Whole-farm XXXX balance on western dairy farms.

@entity8664 @entity1568 @entity291
Environmental legislation has made it necessary for livestock producers to be able to quantify and adjust the N balance on their farms. @entity8664 balance and efficiencies were computed for 41 commercial dairies in Utah and Idaho using the University of Maryland Nutrient Balancer. The average N balance, or unaccounted for N, was 81 tonnes per year for the average herd size of 466 @entity291 with 35.8% of the inputs accounted for in the outputs. The major inputs for farms that grew crops (n = 23, herd size = 284 total @entity291 ) were imported feed (57.4% of all inputs) and @entity1568 fixation (30% of inputs). The major outputs were animal products (primarily milk and some meat, 80% of outputs). For farms that grew no crops (n = 18, herd size = 700 total @entity291 ), 98% of the inputs were from imported feed. Of the outputs, 57% of the N was in animal products and 42.9% in manure and compost. Whole-farm balance per product for those farms that grew crops was most affected by herd N utilization efficiency (kg feed N per kg product N), crop N utilization efficiency, and availability of manure N applied to crops, while manure N storage efficiency was of lesser importance. For farms that grew no crops, whole-farm N balance per product was most affected by herd N utilization efficiency and manure N storage efficiency. Maximizing conversion of feed N to product N was the best way to reduce whole-farm N balance.
