Application of a risk indicator for assessing trends in dryland salinization risk on the Canadian Prairies

Moderate to severe soil salinity currently affects the surface 60 cm of approximately I million ha within agricultural regions of the prairies. The subsoil (60-120 cm) is affected on about 3.5 million ha. The risk of soil salinization (RSS) indicator was developed to measure and monitor the change in risk of soil salinization in the Canadian Prairies as a function of changes in agricultural land use and management practices as reported in the Canadian Census of Agriculture. We have expressed the RSS indicator in five classes from very low to very high risk. In 1981, 18.4% of the land area in the agricultural regions of the prairies was rated as having a moderate or higher risk of salinization. By 2001 this had improved to less than 12% (8 million ha). Prairie-wide the land area at high and very high risk of salinization decreased from 6.2 to 4.4% of agricultural landscapes and the area at moderate risk decreased from 12.2 to 7.3%. We attribute this improvement largely to a reduction in summer fallow with a minor contribution from increased use of permanent cover. Although the risk of soil salinization is far from eliminated, the trend is towards greater agri-environmental sustainability.