Actual leaching from a farm block will vary year-on-year due to variations in weather — sometimes quite significantly. Because OverseerFM was designed to help farmers test the impact of different farm management practices, it removes short term variability (such as weather events) so farmers can make good decisions for the long term. The model therefore estimates the nutrient leaching or gas emissions that are likely to occur in a typical year if the management system described remains in place. It is not a one-off prediction for a single year.
The OverseerFM results are therefore best used to create a baseline for each farm, and to guide and measure improvement over time.