Farm-Level Phosphorus Budgets in High-Density Dairy Watersheds.

Managing nutrients from manure is becoming a high priority among most livestock farmers for economic and environmental reasons. The goal of this project is to: (1) Determine P balances on farms in two regions of high dairy density and nutrient impaired waters by examining imports of feed and fertilizer P, and off-farm exports of milk, animals, crops, and manure. And, (2) Select management strategies for bringing representative farms with a P-surplus, into P balance or below. Where soil-P values are excessive, propose strategies for feed, crop, manure, and fertilizer management that will reduce P transport to surface water. Data was collected from ten representative dairy farms, in Minnesota; each in Stearns and Goodhue counties in watersheds with P/eutrophication impairments. Data collected includes P composition and amounts of feed, forage, feed supplements imported and grown on the farm, fertilizer imported, and exports of P in milk, animals, crops, and manure for a one-year cycle. From the imported and farm-grown feed data we have determined levels of P typically fed and compared them to current National Research Council recommendations. We have computed P output from current feed rations models and also did a whole-farm P balance using current nutrient management models. We have examined the components of P imports and exports, as well as manure and crop nutrient management, to determine what feasible changes in feed, crop, fertilizer, and manure management would be most effective in reducing P delivery to surface waters on each farm.