Predicting the Residual Soil Inorganic N and Nitrate Leaching Losses at a Regional and National Scale Using a Canadian Agricultural Nitrogen Budget Model (CANB v3.0).

The Canadian Agricultural Nitrogen Budget model (CANB v3.0) was developed to estimate two Agri-environmental Indicators; Residual Soil Nitrogen (RSN) and the Indicator of Risk of Water Contamination by Nitrogen (IROWC-N) at the 1:1 million spatial scale every 5 years (census years) from 1981 to 2006. RSN (kg N ha^-1) is an estimate of the amount of N remaining in the soil after crop harvest. IROWC-N is an estimate of the concentration of nitrate and amount of N lost between cropping seasons,  The average RSN in Canada increased from 9.3 kg N ha^-1 in 1981 to 25.6 kg N ha^-1 in 2002 and then decreased to 17.7 kg N ha^-1 in 2006. Nitrate losses varied from 2.1 in 1981 to 2.6 kg N ha^-1 in 2006, and nitrate concentrations in leached water increased from 2.2 mg N L^-1 in 1981 to 5.3 mg N L^-1 in 2006. The changes in IROWC-N can be explained mainly by the gradual increase in RSN values over time as well as the over-winter precipitation and drainage rates. There were significant differences in RSN and IROWC-N spatially and temporally.