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S.ARUN KUMAR(ASISTANT DIRECTOR)

SOILThe top layer of earth’s surface that is

capable of sustaining life.Is a three dimensional natural body occurring

on the surface of earth that is the medium for plant growth and whose characteristics have resulted from the forces of climate and living organisms acting upon parent material as modified by relief over a period of time.

It is the deterioration of soil by the physical movement of soil particles away from the original site. Water, wind, moving ice, sea waves and the use of implements by human beings etc, are the agents of erosion.(Biotic & abiotic causes)

SOIL EROSION

INDECATORS

• Mounds of relic soils around plants and under pebbles.

IT RESULT IN THE LOSS OF FERTILE TOP SOIL THAT IS SUPPORTING CULTIVATION LOSS OF PLANT NUTRIENTS MAKING LAND UNSUITABLE FOR CULTIVATION BY THE FORMATION OF RAVINES AND GULLIES SOIL ENTERING THE WATER COURSE REDUCES WATER QUALITY,REDUCES THE EFFICIENCY OF DRAINAGE SYSTEMS AND STORAGE CAPACITY OF LAKES AND RESERVOIRS. SOIL IN WATER IS A POLLUTANT AND IN THAT WAY INHIBIT FISH SPAWNING AND ENTRY OF LIGHT INTO WATER THAT IS NECESSARY TO SUSTAIN LIFE IN WATER THE FERTILIZERS/CHEMICALS IN SOIL MAY AFFECT

QUALITY OF WATER FOR DRINKING. CAUSE DAMAGES TO ROADS,RAILS AND WATER TRANSPORT

LOSSES DUE TO EROSION

Others2.71 m ha

Degraded forests24.90 m ha

Water logged3.20 m ha

Salt affected6.32 m ha

Ravines2.68 m ha

Wind erosion10.46 m ha

Water erosion57.16 m ha

Status of land degradation in India (Total Area: 329 m ha)

Source: MOA, 1994

Rain drops falling on earth surface from a height dislodge the fine soil particles from the soil mass. This detached soil particles are carried away in suspension along with overland flow. The flowing water over the land surface also can dislodge large number of soil particles of varying size and ultimately get transported to streams.

Movement of particles

by various agents

(TRANSPORTATION)

PROCESS OF SOIL EROSION

Loosening & dislodging of Particles

DETACHMENT/EROSION

Deposition of the transported particles(SEDEMENTATION)

INDESRIMINATE CUTTING DOWN OF TREES

OVER GRAZING OF VEGETATIVE COVER

FOREST FIRES

REMOVAL OF PLANT NUTRIENTS AND ORGANIC MATTER BY INJUDICIOUS CROPPING PATTERN

CULTIVATION ALONG SLOPES

FAULTY METHODS OF IRRIGATION

GROWING CROPS THAT ACCELERATE EROSION

CAUSES OF SOIL EROSION

TYPES OF EROSION

NATURAL/GEOLOGIC ACCELERATEDErosion of soil in its

natural stateRate of erosion is low

and generally invisible.Soil forming process.There is equilibrium

between soil formation and soil loss.

It happens under biotic and abiotic pressure.

Rate of erosion is high and is visible

Soil degrading processThe equilibrium between

soil formation and soil loss is broken and loss is higher than formation

DIFFERENT FORMS OF WATER EROSION

Loss of soil due to water movement is called water erosion. Excess rainfall generating run off causes water erosion and is increased by the sloping lands.

Rain drop erosion/Splash erosionSheet erosionRill erosion

Gully erosionStream bank erosion

Sea coast/shore erosionLand slide/land slipRavine formation

Rain drop erosion/Splash erosion

• It is the first step in the water erosion process. Splashing/detachment of soil particles occurring by the impact of falling raindrops is called splash erosion. Soil granules are loosened and beaten into pieces. The falling drops at a speed of 9 m/sec can create force of 14 times its weight. By this action the soil becomes a flowing mud. It can splash soil particles to about 60 cm ht and 150 cm away.

• Except in slopping lands it cannot make impact because soil particles

only to very small distances.

SHEET EROSION • The removal of a more or less uniform thin layer or sheet of soil by running water from sloping land is called sheet erosion. The splashed soil seal the soil pores and prevent infiltration and also cause sheet erosion

SHEET EROSION

RILL EROSION

• It is an advanced form of sheet erosion which occurs due to concentration of flowing water. As a result of water washing down the slope small finger like rills begin to develop on land surface. If not cultivated these rills may increase in number size and shape.

