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Submitted to: - Pankaj Jain

Submitted By:- Mukesh Verma

Program :- BBA-MBA (Int.)Section :- A

Reg. no. :- 3020070181


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OUR BEAUTYFUL WORLD

GLORIUS GIFT OF NATURE


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OUR EARTH

WHERE WE LIVE

Soil on which we live and do all those things for survive in thisworld. Where we do all those activities like:-

Agriculture, Economic Activities to fulfill our wants.

SOIL


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What is Soil?

SOIL may be defined as a thin layer of earth's

crust which serves as a natural medium for growth

ofplants. It is the unconsolidated mineral matter

that has been subjected to, and influenced by,

genetic and environmental factors-- parent

material, climate, organisms and topography all

acting over a period of time. Soil differs from theparent material in the morphological, physical ,

chemical and biological properties. Also, soils

differ among themselves in some or all the

properties, depending on the differences in the

genetic and environmental factors. Thus some soils

are red, some are black; some are deep and some

are shallow; some are coarse textured and someare fine-textured. They serve as a reservoir of

nutrients and water for crops, provide mechanical

anchorage and favourable tilth. The components of

soil are mineral matter, organic matter, water and

air, the proportions of which vary and which

together form a system for plant growth; hence the

need to study the soils in perspective.

Story of Soil
http://www.krishiworld.com/html/plant_crops1.htmlhttp://www.krishiworld.com/html/comm_crop-s1.htmlhttp://www.krishiworld.com/html/plant_crops1.htmlhttp://www.krishiworld.com/html/comm_crop-s1.htmlhttp://www.krishiworld.com/html/plant_crops1.htmlhttp://www.krishiworld.com/html/plant_crops1.html


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Although many of us don't think about the ground

beneath us or the soil that we walk on each day,

the truth is soil is a very important resource.

Processes take place over thousands of years tocreate a small amount of soil material.

Unfortunately the most valuable soil is often used

for building purposes or is unprotected and erodes

away. To protect this vital natural resource and to

sustain the world's growing housing and food

requirements it is important to learn about soil,

how soil forms, and natural reactions that occur insoil to sustain healthy plant growth and purify

water. Soil is important to the livelihood of plants,

animals, and humans. However, soil quality and

quantity can be and is adversely affected by

human activity and misuse of soil.

Certain soils are best used for growing crops that

humans and animals consume, and for building

airports, cities, and roads. Other types of soil have

limitations that prevent them from being built

upon and must be left alone. Often these soils

provide habitats for living creatures both in the

soil and atop the soil. One example of soils that

have use limitations are those that hold lakes,

rivers, streams, and wetlands. Humans don't

normally establish their homes in these places, but

fish and waterfowl find homes here, as do the

wildlife that live around these bodies of water.
http://soil.gsfc.nasa.gov/inch/soiltime.htmhttp://soil.gsfc.nasa.gov/inch/soiltime.htmhttp://soil.gsfc.nasa.gov/inch/soiltime.htmhttp://soil.gsfc.nasa.gov/inch/soiltime.htm


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Natural processes that occur on the surface of

Earth as well as alterations made to earth material

over long periods of time form thousands of

different soil types. In the United States alonethere are over 50,000 different soils! Specific

factors are involved in forming soil and these

factors vary worldwide, creating varied soil

combinations and soil properties worldwide:

The Five Soil Forming Factors

1. Parent material: The primary material from

which the soil is formed. Soil parent material could

be bedrock, organic material, an old soil surface,

or a deposit from water, wind, glaciers, volcanoes,

or material moving down a slope.

2. climate: Weathering forces such as heat, rain,

ice, snow, wind, sunshine, and other environmental

forces, break down parent material and affect how

fast or slow soil formation processes go.

