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NMPs versus SUVs: cows, commuters and manure management on Madison’s urban fringe

Dane County, Wisconsin is home to more than 120,000 dairy cows and some of the most productive farmland in the state. It”s also home to some of the hottest house-building in the state, thanks to a thriving job market in and around Madison, the capital city. And it”s home to some thorny urban/rural problems, as dairy farmers try to manage manure in a countryside that”s filling up with houses and commuters.

In an effort to minimize water pollution, federal and state regulators are emphasizing nutrient management plans for dairy farms and other livestock operations. An NMP is a written plan developed to provide crops with enough nutrients — nitrogen, phosphorus, and potassium — to produce optimum yields, while keeping nutrient runoff out of waterways. NMPs can help dairy farmers maximize the value of manure applied to croplands, saving on fertilizer costs, reducing soil erosion, and protecting water quality. But plans that look great on paper don”t guarantee success in the real world, according to a University of Wisconsin-Madison researcher.

Based on his studies of farm and livestock operations near Madison, rural sociologist Pete Nowak says that farmers near urban areas are going to have an increasingly difficult time meeting the requirements of NMPs.

“Suburbanization is reducing farmers” ability to manage manure in an environmentally sound fashion,” Nowak says. He lists several ways that sprawl limits farmers” options:

* Fragmentation of the land base – rather than contiguous units, farmers wind up with a piece of land here and a piece there, making it more time-consuming and logistically difficult to haul manure to all these different spots.
* Increased commuter traffic – meaning longer and longer waits to cross intersections with loaded spreaders, along with complaints about manure on the roads and farm machinery slowing traffic. Safety concerns also arise when fast-moving commuter cars mix with slow-moving machinery.
* Increased competition and prices for land on which to grow crops and spread manure. To get land now, farmers must bid against housing developers; developers win the bidding. Land lease rates are rising and leases, when available, tend to be short-term only.

“It”s almost like we”ve put these higher expectations on the producer, and at the same time we”re tying one hand behind his back. This is one reason I don”t think NMPs will work in urbanizing areas,” Nowak says. “We have to understand the farmer”s situation, from the subfield up to the entire watershed, before we design and implement these manure management regulations.”

NMPs are based on fields, and agronomists don”t consider that a farmer with a loaded manure spreader may not be able to get to a certain field due to weather or traffic, according to Nowak. In addition, agronomists often overlook the “full load principle.” A farmer begins spreading with a fully loaded manure spreader, whose load doesn”t always neatly match a field”s manure requirements. The farmer is going to empty that spreader before returning to the barn for another load. “Agronomists can specify all they want, but farmers work with full loads,” Nowak says. “Some fields may get too much manure and some too little.”

In other words, scientific data that fits neatly on spreadsheets doesn”t always correlate with farmers” actions on fields. “In our survey, only half the operators knew how much manure their spreader carried. So how do you know how much you”re spreading if you don”t know how much you”re carrying? This is where rational science doesn”t account for social reality,” Nowak says. “What works in the lab and in experimental plots can break down when applied to working lands.”

Nowak and his colleagues are looking at how the human factor influences manure management, as well as how that management influences nutrient runoff.

Nowak and post-doc student Perry Cabot are monitoring two sub-watersheds north of Madison, one managed by small farms and one managed by larger farms. The nine farms on the two sub-watersheds feed into Lake Mendota and the Madison chain of lakes, where phosphorus management efforts are underway to reduce eutrophication.

“We”ve done high-density grid-sampling on all the soils for phosphorus content. We know the baseline conditions and are tracking phosphorus now. So far, we have 20 months” worth of data, and we hope to go for five years to see what happens as farms go through crop rotations. We have sampling equipment set up on the nine farms to monitor water quality at the sub-field, field, edge of field, edge of farm, and sub-watershed levels,” he says. “This allows us to monitor the relationship between manure distribution patterns, water quality parameters, and variations in weather.”

Nowak has been meeting with the nine farmers to discuss the issues and constraints they face. Realizing that manure management is not going to get easier in the future, the group is seriously considering a biodigester, in which anaerobic bacteria break down organic material, such as manure, and produce methane gas. The system captures the gas for generating electricity, and the liquid effluent from the digester can be used as fertilizer.

Rather than installing a small biodigester on each farm, the group is considering a community digester to which all farmers in an area would bring their manure. While it would generate energy, the digester would function primarily as an environmental/sustainable agriculture process, rather than as an alternative energy source, Nowak says.

The digester would process manure from 7,000 to 10,000 cows, and could also handle food wastes from area restaurants (tests have shown that food wastes can boost digester performance). Hired technicians would manage the digester (the participating farmers prefer to milk cows), Nowak adds.

Farmers have agreed to take the solids from the digester to use for bedding. Nutrients in the liquid stream will be transported outside the watershed, and possibly sold as liquid commercial fertilizer. Any profits from the digester would be used to buy development rights around the participating farms.

“The digester would enhance water quality, protect farms, and help to create a greenbelt,” Nowak says. “It”s a win for everybody, and this is rare in complex situations.”