Estimating long-term erosion and sedimentation rate on farmland using magnetic susceptibility in northeast China

Abstract

Soil loss is a global environmental issue. Increasing amounts of attention have been paid to assessing soil erosion and its distribution on cultivated slopes using magnetic susceptibility (MS), which is a rapid, reliable, economic and nondestructive method. However, the MS technique provides incomplete estimates of soil loss. The objective of this study is to employ MS as a tracer to estimate soil loss on cultivated slopes in northeast China. A typical degraded sloping farmland area with a 40-year history of cultivation and a reference forest site were selected. The eroded and deposition regions were distinguished and the tillage homogenization model was used to predict variations in MS with erosion depth. The soil erosion depth, deposition thickness, soil loss, and soil erosion rate were calculated by matching the MS profile measured in the farmland sites to the reference forest site. The results showed that nearly 64% of the area of the selected slope had been eroded, and sediment produced by erosion had been deposited on 36% of the slope as a whole. The largest MS values occurred on the lower portion of the slope (a deposition area), whereas the smallest values occurred on the middle portion of the slope (an eroded area). The average eroded soil depth was 44.5 cm or 1.1 cm·yr-1, and the average deposition thickness was 35.5 cm or 0.9 cm·yr-1. The total amount of soil loss from the sampling slope was 29,338.4 t, which corresponded to a rate of soil loss of 4,630.5 t·km-2·yr-1 over the 40-year cultivation period. This result was similar to those obtained by previous studies conducted in the same region using other methods and techniques. Thus, soil MS was demonstrated to be a reliable tool that can be used to quantify soil erosion on cultivated slopes in northeast China.