Soil erosion by wind

Soil erosion by wind may occur wherever dry, sandy or dusty surfaces, inadequately protected by vegetation, are exposed to strong winds. Erosion involves the picking up and blowing away of loose fine grained material within the soil. Damage from wind erosion is of numerous types. The dust storms resulting therefrom are very disagreeable and the land is robbed of its long-term productivity. Crop damage, particularly in the seedling stage, by blowing soil is often a major concern. Serious stand and subsequent yield and quality losses are incurred and, in the extreme, tender seedlings may be completely killed. Often, sufficient soil is removed to expose the plant roots or ungerminated seed, and this results in complete crop failure. Covering of established crops or pasturage by drifting soil is another common result. These are but a few of the more evident results of wind erosion. The most serious and significant by far, however, is the change in soil texture caused by wind erosion. Finer soil fractions (silt, clay, and organic matter) are removed and carried away by the wind, leaving the coarser fractions behind. This sorting action not only removes the most important material from the standpoint of productivity and water retention, but leaves a more sandy, and thus a more erodible, soil than the original.

Successive removals eventually create a soil condition wherein plant growth is minimized and erodibility greatly increased. Control becomes more and more difficult. In the extreme, the sands begin to drift and form unstable dunes which encroach on better surrounding lands. Throughout recorded history, huge agricultural areas have been ruined for further agricultural use in this manner. It is this degradation of soil resources that constitutes the most serious aspect of wind erosion. Areas so affected become totally unsuited for cultivation. Through difficult and expensive reclamation they may provide, at best, limited grazing. Uncontrolled, they become a menace to adjacent productive lands.

Few attempts have been made in the past to assess the extent of damage caused by wind erosion and the annual losses of land and production which have taken place. All countries admit that the problem does exist to varying degrees, but few can provide exact figures on its magnitude. An exception is the statistic from the USA that Saskatchewan farms have 1000 tonnes of topsoil per acre, of which 15 tonnes are lost annually, due to wind erosion.

With the expansion of agricultural production in lesser developed countries in recent years has come fuller appreciation of past damage, and recent surveys indicate that wind erosion is far more widespread than was commonly believed. In the developing world, where firewood is scarce, peasants burn crop residues for cooking fuel. About 60 percent of crop residues in China and 90 percent in Bangladesh are removed and burned. When planting season comes, dry soils simply blow away. Damage results both from the erosion and the consequent dust storms. Countries of South America, North Africa, the Near East, and Asia all report wind erosion in varying degrees.