Soil Erosion

ON

Submitted to: - Pankaj Jain Submitted By:- Mukesh Verma Program :- BBA-MBA (Int.) Section :- A Reg. no. :- 3020070181

ACKNOWLEDGEMENT

Firstly I would like to thank the God that He has made this World and He gave birth us as a human beings and God has given us a glorious gift i.e. our beautiful world and He made each and everything which we are required to survive in this world. He gave us beautiful plants, animals, air for breath, water for living and many more things which are very essential for the living and one which the most important things without it we can’t do anything on this word i.e. Earth on which live, walk and do all the activities to survive in this world like farming. Farming can’t possible without earth but in real sense our all agriculture is base on thin layer of earth that is known as SOIL which most valuable & essential for the farming because it has a large no of nutrients . But in 21st century this valuable soil is decreasing day-today. India is agriculture based country and most of the population of India is engage in agriculture and the agriculture area has a great contribution in National Income or to development of country. In India there is a large numbers of farmers who are engage in farming and they know that the fertile Soil is very important for their good crops. But due to the Soil Erosion their fertile soil is decreasing day-today. This report will help you to know about the soil, its forming factors, causes of removing soil and how to control this valuable soil & to sustain the lives.

CONTENTS 2

Our Beautiful Word…………………………………..4 •

Glorious Gift of Nature………………………….……….4

Our Earth……………………………………………...5 • • • •

Where we live…………………………………………....5 What is Soil?......................................................................6 Story of Soil……………………………………………...7 Formation………………………………………………...8

The Five Forming Factors............................................9 1. Parent Material 2. Climate 3. Organisims 4. Time

Soil Erosion…………………………………………..11 • • •

What is Soil Erosion?......................................................11 Did you know …………………………………………..12 Effects of Soil Erosion………………………………....14

Types of Soil Erosion………………………………..15 • • • •

Water Erosion…………………………………………...15 Wind Erosion…………………………………………....17 Gravitical Erosion…………………………………….…18 Frozen-Melt Erosion…………………………………….19

Causes of Soil Erosion……………………………….21 • • • •

Climate Factor…………………………………………..22 Soil Feature Factor………………………………….…..23 Geological Factor………………………………………23 Biological Factor………………………………………..25 3

Now Our Glorious Gift………………………………27 How to Control Soil Erosion………………………...30 1. Cover Method…………………………………………30 • Mulching • Cover crops and green manures • Green manures • Mixed cropping and inter-cropping • Early planting • Crop residues • Agroforestry • Minimum cultivation

2. Barrier methods……………………………………….32 • • • •

Man-made terraces Contour ploughing Contour barriers Natural tracces

Methods for sloping land…………………………….34 Solution for Soil Erosion…………….........................35 Conclusion……………………………………………36 Bibliography………………………………………….37

OUR BEAUTYFUL WORLD 4

GLORIOUS GIFT OF NATURE

OUR EARTH 5

WHERE WE LIVE

Soil on which we live and do all those things for survive in this world. Where we do all those activities like:Agriculture, Economic Activities to fulfill our wants.

SOIL 6

What is Soil? SOIL may be defined as a thin layer of earth's crust which serves as a natural medium for growth of plants. 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 the parent 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 some are 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. Soil erosion is a natural process. It becomes a problem when human activity causes it to occur much faster than under natural conditions. Soil covers a major portion of the earth's land surface. It is an important natural resource that either directly or indirectly supports most of the planet's life. Life here depends upon soil for food. Plants are rooted in soil and obtain needed nutrients there. Animals get their nutrients from plants or from other animals that eat plants. Many animals make their homes or are sheltered in the soil. Microbes in the soil cause the breakdown and decay of dead organisms, a process that in turn adds more nutrients to the soil. Soil is a mixture of mineral and organic materials plus air and water. The contents of soil varies in different locations and is constantly changing. There are many different kinds and types of soils. Each has certain characteristics including a specific color and composition. Different kinds of soils support the growth of different types of plants and also determine how well 7

that plant life grows. Soil is formed slowly, but can be easily destroyed. Therefore, soil conservation is important for continued support of life.*

Story of Soil 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 to create 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 in soil 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. 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 alone there are over 50,000 different soils! Specific factors are 8

involved in forming soil and these factors vary worldwide, creating varied soil combinations and soil properties worldwide.

