OVERSEER® nutrient budgets - moving towards on-farm resource accounting

Nutrient budgets are useful tools for assessing the sustainability of nutrient flows within a farm and for highlighting potential negat ive environmental impacts of nutrient use. The OVERSEER® nutr ient budgets program is a decision support model to help users develop nutrient budgets. This paper outlines an upgrade to the OVERSEER® nutrient budgets program, with improvements in nitrogen (N), phosphorus (P), potassium (K) and sulphur (S), and addition of calcium (Ca), magnesium (Mg), sodium (Na) and hydrogen (potential acidity). Energy use and greenhouse gas emission profiles from farms have been included in the model. Using 'typical farm' and simulation studies, the paper then outlines how nutrient budget can be used to improve farm nutrient management. Keywords: acidity, calcium, energy, green house gas, inventory, lime, magnesium, maintenance fertiliser, nitrogen, nutr ient budgeting, phosphorus, potassium, resource accounting, sodium, sulphur