Erosion and Soil Conservation

Soil Erosion:

Soil erosion is the process of the removal of soil particles from the parent body and transportation of such particles by wind or water.

Runoff:

Runoff is the excess water from precipitation that moves out of field and finds its way to river , lakes and oceans 

Runoff= Rainfall - ( infiltration+ Interception+ Surface storage +Surface detention 

Factors Affecting Runoff:

A) Climatic factors :

1) Rainfall Characteristics:

Amount Intensity, Duration and distribution of of rainfall

2) Snowfall

3) Evapo-transpiration 

B) Physiographic Factors:

 1)Watershed characteristics:

Topography of soil , soil types , orientation, Geology, vegetal Cover , shape and size of watershed

2) Channel Characteristics:

Size , shape , cross section and roughness of channel bed

C) Geological Factors:

Rainfall intensity of more than 5cm/hr is considered as severe

Soil Loss Equation due to Water Erosion:

 A= RKLSCP

Where 

A- Predicted soil loss

R - Rainfall and runoff factor 

K- Soil erodibility

L- Slope length

S- Slope gradient or steepness

C- Soil cover and management

P- Erosion control practice

Wind erosion control measures should aim at reducing wind velocity or alteriong soil characteristics

Soil Conservation Measures:

Soil conservation is the preservation of soil against deterioration and loss by using it within its capabilities, and applying the conservation practices needed for its Protection and improvement

Fundamental principles of soil conservation:

a)  Land use based on its capability

b) Conservation of soil and moisture to avoid damage to the soil

c) Use of best soil crop management practices, correction of acidity, alkalinity and drainage

Land Capability Classification:

On  the basis of capability or limitations the lands are grouped into two major groups

A) Lands suitable for Cultivation:

Such lands are used for agriculture or cultivation of crops .

Such land has four classes . These four classes are differentiated on the basis of limitations

These limitations are 

1) Erosion: may be water erosion or wind erosion denoted by 'e'

2) Climate

3) Water characteristics

4) Due to excess water, drainage problem

5) Soil by (s): low water holding capacity or low plant nutrient content of soil

B) Lands not suitable for Cultivation:

Such lands has also four classes which all are not capable of supporting Cultivation of crops .

These lands are used for growing grasses , forestry and supporting wild life 

Thus lands are together grouped into eight classes by U.S. soil conservation service 

Class1- 

No limitations hence well suited for intensive crop cultivation have permanent irrigation sysytem , well drained level lands with high water holding capacity

Example of class 1 are alluvial soils of indo Ganggetic plains

Class-2 :

Moderate limitations which reduce choice of crops, require moderate conservation practices

Example of class 2 soils are deep red soils and black soils 

Management practices are strip cropping , Contour tillage , rotation involving grasses and legumes 

Class-3 :

Severe limitations requiring special conservation measures, 

Limitations:

Moderately steep slope , high erosion hazard , very slow water permiability , shallow depth and restricted root zone , low water holding capacity, low fertility

Example

Shallow red soils , slightly saline black soils 

Conservation measures require management practices mentioned for class -2 having high proportion of grasses or legumes in crop rotation

Drainage may also be needed

Class -4 :

Very severe limitations on choice of crops 

•Suitable for occasional Cultivation

• Best use for pasture /hay , extensive use of close growing crops

e.g.

Shallow soils , saline soils , alkaline soils

Class- 5:

Limitations are 

1) Interference from stream flow 

2) Short growing season 

3) Stony or Rocky soils 

4) Ponded areas where drainage is not possible

Pastures can be developed on these soils , used for grazing and forestry 

e.g Arid soils , Rocky soils 

Class -6 :

Moderate limitations on use for grazing/forestry

Class-7 :

Severe limitations which restrict their use for grazing , wood land or wildlife

Class -8 :

Extremely rough land , not suitable for any type of crop production, ita use is restricted to recreation, wildlife, aesthetic purpose and watershed protection

e.g. Sandy beaches , river wash 

Conservation Measures for agl.lands are grouped under two heads viz. 

a) Crop management according to the capability of land and moisture

b) Agronomic and Engineering Measures

Factors influencing measures are

1) Soil 

2) Land slope 

3) Rainfall

Measures:

A) Agronomic Measures 

are adopted where slope is less than 2% and erosion Problems are not severe.