Formation Soil formation, or pedogenesis, is the combined effect of physical, chemical, biological, and anthropogenic processes on soil parent material resulting in the formation of soil horizons. Soil is always changing. The long periods over which change occurs and the multiple influences of change mean that simple soils are rare. While soil can achieve relative stability in properties for extended periods of time, the soil life cycle ultimately ends in soil conditions that leave it vulnerable to erosion. Little of the soil continuum of the earth is older than Tertiary and most no older than Pleistocene.[7] Despite the inevitability of soils retrogression and degradation, most soil cycles are long and productive. How the soil "life" cycle proceeds is influenced by at least five classic soil forming factors: regional climate, biotic potential, topography, parent material, and the passage of time. An example of soil development from bare rock occurs on recent lava flows in warm regions under heavy and very frequent rainfall. In such climates plants become established very quickly on basaltic lava, even though there is very little organic material. The plants are supported by the porous rock becoming filled with nutrient bearing water, for example carrying dissolved bird droppings or guano. The developing plant roots themselves gradually breaks up the porous lava and organic matter soon accumulates but, even before it does, the predominantly porous broken lava in which the plant roots grow can be considered a soil.

The Four Soil Forming Factors 1. Parent material: The primary material from which the soil is formed. Soil parent material could be bedrock, organic material, 9

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 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 soil and enriches the soil. 4. Time: All of the above factors assert themselves over time, often hundreds or thousands of years. Soil profiles continually change from weakly developed to well developed over time.

_____________________________________________________________ *http://en.wikipedia.org/wiki/Soil#Characteristics *http://42explore.com/dirt.htm *http://staffweb.wilkes.edu/brian.oram/soilformingfactors.html

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

SOIL EROSION 11

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 million years, 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 much faster 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 a long distance) deposited. Accelerated soil erosion by water or wind may affect both agricultural areas and the natural 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 soil ends 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 of soil degradation. Other kinds of soil degradationinclude salinisation, nutrient loss, and compaction. Soil erosion is when the soil is blown away by the wind or washed away by the rain. Soil erosion is common in areas with steep slopes, where trees have been cut down, in droughts when crops and other vegetation grows poorly and in rural areas which are 12

overpopulated. Nepal, in the Himalayan Mountains, has severe problems caused by increased population density and steep slopes. Soil erosion can be reduced by building terraces on hillsides, irrigation schemes to overcome droughts, planting more trees to bind the soil together and make wind breaks, and using fertilisers in overpopulated areas to make the soil more fertile. It is very important that the farming techniques used do not damage the structure of the soil, as this makes it easily eroded. Good farming techniques include contour ploughing, crop rotation and keeping the soil rich in humus. An example of poor techniques was the "Dust Bowl" in the mid-western states of the U.S.A. in the 1930's. Farmers exhausted the soil by monoculture and left the soil bare after harvesting. Soil erosion is a problem of the developed world as well as the developing.*

Did you know Annual soil loss in South Africa is estimated at 300 - 400 million tonnes, nearly three tonnes for each hectare of land. Replacing the soil nutrients carried out to sea by our rivers each year, with fertilizer, would cost R1000 million. For every tonne of maize, wheat, sugar or other agricultural crop produced, South Africa loses an average of 20 tonnes of soil. The FAO (Food and Agriculture Organisation, a branch of United Nations) estimates that the global loss of productive land through erosion is 5-7 million ha/year.

More Animal

Overgazing

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More People

More Firefood

Deforestrtion

Bare Soil

Overcultivation

More crops More Hazard

Insects eat crop

Desertification Drought The land provides

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*http://www.scalloway.org.uk/phye6.htm * http://www.bcb.uwc.ac.za/Envfacts/facts/erosion.htm

EFFECTS OF SOIL EROSION 14

The loss of soil by the action of rainfall, run off or wind The consequences of which: Eroded soil may be deposited on other land or in water courses, rivers, lakes, estuaries Worldwide up to 75 billion tonnes of topsoil are eroded every year equating to: . 9 million ha. of productive land lost 80% of worlds agricultural soils are affected by erosion. Thompson (1995) Increasing sea level Agriculture Weather

http://www.ecifm.rdg.ac.uk/erosion.htm

Types of Soil Erosion 15

Water erosion Raindrops can be a major problem for farmers when they strike bare soil. With an impact of up to 30 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 by rainfall 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 common form 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.

