Farm-gate nitrogen and phosphate balances

摘要

A standard methodology, based on input-output estimates for calculating farm-gate nutrient budgets, has been developed for use by farmers/advisers as a nutrient management planning tool. Results from using the tool on 171 commercial farms showed that nitrogen (N) and phosphate (P205) surpluses were largest on dairy farms (means of 248 kg ha~(-1) N and 46 kg ha~(-1) P_2O_5) and mixed arable farms with pigs or poultry (means of 278 kg ha~(-1) N and 65 kg ha~(-1) P_2O_5). Surpluses were lower on arable farms and arable farms with beef/sheep. For both nutrients, the largest inputs were from livestock feeds and inorganic fertilisers. Livestock products and crop produce were the major nutrient outputs. Balances were also calculated on a livestock product basis (e.g. kg per 1000 L of milk) and on a livestock unit basis (i.e. kg per 500 kg of animal live-weight), although for most users, it was recognised that balances calculated on a farmed area basis would be most easily understood.