RILL EROSION

Gully erosion

RAVINE FORMATION

RAVINE FORMATION

• Ravine is a parallel set of deep and narrow gullies with abrupt sides. They are formed from un attended rills. It is usually associated with river systems.

Causes of ravine formation

• Abrupt changes in elevation between river bed and adjoining land

• Deep and porous soil strata with high erodibility

• Poor vegetative cover• Backflow of water during recession period

STREAM BANK EROSION

• Scouring of soil material from stream

bed and cutting of stream bank by the

force of flowing water. Stream erosion

happens at lower end of water

channels where as gully erosion is

towards upper portion of channels.

SEA COAST/SHORE EROSION

• Tidal waves of the sea and rough and roaring waves dash on the coast every time swallowing bits of land. High velocity winds may intensify the hazards of this erosion

LAND SLIDE /LAND SLIP

• It is the downward and outward movement of soil forming material composed of natural rocks, artificial fills or combination of these materials.

• Land slip-Smaller mass moving all on a sudden.

• Land slide-bigger mass moving slowly moving through initiating as slips

Causes

• GEOLOGIC-weak geology, lack of vegetative cover

• HYDROLOGIC-Water seeping and over saturation

• SEISMIC-Earth quakes

Topography

Length of slope Degree of slope

Slope = Vertical /Horizontal

= tan x

Degree & length of slope

• Steep slope-Velocity increase, depression storage

• Slope increase four times velocity doubles and erosive power increase four times

• Quantity 32 times size -64 times• Length of slope increase also soil erosion

increase

Relative proportion of sand silt and

clay(particle size distribution)-texture• Clay - < 0.002 mm dia

• Silt - 0.002 - 0.05 mm dia

• Sand - 0.05 - 2 mm dia

• >2 mm- gravel

Effect of texture on erosion

Coarse texture• More sand• Light soil• Less erosion• Easily detachable but

difficult to transport

Fine texture• More clay and silt• Heavy soil• More erosion• Silt is easily detachable and

transportable• Clay not easily dispersed

but low infiltration and hence more run off and erosion

Soil structure

• Arrangement/grouping of soil particles

• Granular-more infiltration and less runoff.

• Compact soil-less infiltration and more runoff

SOIL STRUCTURE

SOIL ORGANIC MATTER• Plant and animal residues in various stages

of decomposition• Provide ground cover, sponge,less

evaporation• Increase permeability & water holding

capacity and reduce erosion• Life of soil, Improve structure• Sandy soil-2%• Clay and silt-3%

SOIL PERMEABILITY

• Ability of soil to allow air and water to move through soil.

• High permeable-less erosion and less run off

EROSIVITY

potential ability of rain

to cause erosion for a

given soil condition

ERODIBILITY

Susceptibility of soil to erosion and it depends on the physico-chemical characteristics of the soil & land and crop management factors.

Agronomic Vs Mechanical• Slow establishment• Long life• Low cost• Protective• Remunerative• Productive• Self multiplicating• Soil forming• Less skills• Conserve bio diversity• Eco friendly

• Fast result• Less life• High cost

Biologic and agronomic• Crops or Vegetation• Agronomic practice• Required even in areas where mechanical

measures are adopted for uniform infiltration and moisture distribution

TIMELY SOWING/CANOPY MANIPULATION

• Maximum erosion when the soil is bare without any crop cover.

• Establish the crop as early as possible.

Closer spacings.

Maize June 25 July 1 July 7

Canopy(july 30)

48% 20% 15%

Splash produced

14.5 g 18.4g 20.5g

yield Max Min

CONTOUR FARMING

Contour farming

CONTOUR FARMING

• Ploughing,seeding,planting,interculture in contours

• Easy effective and low cost• Forms ridge and furrows• Most effective in slopes upto 2- 6% slope• Consrve moisture,reduce erosion increase

production

Inter Cropping

• Growing two or more crops simultaneously in the same field following specific row or lne arrangement.

• Effective land use,resource use.

Inter Croppingsystem Yield(q/ha) Inter crop yield

Maize 28.6Maize+pigeonpea 28.2 6.2Sorghum 34.4Sorghum+pegion pea

33.5 5.5

Sorghum 33.5

Sorghum+greengram 30.8 7.3

POST-1ST YEAR

POST-2ND YEAR

INCREASING CROPPING INTENSITY

Strip cropping

Strip cropping• Alternate rows of erosion permitting and

resisting crop.

