NITROGEN FLOW ON 2 LIVESTOCK FARMS IN ONTARIO - A SIMPLE-MODEL TO EVALUATE STRATEGIES TO IMPROVE N-UTILIZATION

Improving N utilization on livestock farms reduces the requirement for external N inputs and also reduces the risk of soil, air and water pollution. Calculation of N flow on two livestock farms in Ontario showed that 17-21% of imported N was exported as farm products, A simple model was developed for livestock farms to measure the change in farm N utilization following improvements in N utilization by animals through changes in diet, increased N retention during manure collection and storage, and increased manure N utilization by crops following field application. On a dairy farm, improving N utilization by dairy cattle from 16% to 25% through changes in animal diet increased the whole-farm N utilization from 18.8% to 28.5%, whereas increasing manure N utilization by the crop from 27% to 50% increased the whole-farm N utilization from 19.8% to 22.1%. The highest priority for improving farm N utilization and decreasing the risk of environmental pollution on livestock farms is by improving N utilization by animals. through improved feeding strategies.