3. Organisms: All plants and animals living in or

on the soil (including micro-organisms and

humans!). The amount of water and nutrients,

plants need affects the way soil forms. The way

humans use soils affects soil formation. Also,

animals living in the soil affect decomposition of

waste materials and how soil materials will be
http://soil.gsfc.nasa.gov/soilform/parmat.htm#Parent%20Materialshttp://soil.gsfc.nasa.gov/soilform/weather.htmhttp://soil.gsfc.nasa.gov/soilform/parmat.htm#Parent%20Materialshttp://soil.gsfc.nasa.gov/soilform/weather.htm


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moved around in the soil profile. On the soil

surface remains of dead plants and animals are

worked by microorganisms and eventually become

organic matter that is incorporated into the soiland enriches the soil.

4. Topography: The location of a soil on a

landscape can affect how the climatic processes

impact it. Soils at the bottom of a hill will get more

water than soils on the slopes, and soils on the

slopes that directly face the sun will be drier than

soils on slopes that do not. Also, mineral

accumulations, plant nutrients, type of vegetation,

vegetation growth, erosion, and water drainage are

dependent on topographic relief.

5. Time: All of the above factors assert themselves

over time, often hundreds or thousands of years.

Soil profiles continually change from weaklydeveloped to well developed over time.

Differences in soil forming factors from one

location to another influence the process of soil

formation


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Image courtesy of the United States Department of

Agriculture, Soil Conservation Service


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What is soil erosion?

Soil is naturally removed by the action of water or

wind: such 'background' (or 'geological') soil

erosion has been occurring for some 450 millionyears, since the first land plants formed the first

soil. Even before this, natural processes moved

loose rock, or regolith, off the Earth's surface, just

as has happened on the planet Mars.

In general, background erosion removes soil at

roughly the same rate as soil is formed. But

'accelerated' soil erosion loss of soil at a muchfaster rate than it is formed is a far more recent

problem. It is always a result of mankind's unwise

actions, such as overgrazing or unsuitable

cultivation practices. These leave the land

unprotected and vulnerable. Then, during times of

erosive rainfall or windstorms, soil may be

detached, transported, and (possibly travelling along distance) deposited.

Accelerated soil erosion by water or wind may

affect both agricultural areas and the natural
http://news.bbc.co.uk/1/hi/world/south_asia/1713001.stmhttp://soilerosion.net/doc/erosion_on_other_planets.htmlhttp://soilerosion.net/doc/water_erosion.htmlhttp://soilerosion.net/doc/wind_erosion.htmlhttp://news.bbc.co.uk/1/hi/world/south_asia/1713001.stmhttp://soilerosion.net/doc/erosion_on_other_planets.htmlhttp://soilerosion.net/doc/water_erosion.htmlhttp://soilerosion.net/doc/wind_erosion.html


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environment, and is one of the most widespread of

today's environmental problems. It has impacts

which are both on-site (at the place where the soil

is detached) and off-site (wherever the eroded soilends up).

More recently still, the use of powerful

agricultural implements has, in some parts of the

world, led to damaging amounts of soil moving

downslope merely under the action of gravity: this

is so-called tillage erosion.

Soil erosion is just one form ofsoil degradation.

Other kinds of soil degradationinclude salinisation,

nutrient loss, and compaction.

Types of Soil Erosion
http://soilerosion.net/doc/extent_of_erosion.htmlhttp://soilerosion.net/doc/on-site.htmlhttp://soilerosion.net/doc/off-site.htmlhttp://soilerosion.net/doc/tillage_erosion.htmlhttp://www.fao.org/landandwater/agll/glasod/glasodmaps.jsphttp://glossary.eea.europa.eu/EEAGlossary/S/soil_salinisationhttp://www.nrw.qld.gov.au/monitoring_guide/impacts/soil_nutrient_loss.htmlhttp://www.extension.umn.edu/distribution/cropsystems/DC3115.htmlhttp://soilerosion.net/doc/extent_of_erosion.htmlhttp://soilerosion.net/doc/on-site.htmlhttp://soilerosion.net/doc/off-site.htmlhttp://soilerosion.net/doc/tillage_erosion.htmlhttp://www.fao.org/landandwater/agll/glasod/glasodmaps.jsphttp://glossary.eea.europa.eu/EEAGlossary/S/soil_salinisationhttp://www.nrw.qld.gov.au/monitoring_guide/impacts/soil_nutrient_loss.htmlhttp://www.extension.umn.edu/distribution/cropsystems/DC3115.html


