A Method to Estimate Soil Loss From Erosion

Abstract

Abstract We have developed a new x‐ray spectrograph procedure for quantifying the extent of soil loss from erosion. Methods which rely on topsoil thickness or depth to the top of either the clay maximum or argillic horizon underestimate soil loss from accelerated erosion. Each soil examined has a characteristic mass absorption coefficient (µ M ) line when plotted as a function of soil depth. As a soil erodes, the mass absorption coefficient line is altered. The maximum value of µ M reflects the accumulation of elements high in atomic mass including weathering products such as Fe and bases. The lower boundary of the subhorizon of maximum µ M coincides with the lower boundary of the argillic horizon for all pedons examined. The maximum value of µ M is one or two subhorizons below the zones of maximum clay and cation exchange capacity (CEC). The depth to maximum clay underestimates the amount of erosion when part of the clay maximum has been mixed into the topsoil by tillage. The change in depth to the lower boundary of the argillic horizon and/or subhorizon of maximum µ M are the best indicators of the amount of soil removed from an eroded pedon when compared with a slightly eroded (reference) pedon. These parameters are less likely than the clay maximum to be removed by accelerated erosion because of their greater depth in the profile. This procedure was tested using soils with argillic horizons and should be useful for soil erosion studies in areas having Alfisols, Ultisols, and Mollisols with argillic horizons.