Validating the Residual Soil Nitrogen Indicator.

Residual soil nitrogen (RSN) is the amount of inorganic nitrogen that remains in the soil at the end of the growing season after crops have been harvested. The RSN indicator was estimated at regional, provincial and national scales over a 25 year period to determine where and when excess inorganic nitrogen remains in the soil and would be subject to loss through leaching and/or denitrification. Since these estimates are based on a budget model, it is critical to validate the model using field data.  Soil samples were collected from a range of agricultural fields in Ontario and predicted RSN values were compared to those that were measured after crop harvest. In general, there was good agreement between the predicted and measured values for a range of crops including corn, winter wheat, soybean and hay.