percentage.
In the first place, Bennink doesn’t think of cow manure as waste. Instead, he manages his farm as a closed system, using cow manure to fertilize the sorghum and other grasses the cows will eventually eat. In this way, he avoids the use of chemical fertilizers that can infiltrate the soil and gets rid of a significant percentage of the total volume of feces his cows produce in the process. Recycling cow manure as fertilizer, however, is nothing new. Bennink has simply taken the science of nutrient recycling one step further.
For the past 10 years, Bennink has worked proactively with state universities, government agencies and scientists from around the world to determine which varieties of grass provide the most efficient uptake of nutrients from the soil. In terms of reducing the overall amount of nitrates entering the aquifer from his farm, the discoveries have been more than surprising. Grasses like the Tifton-85 he uses on most of his fields today can absorb nitrates from the soil through their roots much faster than those which, only a few years ago, were recommended to dairy farmers around the state.
Bennink, who was an active member of the past Florida Springs Task Force, is interested in protecting springs and is sharing his experiences and encouraging other dairy farmers to follow suit.
“We’re proud of the progress we’ve made,” Bennink tells me, “People like to point fingers at dairy farmers and say we’re one of the worst polluters of the springs. But we depend on groundwater for our livelihoods, not just for recreation. Why would we want to pollute the resource we depend on most?” PD
—Originally published in: Florida Springs: Protecting Nature’s Gems - http://www.FloridaSprings.org
