What is wind erosion?
Wind erosion is the transportation and deposition of soil by the wind. It is a common, natural (and important) phenomenon occurring mostly in dry, sandy soils or anywhere the soil is loose, dry, and finely granulated.
What are the wind erosion processes?
Wind erosion consists of three distinct processes:
- Initiation of the soil particle movement through detachment or deflation which is closely related to soil type and surface condition. The quantity of soil movement depends on the particle size, the cloddiness of particles, aerodynamic roughness, and wind velocity itself.
- Soil particle transportation through suspension, saltation, and surface creep. Sediment transport occurs when soil particles are lifted by airflow and moved along at various heights above the surface of the ground, often colliding with other particles. Depending on the size weight of the soil particles, the energy required to loosen and transport particles varies, with stronger winds carrying heavier particles.
- Deposition of soil particles happens when eventually the wind velocity decreases, and soil particles are deposited. In-field deposition typically occurs in furrows or vegetated areas. The deposition also occurs along the edge of fields in ditches, fence rows, vegetation or barriers such as windbreaks.
What are the common wind erosion control methods?
Wind erosion is controlled by reducing the wind erosion forces on erodible soil particles and/or by creating aggregates or soil surfaces more resistant to wind erosion forces. This can be accomplished by reducing field width, maintaining vegetation cover on the soil surface, utilizing stable soil aggregates, roughing the land surface to reduce wind velocity and trap drifting soil and levelling the land to reduce erosion rates on slopes and hilltops. Let us unpack wind erosion control methods whilst giving a list of bullet points of all methods and a detailed explanation of each.
- Windbreaks, wind barriers and shelterbelts – contribute to wind erosion control by reducing wind speed on their leeward side below the threshold required for initiation of soil movement and by decreasing the field length along the erosive wind direction. The effect of any barrier in reducing the rate of soil movement depends on the wind velocity and direction, the threshold velocities needed to initiate soil movement, and the barrier shape, width, height and porosity.
- Annual and perennial grass barriers – perennial grass barriers have worked well for controlling wind erosion, trapping snow and reducing evaporation on dryland cropping areas. Annual crops are sometimes interplanted in narrow strips or row so one crop provides protection to the other crop or unprotected fallow field.
- Polymeric emulsions – these are non-vegetative covers mainly but not exclusively used on non-agricultural land where it is not feasible to obtain cover by growing and managing vegetation. Polymeric emulsions stabilize soil against wind erosion by forming a (1) surface crust that indispersible in water, durable yet porous enough to allow percolation of water, (2) weak enough for seedling penetration (3) must be able to maintain their sticky property indefinitely when used as permanent wind erosion control covers (4) must be easy to apply.
- Artificial barriers – only a very limited basis snow fencing, board walls, bamboo and willow fences, earthen banks, hand-inserted straw rows and rock walls have been used for wind erosion control. There is usually a very high cost in material and labor to construct these barriers and their use is generally restricted to high-value crops. They can also be used in sand dune areas to aid the initial stabilization of the area while grass and trees are being established.
- Strip cropping – this is dividing a large field into strips that are narrow enough to help control wind erosion. Usually strips of erosion-resistant crops or standing stubble are alternated with other crops or unprotected fallow fields. Strip cropping reduces the downwind avalanching effect of wind erosion and is a very effective erosion control method.
- No tillage – no till is a procedure whereby a crop is planted directly into a seedbed that has not been tilled since harvest of the previous crop. Only the immediate seed zone is disturbed, and no additional tillage occurs. Reducing the number of tillage operations between harvest and planting of the next crop is an important step toward decreasing soil erosion.
- Cover crops – the main objective of cover crop is to produce vegetative protection for the land against wind and water erosion. Cover crops are usually planted when protective residues are inadequate, and winter and spring winds are high. They are planted between rows to provide protection against high susceptibility to abrasive injury in the seedling stage.
- Roughening the land surface – soil surface roughness consists of anchored vegetative material, soil ridges, soil clods, or combinations of all three. These all help to control wind erosion by lowering the wind velocity near the soil surface and by sheltering erodible soil fractions.
- Emergency tillage – it is a last resort wind erosion control practice than can provide a rough, cloddy surface. This is usually carried out when vegetative cover is depleted by excessive grazing, drought, improper or excessive tillage or by growing crops that produce little or no residue. Emergency tillage should be done before blowing starts since soils rapidly become more erodible under the abrasion of moving particles, thus requiring even more drastic measures to prevent further erosion.
- Geosynthetic erosion control products – a geosynthetic provides containment when it encapsulates or surrounds materials such as sand, rocks, and straw. Examples include natural fiber mulches, geotextile filters, erosion control netting, riprap, erosion control blankets and open weave meshes. These products provide different properties to the soil which include vegetative density, good moisture absorption, flexibility over differential settlement and good sediment yields.
One is spoilt for choice when it comes to the selection of wind erosion control methods. As depicted by the article the application of each method now depends on the intended outcomes of the wind erosion control plan which should also factor in the why and how it should be done. Wind erosion should be prevented because it reduces soil productivity, increases the generation of dust, clogs streams and drainage channels, buries plants and blocks sunlight.
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