ESTIMATION OF SOIL EROSION AND DEPOSITION BY A LANDSCAPE ANALYSIS TECHNIQUE ON CLAY SOILS IN SOUTHWESTERN SASKATCHEWAN

Abstract

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