Erosion- Factors Affecting Soil Erosion
The factors that influence erosion are:
1. The amount and intensity of rainfall and wind velocity.
2. Topography with special reference to slope of land.
3. Physical and chemical properties of soil.
4. Ground cover its nature and extent.
Soil erosion is the wearing away detachment and transportation of soil from one place and its deposition at another place by moving water blowing wind or any other cause.
1. The amount and intensity of rainfall and wind velocity: Rainfall is the most forceful factor causing erosion through splash and excessive run off.
Rain drop erosion is splash, which results from the impact of water drops, directly on soil. Although the impact of rain drops on water in shallow streams may not splash soil, it does cause turbulence, providing a greater sediment carrying capacity. Large drop may increase the sediment carrying capacity of run off as much as 12 times.
If rain falls gently, it will enter the soil where it strikes and some will slowly run off, but if it occurs in torrents, as usually the monsoon rains doe, there is not enough time for the water to soak through the soil and it runs off causing erosion. Run off that causes erosion, therefore, depends upon intensity, duration, amount and frequency of rainfall. It is observed that rains in excess of 5 cm. per day always caused run off whereas those below 1.25 cm. usually do not.
(The results of soil and runoff losses from air dry deep black and later tic soils with 2 p.e., slope under a rainfall simulator with a constant rainfall immensity of 8.75 cm. per hour indicate that soil loss per 2.5 cm. of siuautated ram) in case of latertic soil is 0.25 tons per hectare. Thus the soil loss in case of deep black soil which is heavier than latertic soil is ten times more.
2. Topography will special reference to slope of lands: Slope accelerates erosion as it increases the velocity of flowing water. Small differences in slope make big difference in damage. According to the laws of hydraulics, a four – time increase in slope doubles the velocity of flowing water. This doubled velocity can increase the erosive power four times and the carrying capacity by 32 times. In one of the experiments in United States of America, it was observed that the loss of soil per hectare due to erosion in a maize plot was 12 tons when the slope was 5 p.c., but it was as high as 44.5 tons under 9 p.c., slope.
3. Physical and chemical properties of soil: Some soils erode more readily than other under the same conditions. The crodibility of the soil is influenced by its texture, structure, and organic matter, nature of day and the amount and kind of salts present. There is less erosion in sandy soil because water is absorbed readily due to high permeability. More organic manure in the soil improves granular structure and water holding capacity. As organic matter decreases, the crodibility of soil increases. Fine textured and alkaline soils are more crodible.
In general, soil detachability increases as the size of the particle increases but soil transportability increases with the decrease in particle size. Clay particles are more difficult to detach than sand, but are easily transported on a level land and much more rapidly on slopes.
4. Ground cover, its nature and extent: The presence of vegetation ground cover retards erosion. Forests and grasses are more effective in providing cover than cultivated crops. Vegetation intercepts the erosive beating action of falling raindrops retards the amount and velocity of surface fun off, permits more water flow into the soil and creates more storage capacity in the soil. It is the lack of vegetation that creates erosion permitting condition.