Soil Profile – Soil Management
Soil Profile – Soil Management
Soil consists of three major layers which are called horizons namely, A, B and C horizons. Apart from these three layers, some other layers might be present at some locations.
Moving from the top to bottom, various soil horizons include the following:
- Horizon O: It is a surface horizon that is comprised of organic materials at various stages of decomposition. It is the most prominent in forested areas, where there is accumulation of debris fallen from trees.
- Horizon A: It is a surface horizon that largely consists of minerals (sand, silt and clay) and with appreciable amounts of organic matter. The organic materials get incorporated with the mineral matter, nutrients and water, which are necessary for the growth of plants. This horizon is predominantly the surface layer of many soils in grasslands and agricultural lands.
- Horizon E: It is a subsurface horizon that has been heavily leached. Leaching is the process in which soluble nutrients are lost from the soil due to precipitation or irrigation. The horizon is typically light in colour. This is not present in all soils.
- Horizon B: It is a subsurface horizon that has accumulated from the deposition of certain minerals that have leached from the layer(s) above. ‘Horizon B’ is a transition zone between ‘Horizon A’ and ‘Horizon C’, and contains matter derived from below as well as from above. It has some organic matter in it, although the mineral matter is noticeably weathered.
- Horizon C: It is the least weathered horizon. It is an unconsolidated, loose parent material. This layer is the first stage in the soil formation process.
- Horizon R: Underneath the above mentioned soil horizons is the rock which is also known as the parent rock or the bedrock. The horizon containing the bedrock is known as Horizon R. This arrangement of layers is known as the soil profile.
Soil Degradation and Soil Erosion
- The decline in soil fertility is called soil degradation. The degree of soil degradation varies from place to place according to the topography, wind velocity and amount of rainfall.
- Soil degradation can be due to multiple reasons.
- Use of chemical fertilisers in the absence of organic manure is also harmful to the soil. Unless the soil gets enough humus, chemicals harden it and reduce its fertility in the long run.
- In the areas of excessive use of irrigation without adequate rainfall, the fertile soils become saline. The excessive irrigation depletes the underground water level. Moreover, the water used in the field evaporates, leaving the salts behind.
- These salts fill the small holes through which underground water is recharged. This process is known as soil salinity. Soil salinity further leads to desertification of land.
- The destruction of the soil cover is described as soil erosion. The soil forming processes and the erosional processes of running water and wind go on simultaneously.
- But generally, there is a balance between these two processes. The rate of removal of the fine particles from the surface is the same as the rate of addition of particles to the soil layer.
Various types of soil erosions include the following:
- Wind erosion: It is significant in arid and semi-arid regions.
- Water erosion: In regions with heavy rainfall and steep slopes, erosion by running water is common and it takes place mainly in the form of sheet or gully erosion.
- Sheet erosion: It takes place on level lands after a heavy shower and the soil removal is not easily noticeable. However, it is harmful since it removes the finer and more fertile top soil.
- Gully erosion: It is common on steep slopes. Gullies deepen with rainfall, cut the agricultural lands into small fragments and make them unfit for cultivation. A region with a large number of deep gullies or ravines is called badland topography. Ravines are widespread in the Chambal Basin. Besides this, they are also found in Tamil Nadu and West Bengal.
Various techniques used for soil conservation are listed below:
- In agriculture, a terrace is a piece of sloped plane that has been cut into a series of successively receding flat surfaces or platforms, which resemble steps, for the purposes of more effective farming. This type of landscaping is called terracing. Soil Profile – Soil Management
- Graduated terrace steps are commonly used to farm on hilly or mountainous terrain. Terraced fields decrease both the erosion of soil and surface runoff of water.
- Contour ploughing or contour farming or contour bunding is the farming practice of creating a water break along the contour lines.
- The water break reduces heavy water runoff, which is a major cause of soil erosion. The water break also allows more time for the water to settle into the soil.
- A check dam is a small dam constructed across the waterway to counteract erosion by reducing the velocity of water flow.
- Check dam is not a type of new technology; rather, it is an ancient technique.
- A wind break (shelter belt) is usually made up of one or more rows of trees or shrubs, planted in such a manner so as to provide shelter from the wind and to protect soil from erosion.
- Wind breaks commonly planted around the edges on the farms. Soil Profile – Soil Management
- If designed properly, windbreaks around a home can reduce the cost of heating and cooling. Wind breaks are also planted to prevent snow from drifting onto roadways.