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Water erosion

Raindrops can be a major problem for farmers

when they strike bare soil. With an impact of up to30 mph, rain washes out seed and splashes soil into

the air. If the fields are on a slope the soil is

splashed downhill which causes deterioration of

soil structure. Soil that has been detached by

raindrops is more easily moved than soil that has

not been detached. Sheet erosion is caused by

raindrops. Other types of erosion caused byrainfall include rill erosion and gullies.

Sheet erosion is defined as the uniform removal of

soil in thin layers from sloping land. This, of

course, is nearly impossible; in reality the loose soil

merely runs off with the rain.

Rill erosion is the most commonform of erosion. Although its

effects can be easily removed by

tillage, it is the most often

overlooked. It occurs when soil

is removed by water from little streamlets that run

through land with poor surface draining. Rills can

often be found in between crop rows.

Gullies are larger than rills and cannot

be fixed by tillage. Gully erosion is an


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advanced stage of rill erosion, just as rills are often

the result of sheet erosion.

Once rills are large enough to

restrict vehicular access they

are referred to as gullies or

gully erosion. Major

concentrations of high-

velocity run-off water in these

larger rills remove vast amounts of soil. This

results in deeply incised gullies occurring along

depressions and drainage lines.

Wind erosion


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Wind erosion is the

movement and

deposition of soil

particles by wind.

Wind erosion occurs when soils bared of

vegetation are exposed to high-velocity wind.

When its velocity overcomes the gravitational and

cohesive forces of the soil particles, wind will move

soil and carry it away in suspension.1 Wind moves

soil particles 0.1-0.5 mm in size in hopping or

bouncing fashion (known as saltation) and those

greater than 0.5 mm by rolling (known as soil

creep). The finest particles (less than 0.1 mm)

detach into suspension. 1 Wind erosion is most

visible during the suspension stage, as dust storms,

or subsequently as deposition along fencelines and

across roads.The process sorts soil particles,

removing the finer material containing the organic

matter, clay and silt through suspension and

leaving the coarser, less fertile material behind. In

the short term this reduces the productive capacity

of soil, as most of the nutrients plants need are

attached to the smaller colloidal soil fraction. Over

a longer period the physical nature of the soil

changes as the subsoil is exposed.1 Wind erosion

also causes damage to public utilities, for example

soil deposition across roads, and reduces crops

through sandblasting.2 It has been estimated that

700 000 ha in Victoria are affected, with another 2


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800 000 ha susceptible when poor management

and unfavourable weather conditions combine.

The associated loss in production costs $3 million

annually.

Wind erosion,

unlike water, cannot

be divided into such

distinct types.

Occurring mostly in

flat, dry areas and

moist sandy soils

along bodies of

water, wind erosion

removes soil and natural vegetation, and causes

dryness and deterioration of soil structure. Surface

texture is the best key to wind erosion hazard

potential. All mucks, sands, and loamy sands can

easily be detached and blown away by the wind,

and thus are rated a severe hazard. Sandy loams

are also vulnerable to wind, but are not as

susceptible to severe wind erosion as the previously

mentioned soils. Regular loams, silt loams, and

clay loams, and clays are not damaged by the

wind, but on wide level plains, there may be a loss

of fine silts, clays, and some organic matter.


