WIND-TUNNEL TEST OF THE INFLUENCE OF MOISTURE ON THE ERODIBILITY OF LOESSIAL SANDY LOAM SOILS BY WIND

Loessial sandy loam soils are the major soil categories in the norther n Loess Plateau, China, Owing to a dry, windy climate and sparse surfa ce cover, wind erosion is a serious problem and dust (sand) storms occ ur frequently. Soil moisture is one of the most important factors infl uencing resistance to wind erosion. The influence of moisture content on the erodibility of sandy loam soils was investigated through wind t unnel simulations. Results showed that the threshold velocity for soil particle movement by wind increases with increasing soil moisture by a power function. The intrinsic factor in the increase in soil resista nce due to moisture content is the cohesive force of soil water. Cohes ive forces of the film and capillary water are different; the influenc e of soil moisture on threshold velocity was shown to follow a steplik e pattern. The wind erosion modulus of sandy loam was directly proport ional to the cube of the wind velocity or the square of the effective wind velocity (V-V-t). There existed a negative exponential relationsh ip between the wind erosion rate and soil moisture content. Initially, as soil moisture increased the decrease in the wind erosion rate was rather rapid. When the moisture content reached more than 4%, the rate of decrease in erosion slowed and became almost constant with success ive increments of moisture. This suggests that different soil moisture contents can prevent wind erosion at different levels. Four percent s oil moisture could only reduce the erodibility of the sandy loam soil by a small degree. (C) 1996 Academic Press Limited