U4 - Topic 2.1 - Soil Erosion

 Physical Geography (Topic 2.1-Unit 4)

Soil Erosion

‘Soil erosion’ has been defined as the gradual removal of the top soil by running water, wind, glacier, sea-waves, anthropogenic agents and animals.

– Soil erosion is a universal phenomenon.
– According to one estimate about 75, 000 million tonnes of soil is removed by these agents annually.

Types of soil erosion

• Normal erosion: This is caused by the gradual removal of topsoil by natural processes. The rate of erosion is slow.

• Accelerated erosion: This is caused by manmade activities. In this case, the rate of erosion is much faster than the rate of formation of soil.

Causes of soil Erosion

• Running water:
a) Uniform removal of soil
b) Rill erosion
c) Gully erosion (e.g. northern Punjab, Haryana, Rajasthan, M.P. U.P)

• Wind Erosion: Mainly in the arid and semi -arid regions.
• Anthropogenic factors: Farmland can be degraded in several other ways besides erosion. Physical degradation from mechanical tilling can lead to compaction and crusting. Repeated cropping without sufficient fallow periods or replacement of nutrients with cover crops, manure or fertilizer can deplete soil nutrients. In addition over application of chemical fertilizers, insecticides and pesticides can kill beneficial soil organism.

– Poor water management on irrigated crop land is a leading cause of degraded farmland.
– Inadequate drainage can lead to water logging of the soil or to Salinization, in which salt levels built up in the soil to toxic levels. About 15 to 20 percent of the irrigated land is suffering from some degree of waterlogging and salinization.

• Biotic agents: Overgrazing, mining and deforestation are the major biotic agents causing soil erosion. These processes disturb the top soil thereby exposing the soil to various physical forces inducing erosion.
• Landslides cause soil erosion: Construction of dams, buildings and roads removes the protective vegetal cover leading to soil erosion.

Harmful Effects of Soil Erosion

• Loss of fertile top soil leading to gradual loss of soil fertility and agricultural productivity.

• Loss of mineral nutrients from soil through leaching and flooding.

• Loss of soil ability to hold water and sediment

• Sediment runoff can pollute water courses and kill aquatic life

• Lowering of the underground water table and decrease in the percentage of soil moisture.

• Drying of vegetation and extension of arid lands.

• Increase in frequency of droughts and floods.

• Silting of river and canal belts.

• Recurrence of landslides.

• Adverse effect on economic prosperity and cultural development.

Soil Conservation

Unchecked soil erosion leads to poverty and reduces the strength of a nation. Some of the important steps for soil conservation areas under:

• Conservational till farming or no-till farming: Traditionally, land is ploughed to make a planting surface. This disturbs the soil and makes it susceptible to erosion. The no-till farming method makes minimum disturbance to the top soil by making slits in the unploughed soil. Seeds, fertilizers and water are injected in these slits.

• Contour farming: In this method, crops are planted in rows along contours of gently sloped land. Each row acts as a small dam to hold soil thereby slowing water runoff.
• Terracing: In this method, steep slopes are converted into a series of broad terraces that run across the contour. This retains water for crops and reduces soil erosion by controlling runoff.
• Alley cropping or Agro forestry: This method involves planting crops in strips or alleys between rows of trees or shrubs that provide fruits and fuel wood. Hence, when the crop is harvested, the soil will not be eroded as the trees and shrubs remain on ground holding the soil particles.
• Wind breaks or shelter belts: In this technique, trees are planted in long rows along the boundary of cultivated land which block the wind and reduce soil erosion. Wind breaks help in retaining soil moisture, supply wood for fuel and provide habitat for birds.

Soil health card scheme

• SHC is a printed report that a farmer will be handed over for each of his holdings.

• It will contain the status of his soil with respect to 12 parameters, namely N,P,K (Macro-nutrients) ; S (Secondary- nutrient); Zn, Fe, Cu, Mn, Bo (Micro – nutrients); and pH, EC, OC (Physical parameters).

• Based on this, the SHC will also indicate fertilizer recommendations and soil amendment required for the farm.

• Further, it will advise the farmer on the fertilizers and their quantities he should apply, and also the soil amendments that he should undertake, so as to realize optimal yields.

• It will be made available once in a cycle of 3 years, which will indicate the status of soil health of a farmer’s holding for that particular period.

• Soil samples will be drawn in a grid of 2.5 ha in irrigated area and 10 ha in rain- fed area with the help of GPS tools and revenue maps.

• This initiative will help in improving the soil fertility as the fertilizers and other parameters will be placed according to the need.