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Gravitical erosion

In mass movement of soil - slides,slips, slumps, flows and landslides -

gravity is the principal force acting to

move surface materials such as soil

and rock.1 When natural slope

stability is disrupted, a range of

complex sliding movements may

occur. Detailed classification requiresanalysis beyond the scope of this guide. As a rule of

thumb, rapid movements of soil or rock that

behave separately from the underlying stationary

material and involve one distinct sliding surface

are termed landslides. A slower long-term

deformation having a series of sliding surfaces and

exhibiting viscous movement is termed 'creep'.Such movement is rarely the result of a single

factor, but more often the final act in a series of

processes involving slope, geology, soil type,

vegetation type, water, external loads and lateral

support.mass movement.

Generally mass movement occurs

when the weight (shear stress) of the

surface material on the slope exceeds

the restraining (shear strength)


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ability of that material. Factors increasing shear

stress include erosion or excavation undermining

the foot of a slope, loads of buildings or

embankments, and loss of stabilising roots throughremoval of vegetation. Vegetation removal and

consequent lower water use may increase soil

water levels, causing an increase in pore water

pressure within the soil profile.2 Increased pore

water pressure or greater water absorption may

weaken inter-granular bonds, reducing internal

friction and therefore lessening the cohesivestrength of the soil and ultimately the stability of

the slope.

Frozen-melt erosion

When water freezes, it expands suddenly and with

tremendous force. When water inside a crack in a

rock freezes, its expansive strength may be


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sufficient to crack the rock and to break parts off

it. Frost is tremendously active in snow-covered

mountains, particularly along the snow boundary

where water repeatedlythaws and freezes. It

causes steep cliffs in this

region.

A particularly mysterious

form of frost damage is

frost heave, resulting in

damaged roads, buildingsand cropland. It appears as if the frost heaved

sections of the land upward, by as much as 20cm

and usually in very irregular ways. As can be

expected, frost heave works with the strength of

frost.

Frost heave is not predictable but happens after a

deep frost period, followed by thawing andfreezing again, and a few repeats of this sequence.

In permafrost soils of the arctic, it causes

engineering headaches that have to be met with

special solutions.

Frost heave can be understood as follows: a deep

frost, or permafrost freezes the soil to a certain

depth. When this frost thaws incompletely, itleaves a frozen layer behind. Underneath it, the

soil may still be thawed but in permafrost places,

this frozen bottom is always present. Above it,

melting water collects. A repeated frost now freezes


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it again from the top down, forming a hard layer

on top with water in between the two frozen layers.

As the frost progresses deeper, the entire top layer

is pushed up a few centimetres. The nextthawing/freezing cycle repeats this, ratcheting the

top layer higher and higher, and always with the

same force. Only when the deepest layer is thawed

again, will frost heaving stop.

It is not known how much erosion is caused by

frost heaving, but it can damage soil structure.

Causes of Soil Erosion

Erosion is an incluxive term for the detachment

and removal of soil and rock by the action of


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running water, wind, waves, flowing ice, and mass

movement. on hillslopes in most parts of the world

the dominant processes are action by raindrops,

running water, subsurface water, and masswasting. The activity of waves, ice, or wind may be

regarded as special cases restricted to particular

environment.

Climate and geology are the most important

influences on erosion with soil character and

vegetation being dependent upon them and

interrelated with each other. The web of

relationships between the factors which influence

erosion is extremly complex. Vegegation, for

example, is dependent upon climate, especially

rainfall and temperature, and upon the soil which

is derived from the weathered rock forming the

topography. Vegetation in its turn influences the

soil through the action of roots, take-up of

nutrients, and provision of organic matter, and it

protect the soil from erosion. The importance of

this feedback is most obvious when the vegetation

cover is inadequate to protect the soil, for eroded

soil cannot support a close vegetation cover. The

operation of the factors which influence erosion is

most readily seen in their effect upon the

disposition of storm rainfall. By comparison with

the high runoff from an eroded catchment a well-

vegetated catchment with a permeable soil will


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experience higher infiltration, lower surface

runoff, and less surface erosion.

