| The OVERSEER® nutrient budgets model assess the environmental impact of nutrient use within a farm using a series of reports for N, P, greenhouse gas emissions or energy, or a summary report which picks key outputs.
Each report has direct links to explanations of the indices and how they that can be used to assess the environmental impact, and to mitigation options for the user to consider.
In the N and P report, the indices shown are:
• N loss to groundwater
• N or P loss to water
• P runoff and risk factors (background, fertiliser, effluent)
• Potential nitrate concentrations in drainage water
• Farm N or P surplus– a measure of potential environmental impacts
• N efficiencies – a measure of how other management factors on the farm is affecting nutrient use and hence the environmental impact.
Additional indices can be set as regional councils or national bodies set these.
The greenhouse report shows greenhouse gas emissions as CO2 equivalents or as petrol equivalents associated with:
• methane emissions from animals
• nitrous oxide emissions from excreta, effluent, N fertiliser, or indirect sources.
• direct CO2 emissions associated with lime dissolution, N fertilizer manufacturing, fuel/electricity use and others
• capital – CO2 equivalents associated with setting up the property, discounted over the lifetime of each capital item
• processing CO2 equivalents associated with processing product from your farm.
The greenhouse calculations are based on the methods use for the national inventory calculations, adopted so that give results on a farm basis.
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