These measures help to - 

1) Intercept raindrops and reduce the splash effect

2) To retard and reduce the over land runoff through the use of 

a) Contour Cultivation:

Cultivation of crops along the contours of a slope 

It has following advantages

a) Conserve soil and water 

b) Conserve soil fertility

c) Increase crop yield 

d) Much less power required

e) less wear and tear of implements and less time is required

Disadvantage:

The establishment of contour farming on undulating land is tedious 

b)Mulching:

Mulch is any material applied on the soil surface to check evaporation and improve soil water 

e.g. crop residues , leaves Manures , straw , plastic films 

Effects of Mulching

1) Mulching affects soil water through 

a) Runoff control 

b) Increased infiltration

c) Decreased Evaporation

d) Weed control

2) improves soil nutrients status through 

a) Organic matter addtion 

b) Differential nitrification 

c) Mineral solubility

3) improvez soil structure

4) Affects soil erodibility

5) affects soil salinity

Types of Mulches:

1) soil mulch or dust mulch:

If the soil surface is loosened , it acts as a mulch for reducing Evaporation.It is called soil mulch or dust mulch

2) Stubble mulch : Crop residues like wheat straw or cotton stalks are left on the soil surface as a stubble mulch

3) Straw mulch : straw is used as a mulching material

4) Plastic mulch : Plastic materials like polyethylene, polyvinyl chloride are used as mulching material

5) Vertical mulching:

Subsoiling is probably the most effective method of breaking hardpans to improve root penetration, aeration and water percolation

To prolong the beneficial effect of subsoiling, a method called vertical mulching 

This is mostly practiced in coffee gardens 

C) Dense growing crops:

Provide  maximum cover to soil 

e.g. Cowpea & moong 

d) Strip Cropping: 

It is defined as the process of growing the series of alternate strips of various types of crops laid out so that all tillage and management practices are performed across the slope or on the contour

It controls the runoff erosion and maintains the soil fertility

It is of four types :

1) Contour strip cropping:

Growing of soil exposing and erosion -permitting crops in strips of suitable widths across the slopes on contour , alternating with strip of soil protecting and erosion resisting crops

2) Field strip cropping:

Planting of farm crops in more or less parallel strips across fairly uniform slopes but not on exact contours .

It is useful for soils of regular slope and of high infiltration rates

3) Wind strip Cropping:

Planting of tall growing crops such as jowar , maize etc and low growing crops in alternately arranged straight and long , parallel strips laid out right across the direction of the prevailing wind 

Here wind direction is cared 

Objective is to control wind erosion rather than water erosion

4) Permanent or Temporary Buffer Strip Cropping:

Strips of perennial legumes , grasses or shrubs on a permanent or temporary basis 

Buffer strips are counter strips of grass or other erosion resisting vegetation between or below cultivated strips or fields

* Strip cropping is not adopted in India on a large scale because of the small size holdings

B) Mechanical Measures:

Are adopted to supplement the agronomical practices and when land slope is more than 2%

Objectives:

1) To Increase the time of concentration by intercepting the runoff and thereby providing an opportunity for the infiltration of water

2) to divide a long slope into several short ones so as to reduce the velocity of runoff and thus prevent erosion

a) Basin -Listing :

Making of small interrupted basin along 

the contour

b) Sub - Soiling :

Breaking of harpan by the sub soiler at 30-60 cm depth and 90-180 cm interval 

c) Contour bunding:

Contour bunding is adopted in arid and semi arid areas with high infiltration and permeability and slope of about 6% 

d) Graded bunding / Channel terraces:

  Suitable for lands having slopes from 2-10 % 

e) Broad bed and furrow (BBF) 

Suitable for managing rainwater in black soils where surface drainage during the monsoon period is a problem.

f) Bench terracing :

Usually practiced on slope ranging from 16-33% 

g) Zing terracing: 

Adopted in lands with 3 to 10% slopes .

✍️Agricos

Vaishnavi Nimkar 🌾🌱