Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 8, 2002
Publication Date: November 20, 2002
Citation: ROTZ, C.A., SHARPLEY, A.N., SATTER, L.D., GBUREK, W.J., SANDERSON, M.A. PRODUCTION AND FEEDING STRATEGIES FOR PHOSPHORUS MANAGEMENT ON DAIRY FARMS. JOURNAL OF DAIRY SCIENCE. 2002. v. 85(11). p. 3142-3153. Interpretive Summary: Phosphorus pollution of water from agricultural land is becoming an important concern on many watersheds. Prime examples are the Catskill and Delaware watersheds in southeastern New York. These watersheds, which are primarily covered with forests and dairy farms, supply 90% of the 1.3 billion gallons of water required each day for New York City. Because crop and grassland can provide a natural filter to supply clean water, agriculture is a preferred land use for these watersheds. Many factors affect phosphorus loss from dairy farms. These include the amount of feed and fertilizer brought onto a farm, the animal density on the land, feeding strategies, manure application procedures, crops grown, and topographic features of the landscape. A comprehensive study was done to determine management changes that dairy producers in southeastern New York can make to reduce the potential loss of phosphorus to the watershed while maintaining or improving farm profitability. Several production options were found to reduce or eliminate the long-term accumulation of soil phosphorus on farms while increasing profit. The best options were those that reduced the phosphorus fed to dairy cows and maximized the use of forage grown on the farm. These results will direct and encourage producers and those consulted by producers toward management options that improve their farm's potential impact on the environment while increasing profitability.
Technical Abstract: The long-term accumulation of soil phosphorus (P) is becoming an important concern on some watersheds heavily populated with dairy farms. Management changes in crop production and feeding may be useful in reducing this accumulation of excess P, but farm profitability must be maintained or improved to assure their adoption. Whole-farm simulation was used to evaluate the long-term effects of changes in feeding, cropping, and other production strategies on phosphorus loading and the economics of 100-cow and 800-cow farms in southeastern New York. Simulated farms maintained a long-term P balance if: 1) animals were fed to meet recommended dietary P levels, 2) the cropping strategy and land base used supplied all of the forage needed, 3) all animals were fed a high forage diet, and 4) replacement heifers were produced on the farm to utilize more forage. The most easily implemented change was to reduce the supplemental mineral P fed so that dietary levels now recommended by the National Research Council (NRC) were not exceeded, and this provided an annual increase in farm profit of up to $23/cow. Intensifying the use of grassland and improving grazing practices also increased profit along with a small reduction in P loading. A conversion from a dairy facility to heifer raising and an expansion from 100 cows to a 250-cow "state-of-the-art" confinement facility (with a 90% increase in cropland) were both found to be profitable options. These options also provided a long-term P balance for the farm as long as the production and use of forage were maximized and dietary P levels were maintained at the NRC.