Erosion is a function of the eroding power of

raindrops, running water, and sliding or flowing

earth masse, and the erodibility of the soil, or:

Erosion=f(Erosivity, Erodibility).

Climate factor

The major climatic factors which influence runoffand erosion are precipitation, temperature, and

wind. Precipitation is by far the most important.

Temperature affects runoff by contributing to

changes in soil moisture between tains, it

determines whether the precipitation will be in the

form of rain or snow, and it changes the absorptive

properties of the soil for sater by causing the soil tofreeze. Ice in the soil, particularly needle ice, can

be very effective in raising part of the surface of

bare soil and thus making it more asily removed

by rnuoff or wind. The wind effect includes the

power to pick up and carry fine soil particles, the

influence it exerts on the angle and impact of

raindrops and, more rarely, its effect onvegetation, especially by wind-throw of trees.

Many reports of soil erosion phenomena have their

value limited by uncertainties in the terminology

used, consequently the key terms are defined here.


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Raindrop erosion is recognized as being

responsible for four effects: (1) disaggregation of

soil aggregates as a result of impact; (2) minor

lateral displacement of soil particles (a processsometimes referred to as creep );(3) splashing of

soil particles into the air (sometimes called

saltation); (4) selection or sorting of soil particles

by raindrop impact which may occur as a result of

two effects-(a) the forcing of fine-grained particles

into soil voids causing the infiltration rate to be

reduced and (b)selective splashing of detachedgrains. wash is the process in which soil particles

are entrained and transported by shallow sheet

flows (overland flow). Rainwash is the combined

effect from raindrops falling into a sheet flow.

Soil feature factor

The soil factor is expressed in the erodibility of thesoil. Erodibility, unlike the determination of

erosivity of rainfall, is difficult to measure and no

universal method of measurement has been

developed. The main reason for this deficiency is

that into two groups: those which are the actual

physical features of the soil; and those which are

the result of human use of the soil.

The resistance of soil to detachment by raindrop

impact depends upon its shear strength, that is its

cohesion (c) and angle of friction. It is difficult, in


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practice, to measure the appropriate values ofc

and for grains at the suface of a soil or soil crust,

partly because of variability in the size, packing,

and shape of particles and partly because of thevarying degrees of wetting and submergence of

grains by water. More success has been achieved

with simplw rotational shear vanes than with most

other methods.

Many attempts have been made to relate the

amount of erosion from a soil to its physical

characterisics. Pinoneer work in this field was

done in North American in the 1930s. Bouyoucos

(1935) suggested that erodibility is related to the

sizes of the particles of the soil in the ratio:

(per cent sand +percent silt)/percent clay

Geological factor

This factor is evident in the steepness and length of

slopes. Nearly all of the experimental work on the

slope effect has assumed that the slopes are

undercultivation. In such conditions raindrop

splash will move material further down steep

slopes than down gentle ones, there is likely to bemore runoff, and runoff velocities will be faster.

Because of this combination of factors the amount

of erosion is not just proportional to the steepness


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of the slope, but rises rapidly with increasing

angle. Mathematically the relationship is: ES2

where E is the erosion, S the slope in

per cent, and a is an exponent.

Values of a derived experimental range

from 1.35 to 2.

The lengh of slope has a similar effect

upon soil loss, because on a long slope there can be

a greater depth and velocity of overland flow, andrills can develop more readily than on short slopes.

Because there is a greater area

of land on long than on short

slope facets of the same width,

it is necessary to distinguish

between total soil loss and soil

loss per unit area. The relationship between soilloss and slope length may be expressed as: ELb

Where E is the soil loss per unit area, L is the

length of slope, and b is an exponent. In a series of

experiments Zingg found that the values of b are

around 0.6 but experiments elsewhere indicated

that a rather higher value is morerepresentative.

