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Technical Thematic Report No. 15. -Trends in residual soil nitrogen for agricultural land in Canada, 1981 2006

Changes in the Residual Soil Nitrogen (RSN) risk classes from 1981 to 2006

The RSN levels in 2006 were compared to the levels in 1981 (Figure 2). The land areas where RSN risk class decreased (that is, had lower RSN levels) were found in central British Columbia, southern Ontario, and southern Quebec. Most of the land in the Prairies Ecozone+ located in Saskatchewan and Alberta remained in the same risk class, however the eastern regions of the Prairies (Manitoba) increased RSN values by at least one risk class. Increases in risk class were also observed for the southeastern portion of the Boreal Shield, as well as the Atlantic Maritime The central portion of the Mixedwood Plains was found to have RSN values that remained in the same class over the 25-year period.

Figure 2. Agricultural land in Canada for which RSN changed by at least one risk class from 1981 to 2006.

map

Long Description for Figure 2

This map of Canada shows change in residual soil nitrogen (RSN) levels on agricultural land from 1981 to 2006. The land areas where RSN risk class decreased (that is, had lower RSN levels) were found in central British Columbia, southern Ontario, and southern Quebec. Most of the land in the Prairies Ecozone+ located in Saskatchewan and Alberta remained in the same risk class, however the eastern regions of the Prairies (Manitoba) increased RSN values by at least one risk class. Increases in risk class were also observed for the southeastern portion of the Boreal Shield, as well as the Atlantic Maritime The central portion of the Mixedwood Plains was found to have RSN values that remained in the same class over the 25-year period.

 

In summary, the RSN levels were in the very low and low risk classes for most of the Prairies Ecozone+ but high and very high RSN levels occurred in Manitoba, the central portion of the Mixedwood Plains Ecozone+, and the Atlantic Maritime Ecozone+ (Figure 1). RSN should be measured in these high risk areas, and if the in situ measurements correspond to model estimates, then management practices should be implemented which would reduce the risk of exporting RSN to waterways.

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