A field method for soil erosion measurements in agricultural and natural lands

Abstract

Soil erosion is one of the most important watershed processes in nature, yet quantifying it under field conditions remains a challenge. The lack of soil erosion field data is a major factor hindering our ability to predict soil erosion in a watershed. We present here the development of a simple and sensitive field method that quantifies soil erosion and the resulting particulate nutrient movements in a landscape. The method is based on the principle of the mesh-bag (MB) method that quantifies the redistribution of the eroded soil in a field. The mesh bags allow water and a negligible amount of soil particles to infiltrate the bottom mesh because they are intimately in contact with the bare soil surface. We evaluated the MB method with a runoff plot method and confirmed that soil erosion on a slope assessed by the two methods is significantly and positively correlated. The efficiency of the MB method to assess soil erosion increased with decreased slope or increased plot size. The practical upper limit of the MB method to assess total soil erosion is 15.5 t ha−1 (6.3 tn ac−1) in 26 to 47 m2 (280 to 506 ft2) plots with 5% to 10% slopes and 6.5 t ha−1 (2.6 tn ac−1) in a 35 m2 (377 ft2) plot with 25% slope. Mesh-bag sizes, ranging from 10 × 10 to 30 × 30 cm (3.9 × 3.9 to 11.8 × 11.8 in), had no significant effect on the amount of soil erosion assessed. The spatial and temporal patterns of soil erosion and the associated nutrient movement revealed by the MB method may provide valuable insights into the soil erosion processes in agricultural and natural lands.