SOIL IN INDIA

(CLASS 10) SOIL EROSION:

Soil erosion is a gradual process that occurs when the impact of water or wind detaches and removes soil particles, causing the soil to

deteriorate. Soil deterioration and low water quality due to erosion and surface runoff have become severe problems worldwide. The

problem may become so severe that the land can no longer be cultivated and must be abandoned. Many agricultural civilizations have

declined due to land and natural resource mismanagement, and the history of such civilizations is a good reminder to protect our

natural resources.

Erosion is a serious problem for productive agricultural land and for water quality concerns. Controlling the sediment must be an

integral part of any soil management system to improve water and soil quality. Eroded topsoil can be transported by wind or w ater into

streams and other waterways. Sediment is a product of land erosion and derives largely from sheet and rill erosion from upland areas,

and to a lesser degree, from cyclic erosion activity in gullies and drainageways.

The impact of soil erosion on water quality becomes significant, particularly as soil surface runoff. Sediment production and soil erosion

are closely related. Therefore, the most effective way to minimize sediment production is the stabilization of the sediment s ource by

controlling erosion. Several conservation practices can be used to control erosion but first you need to understand the factors affecting

soil erosion. Soil erosion is the detachment and movement of soil particles from the point of origination through the action of water or

wind. Thus, minimizing the impact of water or wind forces is the main objective for erosion control. Water erosion is the mos t pertinent

erosion problem in Iowa.

Soil erosion by water occurs when bare-sloped soil surface is exposed to rainfall, and the rainfall intensity exceeds the rate of soil

intake, or infiltration rate, leading to soil-surface runoff. Soil erosion can occur in two stages: 1) detachment of soil particles by raindrop

impact, splash, or flowing water; and 2) transport of detached particles by splash or flowing water. Therefore, soil erosion is a physical

process requiring energy, and its control requires certain measures to dissipate this energy.

The hydrologic processes of rainfall and runoff play an essential role in water erosion. The amount and rate of surface runoff can affect

erosion and sediment transport. Thus, soil conservation practices are important in reducing soil erosion. Improving the soil infiltration

rate, resulting in less surface runoff, can lead to reduction of soil erosion. Agronomic, cultural, or structural practices are available

CAUSES FOR SOIL EROSION

The agents of soil erosion are the same as the agents of all types of

erosion: water, wind, ice, or gravity. Running water is the leading cause of soil erosion, because water is

abundant and has a lot of power. Wind is also a leading cause of soil erosion because wind can pick up soil and

blow it far away.Activities that remove vegetation, disturb the ground, or allow the ground to dry are activities

that increase erosion. What are some human activities that increase the likelihood that soil will be eroded?

Farming

Agriculture is probably the most significant activity that accelerates soil erosion because of the amount of land

that is farmed and how much farming practices disturb the ground (Figure 1). Farmers remove native vegetation

and then plow the land to plant new seeds. Because most crops grow only in spring and summer, the land lies

fallow during the winter. Of course, winter is also the stormy season in many locations, so wind and rain are

available to wash soil away. Tractor tires make deep grooves, which are natural pathways for water..

Grazing

Grazing animals (Figure 2) wander over large areas of pasture or natural grasslands eating grasses and shrubs.

Grazers expose soil by removing the plant cover for an area. They also churn up the ground with their hooves. If

too many animals graze the same land area, the animals’ hooves pull plants out by their roots. A land is

overgrazed if too many animals are living there.

Construction

Constructing buildings and roads churns up the ground and exposes soil to erosion. In some locations, native

landscapes, such as forest and grassland, are cleared, exposing the surface to erosion (in some locations the

land that will be built on is farmland). Near construction sites, dirt, picked up by the wind, is often in the air.

Completed construction can also contribute to erosion

LOGGING AND MINING

Logging removes trees that protect the ground from soil erosion. The tree roots hold the soil together and the

tree canopy protects the soil from hard falling rain. Logging results in the loss of leaf litter, or dead leaves, bark,

and branches on the forest floor. Leaf litter plays an important role in protecting forest soils from erosion.

TYPES OF SOIL EROSION: Sheet and rill erosion

Hill slopes are prone to sheet erosion and rill erosion. The amount of hill slope erosion largely depends on how the

land is used.Sheet erosion occurs when a thin layer of topsoil is removed over a whole hillside paddock—and may

not be readily noticed.Rill erosion occurs when runoff water forms small channels as it concentrates down a slope.

