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Reprinted with permission from University of Wisconsin College of Agriculture and Life Sciences Whole-Farm Approach Handles Phosphorous on Dairy Farms What goes in must come out, and in the case of phosphorus, too much has been going into cows and coming out on farmlands. New state and federal rules aimed at curbing runoff pollution are going to affect many Wisconsin farms. The bad news: surveys show that phosphorus levels in most Wisconsin farm soils are too high, and if they conduct business as usual, many dairy farms will not be able to comply with the proposed phosphorus rules. The good news: proper whole-farm phosphorus management will allow most of those farms to meet the regulations, according to Mark Powell, an agroecologist at the USDA-ARS Dairy Forage Research Center. Powell has studied how phosphorus management in one dairy system component (e.g. feed) affects other system components (soils and crops), and how whole-farm phosphorus management can help producers comply with forthcoming nutrient management regulations. He discussed his findings Jan. 15 at the Wisconsin Fertilizer, Aglime & Pest Management Conference. In 1999, 75 percent of the major soils in Wisconsin tested above high (24 ppm) and 50 percent tested greater than excessively high (38 ppm) in phosphorus levels, according to UW-Madison studies. On dairy farms, these increases usually occurred because imports of phosphorus in feed and fertilizer exceeded exports in milk, cattle, and surplus grain or hay. Many of the environmental problems facing animal agriculture are due to the separation of livestock production from its feed supply, Powell says. Swine and poultry operations usually import their feed, and new phosphorus regulations will pose major hurdles for those industries. On the other hand, most Wisconsin dairy operations raise most of their own feed and recycle manure through cropland. Powell's research has shown that most state dairy farms have stocking rates of less than 0.44 cows per acre, the threshold value for self-sufficiency in forage and grain production. Self-sufficiency means that a farm has adequate land to recycle its manure phosphorus through crops. Self-sufficient stocking rates will vary from farm to farm. Farms feeding recommended levels of phosphorus and spreading manure on all their available cropland can maintain higher stocking rates without increasing phosphorus runoff than farms feeding phosphorus excessively and spreading manure on only parts of their cropland, Powell notes. "On many dairy farms, the phosphorus problem originates not so much from excessive stocking rates but rather from a combination of high dietary phosphorus levels and inadequate utilization of available cropland for manure spreading," Powell says. Balancing phosphorus inputs and outputs through proper feed, fertilizer and manure management is the first step toward reducing soil phosphorus buildup and runoff phosphorus losses from dairy farms.

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