• Planted on contour for water erosion control.

• Against prevailing wind direction for wind erosion control.

• Usually a strip of cereal with pulse is alternated.

MIXED CROPPING

Rubber + Coffee + Cardamom

çÕøáÕcÞÉÈ¢Root distribution

MIXED CROPPING

• Small holding does not permit strip crop• One main crop and one subsidiary crop• Provide good land cover• Different root zones• Ensure at least one crop in adverse climatic

conditions.

Conservation tillage

• Tillage is the mechanical manipulation of the soil to create necessary soil conditions congenial for plant growth.

• Conservation tillage –minimum disturbance to top soil.

• Zero tillage, minimum tillage, mulch tillage• 30% of crop residue cover is maintained.

Conservation tillage

• Conservation tillage is any system that reduces the number of tillage operations maintains residue cover on the soil surface, and reduces the losses of soil and water relative to conventional tillage. It is a set of innovation technologies including no-till and various reduced or minimum tillage systems such as mulch tillage, strip tillage, and ridge tillage. Reduced or minimum tillage includes any system in which a soil is disturbed less than in conventional tillage but more than in no-till.

Conservation tillageNo-till and reduced-tillage farming leaves old crop residue on the ground instead of plowing it into soil. This covers the soil, keeping it in place. Here, corn grows up out of a “cover crop.”

Figure 8.16f

Reduces erosion

Saves fuel

Cuts costs

Holds more soil water

Reduces soil compaction

Allows several crops per season

Does not reduce crop yields

Reduces CO2

release from soil

Can increase herbicide use for some crops

Leaves stalks that can harbor crop pests and fungal diseases and increase pesticide use

Requires investment in expensive equipment

DisadvantagesAdvantages

Trade-Offs

Conservation Tillage

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Mulching

• Plant residues or other materials over soil surface.

»ADVANTAGES

Mulching

Properties of plants to be selected as barriers

• Erect,stiff uniform,dense permanent hedge• Perennial• Not to Spread as weed• Repel rodents• Deep penetrating roots• Sprout new tillers• Not compete with crop• Farmer friendly• Bio mass to be economic value

Cover crops

Calopo

S.hamata

Stylosanthes guinenesis

Siratro

Puero

Centro

Subabul

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MECHANICAL/Engineering measures

ConceptIntercept long slope into shorter ones.

Does not allow to reach critical velocity.

Reduce/alter degree of slope.

Increase the time of concentration/opportunity time.

LAND LEVELLING/GRADING

LAND LEVELLING/GRADING

• Reshaping the land to a planned grade.• Uneven- No uniformity in irrigation

waterappliction,fertilizer distribution etc.• It enhances irrigation water use efficiency• Low r.f areas reduce run off & max infiltration

LAND LEVELLING/GRADING

• Criteria for land levellig– Soil (depth,texture,infiltration)– Topography (slope)– Cropping pattern(kind of crop,irrigation,returns)– Rainfall– Desire of farmers.

Bunding

• It is an embankment of suitable cross section constructed across the slope to break the slope length. These are the best for ground water recharge.– Contour bunding.– Graded bunding.

Contour bunding

Contour bunding

• Along the approximate contour• Suitable from 2-6% slope,< 800 mm r.f,and

relatively permeable soils.• Is adopted where leveling is impossible for

cost

STONE PITCHED CONTOUR BUND (PUERTORICCAN TYPE CONTOUR

TERRACE WALL)

Top width including pitching: 45 to 50 cm

Thickness of pitching: 15 to 22 cm

Side slope Uphill side of earth

fully: 1.5:1 Downhill side: 1:5 to

1:3 Foundation: 15 to 20

cm

Graded bunding

6-10 % slope Or Clay soil Or rainfall more than 800mm

Safely dispose run off Drainage channel

Merits & Demerits Page 16 ofyr text

Bench terracing

Step like fields by half cutting and half filling 6-33%slope. Or up to 50% In lower slopes for uniform water impounding

LAY-OUT OF BENCH TERRACE

Types of bench terraces

Suitability

Type Slope Soil type Rain fall,mm

Level 8-50 % Medium to deep

<2500-3000

Inward sloping

8-50 % Medium to deep

<2500-3000

Outward sloping

8-50 % Shallow <1200

Puertoricantype

8-50 % Shallow to deep

<1500

Puertorican Type Terrace/California type• Soil is not disturbed for making a terrace in

a single stroke or time• A hedge of suitable grass is planted in a

single or double row on contour at pre-determined spacing.