These rills can be up to 0.3m deep. If they become any deeper than 0.3m they are referred to as gully erosion.

Gully erosion

Gully erosion happens when runoff concentrates and flows strongly enough to detach and move soil particles.For

example, a waterfall may form, with runoff picking up energy as it plunges over the gully head. Splashback at the

base of the gully head erodes the subsoil and the gully eats its way up the slope.Gullies may develop in

watercourses or other places where runoff concentrates. In cultivation or pastures, advanced rill erosion can

develop into gully erosion.deep alluvial and colluvial soils.

Stream bank erosion

Recent floods have made stream bank erosion a widespread problem across Queensland.The major cause of

stream bank erosion is the destruction of vegetation on river banks (generally by clearing, overgrazing, cultivation,

vehicle traffic up and down banks or fire) and the removal of sand and gravel from the stream bed.

Tunnel erosion

Tunnel erosion is the removal of subsoil.

When water penetrates through a soil crack or a hole where a root has decayed, the soil disperses and is carried

away with the flow to leave a small tunnel.Initially, the surface soil remains relatively intact but, with every flow,

the tunnel becomes larger and the soil may eventually collapse and form a gully.The whole process speeds up

significantly if an outlet is provided (such as an existing gully or cutting in a roadside) as this allows free flow of

subsurface drainage water.

EFFECT OF SOIL EROSION A major problem with soil erosion is that there is no telling how quickly or slowly it will occur. If largely impacted

by ongoing weather or climate events, it may be a slow-developing process that is never even noticed.

However, a severe weather occurrence or other experience can contribute to rapid-moving erosion, which can

cause great harm to the area and its inhabitants.

Some of the greatest effects of soil erosion include:

• Loss of topsoil: Obviously, this is the biggest effect of soil erosion. Because topsoil is so fertile, if it is

removed, this can cause serious harm to farmer’s crops or the ability to effectively work their land.

• Soil compaction: When the soil under the topsoil becomes compacted and stiff, it reduces the ability for

water to infiltrate these deeper levels, keeping runoff at greater levels, which increases the risk of more

serious erosion.

• Reduced organic and fertile matter: As mentioned, removing topsoil that is heavy with organic matter

will reduce the ability for the land to regenerate new flora or crops. When new crops or plants can’t be

placed successfully in the area, this perpetuates a cycle of reduced levels of organic nutrients.

• Poor drainage: Sometimes too much compaction with sand can lead to an effective crust that seals in the

surface layer, making it even harder for water to pass through to deeper layers. In some ways, this can

help erosion because of the densely packed soil, but if it perpetuates greater levels of runoff from

rainwater or flooding, it can negatively impact the crucial topsoil.

• Issues with plant reproduction: When soil is eroded in active cropland, wind, in particular, makes lighter

soil properties such as new seeds and seedlings to be buried or destroyed. This, in turn, impacts future

crop production.

• Soil acidity levels: When the structure of the soil becomes compromised, and organic matter is greatly

reduced, there is a higher chance of increased soil acidity, which will significantly impact the ability for

plants and crops to grow.

• Long term erosion: Unfortunately, if an area is prone to erosion or has a history of it, it becomes even

harder to protect it in the future. The process has already reduced the soil structure and organic matter

of the area, meaning that it will be harder to recover in the long run.

Water pollution: A major problem with runoff from soils – particularly those used for agricultural processes – is

that there is a greater likelihood that sediment and contamination like the use of fertilizer or pesticide. This can

have significant damage on fish and water quality

SOIL CONSEVATION

What is Soil Conservation?

Soil Conservation is the name given to a handful of techniques aimed at preserving the soil. Soil loss

and loss of soil fertility can be traced back to a number of causes including over-use, erosion,

salinization, and chemical contamination. Unsustainable subsistence farming and the slash and burn

clearing methods used in some less developed regions can often cause deforestation, loss of soil

nutrients, erosion on a massive scale, and sometimes even complete desertification.

Soil erosion removes the topsoil that is necessary for organic matter, nutrients, micro-organisms that

are required for plants to grow and shine. Soil conservation is one such step that protects the soil

from being washed away. The soil then ends up in aquatic resources bringing in pesticides and

fertilizers used on agricultural land. Effective control of soil erosion by water consists of minimizing

the impact of raindrops and the velocity of running water on the soil surface. This task includes

enhancing infiltrability and surface storage, improving soil structure, protecting the topsoil by a cover

crop or a mulch of organic residues (e.g., straw) to prevent raindrops from striking the bare surface,

minimizing cultivation and performing it on the contour rather than up and down the slope, and

avoiding both compaction and excessive soil pulverization. An ancient and still common practice

of soil conservation is the shaping of sloping land by means of terraces or contour strips to reduce the

inclination of the surface and the length of slope segment, thereby checking the downhill acceleration

of running water.