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Gullies are larger than rills and cannot be fixed by tillage. Gully erosion is an 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.

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Wind erosion 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 2 800 000 ha susceptible when poor management and unfavourable weather conditions combine. The associated loss in production costs $3 million annually.

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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.

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 requires analysis 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) ability of that material. Factors 19

increasing shear stress include erosion or excavation undermining the foot of a slope, loads of buildings or embankments, and loss of stabilising roots through removal 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 cohesive strength 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 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 repeatedly thaws and freezes. It causes steep cliffs in this region. A particularly mysterious form of 20

frost damage is frost heave, resulting in damaged roads, buildings and 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 and freezing 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, it leaves 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 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 next thawing/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.

http://www.omafra.gov.on.ca/english/engineer/facts/87040.htm#Erosion%20by%20Water http://www.omafra.gov.on.ca/english/engineer/facts/87040.htm#Erosion%20by%20Wind http://en.wikipedia.org/wiki/Soil_erosion 21

www.uni-graz.at/geowww/hmrsc/pdfs/hmrsc4/ZhEA_hm4.PDF

Causes of Soil Erosion Erosion is an incluxive term for the detachment and removal of soil and rock by the action of 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 mass wasting. 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 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: 22

Erosion=f(Erosivity, Erodibility).

Climate factor The major climatic factors which influence runoff and 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 to freeze. 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 on vegetation, 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. 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 process sometimes 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 detached grains. wash is the process in which soil particles are entrained and transported by shallow sheet flows (overland 23

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 the soil. 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 practice, to measure the appropriate values of c 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 the varying 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 24

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 be more runoff, and runoff velocities will be faster. Because of this combination of factors the amount of erosion is not just proportional to the steepness of the slope, but rises rapidly with increasing angle. Mathematically the relationship is: EµS2 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

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velocity of overland flow, and rills 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 soil loss and slope length may be expressed as: EµLb 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 more representative.

Biological factor Vegetation offsets the effects on erosion of the other factorsclmate, topography, and soil 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 low temperatures which cause cracking or frost heaving and needle ice formation; 26

(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; 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, overcultivation 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 nutrientrich 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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NOW OUR GLORIOUS GIFT

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How to control soil erosion

COVER methods These methods all protect the soil from the damaging 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 to cover the soil, also reducing weeds. Sometimes they are grown under fruit trees or taller, slow maturing crops. Sometimes they also produce food or 31

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 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 years in 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 protection from rain splash. Fruit, trees, legume trees for fodder or firewood and alley cropping all help reduce soil erosion. Minimum cultivation Each time the soil is dug or ploughed, it is exposed to erosion. 32

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. Wellbuilt 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 terraces are unlikely to be an appropriate method in countries with no tradition of terrace building. Contour ploughing Whenever possible all land should be ploughed along 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 some examples: old crop stalks and leaves, stones, grass strips, ridges and ditches strengthened by planting with grass or trees. 33

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 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 a natural 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. 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 years each media luna will be covered with vegetation. Later, as the soil continues to improve, crops may be grown in the medias lunas.

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SOLUTIONS FOR SOIL EROSION 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 this may 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 carefully managed 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 for quarries or mines is granted.

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CONCLUSION

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BIBLIOGRAPHY  http://en.wikipedia.org/wiki/Soil#Characteristics  http://42explore.com/dirt.htm  http://staffweb.wilkes.edu/brian.oram/soilformingfactors.h tml  http://www.scalloway.org.uk/phye6.htm  http://www.bcb.uwc.ac.za/Envfacts/facts/erosion.htm http://www.ecifm.rdg.ac.uk/erosion.htm  http://www.omafra.gov.on.ca/english/engineer/facts/87040.htm#Erosion%20by%20Water  http://www.omafra.gov.on.ca/english/engineer/facts/87040.htm#Erosion%20by%20Wind  http://en.wikipedia.org/wiki/Soil_erosion  www.unigraz.at/geowww/hmrsc/pdfs/hmrsc4/ZhEA_hm4.PDF  http://images.google.co.in/images?hl=en&q=Soil+Erosion &btnG=Search+Images&gbv=2 

 BOOK: Soil Erosion: Processes, Predicition,

Measurement, and Control. By Terrence J. Toy, George R. Foster, Kenneth G. Renard Page no. 133-157 and 203-239

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