Need for Soil Conservation and Types of Soil Erosion
The basic requirements of any human being are food, shelter and clothing. All these three items are related to soil in one way or the other. Soil conservation thus plays a very important role in preventing erosion of soil. Some practical methods of soil conservation and the management of soil erosion are discussed herein.
Soil is a precious gift of nature. It is a mixture of rocks, minerals, and the decayed matter of plants and animals. The solid soil particles are interspersed with air and water. It takes a long time to form a small layer of soil- say as long as a thousand years per inch. The formation of soil is due to physical weathering and chemical weathering.
All resources such as soil, water, forests, minerals, etc. need proper and efficient use. Soil is directly related to the health of an individual and indirectly to the health of a nation. The fertility of soils can be improved, but the building up of soil takes a very long time.
Experience and observations have shown that crops from poorly managed soils do not possess the same nutritive value as those obtained from land in which sufficient quantity of minerals are available.
Agriculture had its beginning minimum 7000 years ago and developed in the fertile plains of Mesopotamia and the valley of the Nile. The irrigation canals in Babylon were filled with silt resulting in once irrigated lands turning into dry lands and finally caused the ruin of the country itself.
Erosion is the detachment and transportation of soil. The main agent for transportation is running water. To a certain extent wind, sea waves, and moving ice may also cause erosion.
Soil erosion may be "natural" or "accelerated." The heat of the sun, rain drops, wind blasts, the roots of the plants and trees- all are acting upon the crust of the earth resulting in physical, chemical, and biological changes. This natural process has been going on for as long as the world has existed. When man appeared on the scene and started abusing nature, the situation changed. He started to fell trees, cut grasses, and rip up the land for cultivation, all to meet his daily needs. This detachment and transportation of soil is called accelerated soil erosion. It is entirely a man-made condition.
Methods for Soil Conservation
Soil conservation is the management of the soil to prevent soil erosion. Soil conservation not only increases crop yields, but also prevents further deterioration of land. Methods to control surface rub-off and thereby preventing soil erosion have been practiced from time immemorial. There are different methods and systems for conservation depending on the type of soil and past experience of the experts in this field.
Contour bunding is the construction of small bunds across the slope of the land on a contour so that the long slope is cut into a series of small ones and each contour bund acts as a barrier to the flow of water. Bunds are constructed with materials taken from borrow pits in the vicinity.
Terracing is done on sloping lands. By intercepting the surface run-off before it attains sufficient velocity to erode the soil, terraces reduce soil and water loss, and prevent formation of gullies. From a functional point of view, terraces can be classified as 1) drainage type, 2) absorptive type.
Biological methods of soil conservation
Contour bunding, terracing, etc. are mechanical means of controlling erosion. Control of erosion through crops or vegetation is a biological method of conservation. Some of the methods are mixed cropping, improved soil and crop management practices, contouring, and the cropping system.
Forestry in soil conservation
A dense cover of vegetation is the most powerful protection against erosion. Trees and plants also help in soil conservation. Forests can be raised and maintained both naturally and artificially. Proper maintenance of the forest is very essential. The following are the important points for preserving our forest wealth: fire protection, regulated and controlled grazing, and regulated felling of trees.
Soil has a very important role to play in the life of human beings. As a part of development and modernization, trees are cut and vegetation is chopped off, leading to large scale erosion. Soil conservation is important at this juncture- the soil has to be preserved and the environment kept neat, tidy, and productive in order to preserve our human health and nutrition.
1.Soil Conservation, MSV Rama Rao,ICAR, New Delhi,1974
2.Classification and reclamation of ravine lands,Tejwani K C,NIS, Indai,1963
3.Soil Mechanics in Engineering Practices, Karl Terzhaghi & R B Peck, Asia Publications, Mumbai, 1948.