Control of wind erosion can be achieved by means of shelter belts, which are parallel rows of trees or

shrubs planted in a direction perpendicular to the prevailing direction of the wind. Additional

measures are ensuring the presence of a protective vegetative cover or a mulch on the soil surface to

keep it from the direct action of wind; keeping the topsoil in a cloddy rather than dusty or excessively

pulverized state; enhancing soil aggregation by organic-matter enrichment; and maintaining the

topsoil in a moist condition by evaporation control and, where possible, by light irrigation.

METHODES OF SOIL CONSERVATION Many different techniques have been invented throughout the years with the aim of preserving the nutrient level

of the soil and preventing erosion.

1. Contour Plowing

Originating in ancient Phoenicia, Contour Plowing involves plowing grooves into the desired farmland, then

planting the crop furrows in the grooves and following the contours. It a very effective way for farmland on slopes

to prevent runoff improve crop yields.

2. Terrace Farming

Terracing is a method of carving multiple, flat leveled areas into hills. Steps are formed by the terraces which are

surrounded by a mud wall to prevent runoff and hold the soil nutrients in the beds.

More commonly found in lesser developed nations due to the difficulty of using mechanized farming equipment in

the terraces. Very popular in Asia for planting rice.

3. Keyline Design

A more enhanced version of Contour Plowing, maximum water retention is achieved by taking into account all the

watershed properties when making the contour lines.

The Keyline refers to topographic features linked to water flow. This allows the water to run off to run directly into

an existing water channel, and prevent soil erosion caused by the water.

4. Perimeter Runoff Control

This is the practice of planting trees, shrubs, and ground cover around the perimeter of your farmland which

impedes surface flows and keeps nutrients in the farmed soil. Using the grass way is a specialized way of handling

perimeter runoff that uses surface friction to channel and dissipate runoff.

5. Windbreaks

Rows of tall trees are used in dense patterns around the farmland and prevent wind erosion. Evergreen trees can

provide year-round protection but deciduous trees can be adequate as long as foliage is apparent during the

seasons when the soil is bare.

6. Cover Crops/ Crop Rotation

Cover crops such as turnips and radishes are rotated with cash crops in order to blanket the soil all year- round

and produce green manure the replenishes nitrogen and other critical nutrients. Using cover crops can also

suppress weeds.

7. Soil Conservation Farming

A mixture of farming methods intending the mimic the biology of virgin land. These practices can be used to

prevent erosion and even restore damaged soil and encourage plant growth.

Eliminating the use of nitrogen fertilizer and fungicides can increase yields and protect crops from drought and

flooding.

8. Agrostological Measures

Planting grass in heavily eroded areas is called an agrostological measure. Ley farming practices cultivating grass

in rotation with regular crops to increase the nutrient level in the soils.

When the grass is harvested it can be used as fodder for cattle. For heavily eroded soil it is recommended to

grown grass for many years to let the soils naturally repair themselves.

09. Green Manures

Green manures are a few different crops that can be grown, not for produce or food usage, but grown in order to

fertilize the farmland on which it grows. This method can improve the soil structure and suppresses the growth of

weeds.

10. Stream Bank Protection

During floods, stream banks can often cave in. Preventing this by constructing walls along the banks or plant

useful tree species will prevent this in the future and prevent soil loss down the stream.

11. Earthworms

Earthworms provide great benefits of farmland due to the way they burrow under the ground and provide more

are for water to rest after it has infiltrated the soil. When these worms excrete egesta, this sits in the soils and

gives the crops many nutrients which are absorbed via the roots of the plants.

Earthworm casts contain a vast amount more nutrients than any natural soil in the world, and for that reason

should be invited into the soils of farmland to help prevent erosion and will lead to larger crop yields.

12. Prevent Overgrazing

Try not to let overgrazing happen by moving herds around often. If overgrazing occurs, plant hardier and more

nutritious species of forage in order to rebuild the soil. You can also harvest these crops and feed them to the

grazers during the winter season.

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