Biological factor

Vegetation offsets the effects on erosion of the

other factors-clmate, topography, and soil


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characteristics. The major effects of vegetation fall

into at least seven main categories:

(1) the interception of rainfall by the vegetation

canopy;

(2) the decreasing of velocity of runoff, and hence

the cutting action of water and its capacity to

entrain sediment;

(3) root effects in increasing soil strength,

granulation, and porosity;

(4) biological activityies associated with vegetative

growth and their influence on soil porosity;

(5) the transpiration of water, leading to the

subsequent drying out of the soil;

(6) insulation of the soil against high and lowtemperatures which cause cracking or frost

heaving and needle ice formation;

(7) compaction of underlying soil.The importance

of plants

Plants provide protective cover on the land and

prevent soil erosion for the following reasons:

plants slow down water as it flows over the land

(runoff) and this allows much of the rain to soak

into the ground;


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Plant roots hold the soil in position and prevent it

from being washed away;

Plants break the impact of a raindrop before it hits

the soil, thus reducing its ability to erode;Plants in wetlands and on the banks of rivers are

of particular importance as they slow down the

flow of the water and their roots bind the soil, thus

preventing erosion.

The loss of protective vegetation through

deforestation, over-grazing, ploughing, and fire

makes soil vulnerable to being swept away by wind

and water. In addition, over-cultivation and

compaction cause the soil to lose its structure and

cohesion and it becomes more easily eroded.

Erosion will remove the top-soil first. Once this

nutrient-rich layer of soil is gone, few plants will

grow in the soil again. Without soil and plants the

land becomes desert-like and unable to support life

- this process is called desertification. It is very

difficult and often impossible to restore desertified

land.


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WE ARE RESPONSIBLE FOR THIS


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Oh!


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How to control soil erosion


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COVER methods

These methods all protect the soil from thedamaging effects of rain-drop impact. Most will

also improve soil fertility.

Mulching

Bare soil between growing plants is covered with

a layer of organic matter such as straw, grasses,

leaves and rice husks - anything readily available.

Mulching also keeps the soil moist, reduces

weeding, keeps the soil cool and adds organic

matter. If termites are a problem, keep the mulch

away from the stems of crops.

Cover crops and green manures

Cover crops are a kind of living mulch. They are

plants - usually legumes - which are grown tocover the soil, also reducing weeds. Sometimes

they are grown under fruit trees or taller, slow

maturing crops. Sometimes they also produce

food or fodder. Cowpeas, for example may be

used both as a cover crop and a food crop.

Green manures - also usually legumes - are

planted specially to improve soil fertility by

returning fresh leafy material to the soil. They

may be plants that are grown for 1-2 months

between harvesting one crop and planting the


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next. The leaves may be cut and left on the

surface of the soil as a mulch or the whole plant

dug into the soil. Green manures may also be

trees or hedges which may grow for many yearsin a cropping field from which green leaves are

regularly cut for use as mulch (alley cropping).

Mixed cropping and inter-cropping

By growing a variety of crops - perhaps mixed

together, in alternate rows, or sown at different

times - the soil is better protected from rain

splash.

Early planting

The period at the beginning of the rainy season

when the soil is prepared for planting, is when the

damage from rain splash is often worst. Sowing

early will make the period when the soil is bare,

as short as possible.

Crop residues

After harvest, unless the next crop is to be

immediately replanted, it is a good idea to leave

the stalks, stems and leaves of the crop just

harvested, lying on the soil. They will give some

cover protection until the next crop develops.

Agroforestry

Planting trees among agricultural crops helps to

protect the soil from erosion, particularly after

crops are harvested. The trees will give some


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protection from rain splash. Fruit, trees, legume

trees for fodder or firewood and alley cropping

all help reduce soil erosion.

Minimum cultivationEach time the soil is dug or ploughed, it is

exposed to erosion. In some soils it may be

possible to sow crops without ploughing or

digging, ideally among the crop residue from the

previous crop. This is most likely to be possible in

a loose soil with plenty of organic matter.

