Chapter: Environmental Science and Engineering

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Land Resources

Soil is the mixture of inorganic materials (rocks and minerals) and organic materials (dead animals and plants).

LAND RESOURCES

It provides food, fibre, wood, medicine and other biological materials

 

Soil is the mixture of inorganic materials (rocks and minerals) and organic materials (dead animals and plants).

 

Top soil is classified as renewable resources.

 

Uses of land resources

Land provide, food, wood, minerals, etc., for us

 

Land nurtures the plants and animals that provide our food and shelter.

Land is used as watershed or reservoir

Land acts as a dust bin for most of the wastes, created by the modern society.

Land is used for construction of buildings, industries.

 

1 LAND DEGRADATION

Process of degradation of soil or loss of fertility of the soil.

 

Harmful effects of land degradation

The soil texture and soil structure are deteriorated

 

Loss of soil fertility, due to loss of invaluable nutrients

 

Increase in water logging, salinity, and alkalinity and acidity problems.

Loss of economic social and biodiversity.

 

Causes of land degradation 3. Population

Land resources degraded by over population &over exploitation.

 

2. Urbanization

Urbanization leads to deforestation, reduces the land

 

3.  Fertilizers and pesticides

 

Increased applications of fertilizers and pesticides leads to pollution of land and water and soil degradation.

 

4. Damage of top soil

 

Increase in food production generally leads to damage to top soil through nutrient depletion.

 

5.  Water-logging

Soil erosion, salination and contamination of the soil with industrial wastes all cause land degradation.

 

6.  Soil erosion

Soil erosion is the process of removal of superficial layer of the soil from one place to another.

 

Harmful effects of soil erosion

 

Soil fertility is lost because of loss of top soil layer.

Loss of its ability to hold water and sediment.

Sediment runoff can pollute water and kill aquatic life.

 

Types of soil erosion

 

(i)Normal erosion

Gradual removal of top soil by the natural process.

 

The rate of erosion is slower.

 

(ii)Accelerated erosion

Caused by man-made activities

 

The rate of erosion is much faster than the rate of formation of soil.

 

Man induced landslides

 

Various anthropogenic activities like hydroelectric projects, large dams, reservoirs, construction of roads and railway lines, construction of buildings, mining etc are responsible for clearing of large forested areas.

 

Earlier there were few reports of landslides between Rishikesh and Byasi on Badrinath Highway area. But, after the highway was constructed, 15 landslides occurred in a single year.

 

During the construction of roads, mining activities etc. huge portions of fragile mountainous areas are cut or destroyed by dynamite and thrown into adjacent valleys and streams.

 

These land masses weaken the already fragile mountain slopes and lead to landslides.

They also increase the turbidity of various nearby streams, thereby reducing their productivity.

 

Causes of soil erosion (i)Water

Affects soil erosion in the form of rain, run-off, rapid flow, wave action.

 

Sheet erosion: When there is uniform removal of a thin layer of soil from a large surface area, it is called sheet erosion.

 

Rill erosion: when there is rainfall and rapidly running water produces finger-shaped grooves or rills over the area, it is called rill erosion.

 

Gully erosion: When the rainfall is very heavy, deeper cavities or gullies are formed, which may be U or V shaped.

 

Slip erosion: This occurs due to heavy rainfall on slopes of hills and mountains.

 

Stream bank erosion: During the rainy season, when fast running streams take a turn in some other direction, they cut the soil and make caves in the bank.

 

(ii)Wind

 

Wind is the important climatic agent, who carry away the fine particles of soil and creates soil erosion. Saltation: This occurs under the influence of direct pressure of stormy wind and the soil particles of 1-3.5 mm diameter move up in vertical direction.

 

Suspension: Here fine soil particles (less than 1mm diameter) which are suspended on the air are kicked up and taken away to distant places.

 

Surface creep: Here the large particles (5-10 mm diameter) creep over the soil surface along with wind.

 

(iii)Biotic agents

 

Overgrazing, mining and deforestation are the major biotic agents, cause soil erosion. Deforestation without reforestation, overgrazing by cattle, surface mining without land reclamation, irrigation techniques that lead to salt build- up, water logged soil, make the top soil vulnerable to erosion.

 

.

35% of world soil erosion is due to overgrazing.

30% of world soil erosion is due to deforestation.

 

(iv) Landslides

 

-Causes soil erosion.

(v)Construction

 

-Construction of dams, buildings, roads removes the protective vegetal cover and leads to soil erosion.

 

Control of soil erosion (or) soil conservation practices

.

 

3. Conservational till farming (or) no-till-farming

 

In tradition method, the land is ploughed and soil is broken up and leveled to make a planting surface. This disturbs the soil and makes it susceptible to erosion

 

However, no-till-farming causes minimum disturbance to the top soil

 

Here the tilling machines make slits in the unploughed soil and inject seeds, fertilizers and water in the slit. So the seed germinates and the crop grows.

 

2. Contour farming

It involves planting crops in rows across the contour of gently sloped land.

Each row acts as a small dam to hold soil and to slow water runoff.


3. Terracing

 

It involves conversion of steep slopes into broad terraces, which run across the contour. This retains water for crops and reduces soil erosion by controlling runoff.



4. Alley cropping (or) Agro forestry

 

It involves planting crops in strips or alleys between rows of trees of shrubs that can provide fruits and fuel wood.

 

Even when the crop is harvested, the soil will not be eroded because trees and shrubs still remain on the soil and hold the soil particles.



5. Wind breaks or shelter belts

 

The trees are planted in long rows along the boundary of cultivated lands, which block the wind and reduce soil erosion.

 

Wind breaks help in retaining soil moisture, supply of some wood for fuel and provide habitats for birds.




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