After reading this article you will learn about Wind Erosion:- 1. Factors Affecting Wind Erosion 2. Mechanism and Types of Wind Erosion 3. Control.
Factors Affecting Wind Erosion:
Susceptibility to wind erosion is related rather definitely to the moisture content of soils. Wet soils do not blow. Soil erosion by wind occurs under dry conditions and high wind velocity.
Following factors affect soil erosion by wind:
As the soils are loosened by the excess tillage the blowing wind removes finer particles. On an untilled surface wind erosion is very less in comparison to tilled surface.
Soils with single-grained structure (structure less) is more prone to wind erosion than aggregate structure.
3. Organic Matter Content:
Soils with low organic matter have low amounts of water stable aggregate thus facilitating wind erosion.
4. Barren Surface:
The presence of vegetation will reduce wind erosion hazards. This effectively presents a barrier to wind movement. In addition, plant roots help bind the soil and make it less susceptible to wind damage.
5. Continuous Dry Weather:
Continuous dry weather will increase wind erosion because soil particles are loosened due to lack of moisture. In wet and moist soils the finer particles are held together, hence, no danger of soil erosion by wind.
6. Wind Velocity and Turbulence:
Obviously, the rate of wind movement, especially gusts having greater than average velocity, will influence erosion.
Mechanism and Types of Wind Erosion:
The loss of soil by wind movement involves two processes:
(a) Detachment, and
The abrasive action of the wind results in some detachment of tiny soil grains from the granules or clods of which they are a part. When the wind is laden with soil particles, however, its abrasive action is greatly increased. The impact of these rapidly moving grains dislodges other particles from soil clods and aggregates.
The transportation of the particles once they are dislodged takes place in three ways.
The types are:
In saltation soil particles of medium size (0.10-0.15 mm diameter) are carried by wind in a series of short bounces. These bounces are caused by the direct pressure of the wind on soil particles.
(ii) Soil Creep:
Saltation also encourages soil creep (rolling or sliding) along the surface of the large particles (0.5-1.0 mm diameter). The bouncing particles carried by saltation strike the large aggregates and speed up their movement along the surface.
When the particles of soil are very small (less than 0.1 mm) they are carried over long distances. Finer suspended particles are moved parallel to the ground surface and upward.
Control of Wind Erosion:
Principles of Wind Erosion Control:
(i) To reduce the erodibility of the soil.
(ii) To reduce wind velocity at ground level.
The following principles and practices should be adopted for the management of eroded land wind:
1. Conservation of Moisture:
Obviously, if the soil can be kept moist there is little danger of wind erosion. This can be done by ploughing of the lands during rains, leveling, bunding and terracing of the land and water harvest.
2. Vegetative Cover:
A vegetative cover discourages soil blowing by providing a mechanical obstruction to erosive winds thus reducing their velocity and soil carrying capacity. The roots help in binding the soil particles together, in this way they resist erosion by wind.
Stubble mulch has proved to be effective in controlling wind erosion.
4. Rough Surface:
Wind is more effective on smooth surface than on rough surface. Hence, if no mulch is possible then the surface should be left rough during the period of high winds.
5. Trash Tillage:
Tillage operations that leave the clods and trash at the surface and are desirable in controlling wind erosion. The trash should not be buried but mixed with the surface soil so that it is not easily flown away, but will obstruct the movement of the soil in a lose condition and without a good cover is liable to lead heavy wind erosion. Opening ridges and furrows at right angles to the prevailing winds is desirable to a certain extent.
6. Organic Matter:
This is desirable for increasing the stability of the soil structure, for improving water-holding capacity of the soil and for building up its fertility. Using green manure crops is a desirable practice for this purpose. Crop residues should be left on the soil and not removed for use as fuel.
7. Regulating Grazing:
Probably the most important cause of wind erosion is overgrazing. There must be grazing regulations to restrict the use of grazing lands.
8. Strip Cropping:
Strip cropping is an effective method for controlling the wind erosion. Wind strip cropping, one of the types of strip cropping is especially suitable for the land which is susceptible to wind erosion. In wind strip cropping normal crop row should be alternated with tall crop or plant, at right angles to the direction of the prevailing winds.
9. Vegetative Barriers:
To cater the need of small farmers, vegetative barriers (also known as live-funds) for rain water conservation and to regulate overland flows are useful.
Important vegetative barriers are:
Anjan grass (Cenchrusciliaris)
Lemon grass (Cymbopoganflexuosus)
Broom grass (Thysanolaena maxima)
Vegetative barriers have not been widely accepted by the famers. Acceptance can be enhanced by selecting the species which can yield fodder for the cattle or lopping’s to maintain soil fertility (Fig. 23.5).
10. Wind Break and Shelterbelt:
Trees and shrubs, commonly planted in rows at right angles to the prevailing winds are called shelterbelts. A recommended shelterbelt to control wind erosion may be made by planting three rows of trees and shrubs, the control row to consist of tall trees and the two outside rows to consist of smaller dense shrubs.
Example of Tall Trees:
(i) Acacia arabica- Babul
(ii) Dalbergiasisso – Shisham
(iii) Eucalyptus rostrata – Eucalyptus
(iv) Azadirachtaindica -Neem
(v) Albizzialebbek -Siris
Example of Bushy Shrubs:
(i) Cassia auriculata
(v) Zizyphus species.
Stabilizing of Drifting Sand Dunes:
The deposition of sand on cultivated land happens usually in the neighbouring of sand dunes or the tract of blowing sand, from which sand is easily blown on the good cultivated land. The only method by which this can be prevented consists likewise in establishing some soil or and binding vegetation on these dunes.
Suitable grasses, generally with a creeping habit, and trees which can grow in sandy situations have to be planted sand their growth encouraged and the drifting of the sand prevented thereby. The cashew-nut tree and the screw pine are common trees for this purpose. The others sand binding trees are Acacia arabica, Agave americana, Andropogonlaniger etc.