Agricultural land use can impact the sustainability of inherent soil quality by its influence on the extent, severity, and dynamics of soil salinity. To assess this impact, a salinity risk index was developed and applied to the agricultural region of the Canadian prairies, utilizing land-use data sets for 1981 and 1991. The analysis is presented in map form. The total extent of moderate or more severe salinity for the prairie region, as determined from a summation of each provincial map, is 1.4 million hectares. The risk assessment based on 1991 land-use data indicates that 62.2 percent of the farm land has little to no risk of a change in salinity, 27.9 percent has a moderate risk, and 9.9 percent of the land has a high risk. A comparison of the risk index classes for the 1981 and 1991 land-use data indicates that risk of salinity for the majority of the land (92 percent) hat not changed, whereas less than 7 percent of the land had a lower risk class, and approximately 0.5 percent had a higher risk class in 1991.

Moderate to severe soil salinity currently affects the surface 60 cm of approximately 1 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. Key words: Risk of soil salinization, dryland salinity, land use, summer fallow, permanent cover

The thicknesses of self-mulching A horizons were studied in native grassland and cultivated glaciolacustrine clay soils in southwestern Saskatchewan to estimate the extent of erosion and evaluate the relationship between slope characteristics, erosion and sedimentation. It has been shown that under similar gradient, the thickness of the A horizon, in the erosional portion of slopes, is less under cultivated than native grassland conditions; whereas, in the depositional portion the thickness of the A horizon is greater under cultivation. Erosion equations were developed which indicated 7.4 kg∙m−2∙yr−1 or 0.57 cm/yr for a 7.5% backslope and 2.1 kg∙m−2∙yr−1 or 0.16 cm/yr for 2% backslope. Calculated losses of organic matter from the most severely eroded slopes amounted to 650 kg∙ha−1∙yr−1. Comparable losses of nitrogen were 65 kg∙ha−1∙yr−1. This represents a 41% and 35% loss in organic matter and nitrogen, respectively, under nearly 70 yr of cultivation. The very close relationship shown in this study between various slope attributes and erosion clearly indicates the importance of slope considerations in all erosion studies. Key words: Erosion, deposition, swelling clay soils, landscape analysis, organic matter loss