Sediment yield and seasonal soil erodibility for semiarid cropland in western Canada

Abstract

Despite its importance to the degradation of the land resource, few estimates of soil loss or soil erodibility for water erosion from cropland have been made for the semiarid Brown soil zone of western Canada. To estimate these, we calibrated the event-based Modified Universal Soil Loss Equation with measured sediment yield for three 5-ha fields near Swift Current, Saskatchewan. The calibration used predetermined C, LS, P, and warm-season K factors with all erositivities and the K factors for other seasons optimized. Using this calibrated equation with 31 yr of measured runoff data, mean annual sediment yield for a conventional-tillage spring wheat-fallow cropping system on an undulating landscape (0 to 5% slopes) was estimated to be 0.8 Mg ha−1 yr−1. Estimated erosion from fallow land from 16 March to 15 April constituted 86% of the mean annual sediment yield. Erosion occurring during rainfall-runoff were relatively unimportant, accounting for about 4% of the estimated total sediment yield. An exceptionally severe rainstorm was predicted to have caused erosion of many Mg ha−1but the frequency of such events on a given field is too low to greatly affect mean annual erosion. Apparent field-scale soil erodibility was least in the winter (November to 15 March) when the soil would typically be frozen to the surface and was greatest in April when the soil would typically be partially frozen. Apparent erodibility in the summer and in late March was intermediate between those values. Key words: Erosion, runoff, snow, Universal Soil Loss Equation