Abstract

Many governmental programs that address non-point source pollution from animal feeding operations havefocussed on promoting land-based best management practices (BMPs). Our objectives were to illustrate and quantify nitrogen (N) and phosphorus (P) balances of Northeast and Mid-Atlantic dairy farms using (1) a hypothetical and representative Northeastern and Mid-Atlantic dairy farm, and (2) three case study dairy farms with animal densities of 1.6 to 2.4 milking cows ha^-1. Analyses of N and P balances for the representative farm showed an annual surplus of 258 kg N and 31 kg P₂O₅ ha^-1. For the three case study farms, 65-73% of the N and 41-62% of the P that entered the farm through feed, fertilizer, fixation, animal purchases and/or bedding were not exported in the form of milk, animals or crops, resulting in excesses of 114-248 kg N ha^-1 and 37-42 kg P₂O₅ ha^-1. These quantifications suggest that land-based BMPs to address non-point source pollution will fall short of expectations over the long-term because they do not recognize the strategic issues faced by many of today’s dairy farmers in the Northeast and Mid-Atlantic regions. We conclude that for the long-term sustainability of the dairy industry, a land-based BMP approach should be complimented with whole farm nutrient mass balance assessments and address nutrient source reduction and/or manure treatment and export. The latter requires a change in cropping systems and/or innovative systems to treat the manure to decrease transport costs and/or add economic value.

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