2. BARRIER methods

Barrier methods all slow the flow of water down

a slope. This greatly reduces the amount of soil

which run-off water can carry away and

conserves water. Any kind of barrier should

work. To be effective any barrier must follow the

contour lines.

Man-made terraces

In some countries terracing has been successfully

practised for centuries - the Philippines, Peru and

Nepal, for example. Well-built terraces are one of

the most effective methods of controlling soil

erosion, especially on steep slopes. However,terraces require skill and very hard work to

build. Each terrace is levelled - first by levelling

the sub-soil, then the top soil - and firm side

supports are built, often of rock. Man-made


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terraces are unlikely to be an appropriate method

in countries with no tradition of terrace building.

Contour ploughing

Whenever possible all land should be ploughedalong the contour line - never up and down, since

this simply encourages erosion. In some cultures

this may be very difficult due to the pattern of

land inheritance. For example the Luo people in

Western Kenya inherit land in long strips

running down to the river valleys, making

contour ploughing extremely difficult. Soil

conservation programmes may need to consider

land redistribution schemes, or neighbouring

farmers will have to work together.

Contour barriers

Almost any available material can be used to

build barriers along the contours. Here are someexamples: old crop stalks and leaves, stones,

grass strips, ridges and ditches strengthened by

planting with grass or trees.

Natural terraces

David Stockley encourages the use of grass strips.

He writes...

Why do so much hard work (building terraces)

when nature can do it for less? Let us make use of

natural erosion. We planted grass along the

contour lines. We used fibrous grasses with a


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dense root system such as Napier grass,

Guatemala grass and Guinea grass. The strips of

land in between were cultivated. As the soil is

cultivated, nature moves the soil to form anatural terrace. The rainwater passes through

the grass strip, depositing any soil carried behind

the grass. In our experience in Bangladesh and

Brazil, rains formed natural terraces within five

years. Once well established, the grass barrier

can be planted with banana, pineapple, coffee,

fruit or firewood trees.

Vetiver grass has been very effective in grass

strips. It does not spread onto cultivated soil, it

produces sterile seeds, has few pest problems and

can survive in a wide range of climates.

For more information about Vetiver grass, write

to:Vetiver Information Network, World Bank,1818

High Street NW,

Washington DC 20433, USA

Medias lunas

This is a helpful system for reclaiming badly

eroded land which has been used successfully in

Bolivia.Medias lunas or crescent shaped

depressions are built on sloping land. The

crescent shapes are built at the end of the rainy

season so the ridges made can be compacted well.


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The crescent collects the rainwater and soil. Trees

- usually legumes - are planted when the next

rainy season begins and protected by thorn

branches from grazing animals. After 3 or 4 yearseach media luna will be covered with vegetation.

Later, as the soil continues to improve, crops may

be grown in the medias lunas.

SOLUTIONS FOR SOIL EROSION


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1. to prevent erosion of bare soil, it is important to

maintain a vegetation cover, especially in the most

vulnerable areas e.g. those with steep slopes, a dry

season or periods of very heavy rainfall. To do thismay mean only partially harvesting forests (e.g.

alternate trees) and using seasonally dry or wet

areas for pastoral rather than arable agriculture.

2. where intensive cultivation takes place, farmers

should use a crop rotation in order to prevent the

soil becoming exhausted.

Where soils are ploughed in vulnerable areas,

contour ploughing (i.e. round the hillside rather

than down the hillside) should be used.

Careful management of irrigation, to prevent the

application of too much or too little water, should

help reduce the problem of salination.

3. livestock grazing rates must be carefullymanaged to prevent overgrazing.

4. perhaps we must attempt to restrict highway

construction and urbanisation to areas of lower

agricultural potential. With extractive industries, a

pledge must be secured to restore the land to its

former condition before planning permission forquarries or mines is granted.


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