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 thatnitrogen (N) and phosphate (T_2O_5) surpluses were largest on dairyfarms (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.