• The interspace between the two hedge lines of grass planted is cultivated and tilled to take crops.

• The tilled soil slowly moves towards the vegetative hedge and gets deposited against this barrier.

• The process continues for 3 to 4 years till it becomes level .

• Guatemala (Tripsacum laxum) and Hybrid Napier have been found effective for this purpose in the Nilgiris.

• This is much cheaper and does not disturb the top soil.

Conservation bench terracing

Strip terraces

• With lesser terrace width of 1-1.5 m• Design

– Maximum depth of cut (D)– Maximum admissible cut for given slope– Width of terrace.

1.Terrace spacing

2.Terrace gradient

3.Terrace cross section

NON ARABLE LAND CONSERVATION

MEASURES

Diversion drain

Contour trenching

– Break slope length– Reduce erosive velocity– Reduce run off– Retention of water

Contour trenching

CCT SCT

Crib structures

Contour Watling

DRAINAGE LINE TRTEATMENT

Check dams

Functions of check dam

Reduce the channel gradient

Reduce velocity of flow and silt carrying capacity

Percolation & ground water recharge

Promote vegetation growth in channels.

Components of check dam

Spill way to carry the flowAnchoring to side and bottomApron that absorb impact of falling water

Check dams

Temporary

Semi permanent

Permanent

Brush wood dams

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BRUSH WOOD

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Semi permanent

Permanent structures

• Where other inadequate or impractical

• Volume of peak run off is very high

• Sites where frequent maintenance not

possible

• High degree of risk for life/property

Permanent structures, only if

• Help in stabilizing gully and store water

• Adequate to handle Qp

• To be constructed with permanent

material

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Gabion retaining wall

Wind erosion

Wind erosion, also known as eolian erosion, is a dynamic process by which soil particles are detached and displaced by the erosive forces of the wind. Wind erosion occurs when the force of wind exceeds the threshold level of soil’s resistance to erosion.

Causes of wind erosion

• crushed or broken soil surface crusts during windy periods;

• a reduction in the plant cover, biological crusts, and litter, resulting in bare soil;

• a decrease in the amount of organic matter in the soil, causing decreased aggregate stability;

• long, unsheltered, smooth soil surfacesDRY soil conditions-Arids & semi arids

EFFECTS OF WIND EROSION

• REMOVAL OF TOP SOIL• SCALDING ON SOIL SURFACE• ROOT EXPOSURE• SOIL TEXTURAL CHANGES ATTRITION AND

WINNOWING• EXTENSION OF DESERTS• HIGH DUST CONCENTRATION IN ATMOSPHERE

CAUSING HEALTH HAZARDS• DAMAGE TO ROAD, RAIL, BUILDING• SAND DEPOSITS

Wind erosion control

Shelter belt

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1 S¬ s\Ãv \nÀ½n-¡m³ þ 4000 enäÀ

1 enäÀ Milk \nÀ½n-¡m³ þ 900 enäÀ

• The water storage capacity of a particular region remains the same

• The consumption increases

with increase in population

corresponding to changes in life style

RAIN WATER HARVESTING

• Kerala state is receiving 80-90 % of rain fall in a period of 5-6 months and for the rest 6-7 months it is under water insecurity. The fun about Kerala is, 8500 million cubic metre water is excess in monsoon and 7200 million cubic metre deficit in summer. This demands a very meticulous planning for rain water harvesting in the state

The land of 44 rivers is only a fallacy as the total amount of water that all the rivers contain together is less than 2/3rd of Godavari. We have no major rivers and only 4 medium and 40 minor rivers. The largest river is Periyar with a length of 240 km. Kerala is having only < 2 % area under irrigation.

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Physiographically it is demarcated as 48% high land, 42 % mid land and 12% low land. Due to these features of topography the water gets very little time to infiltrate into the soil and the entire rain fall takes very short time to reach the sea. Due to this reason only 6-12% rain is recharged in to the ground in Kerala. With this, the state has to support a population density of 819/km2.

Rainfall availability

• Reeipt-400 million hectare meter –69 million surface water–45 million ground water–This 114 million is 29%–The rest 71% goes to the sea or get evaporated

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• Stress 1700 m3• Water scarce 1000 m3

1955 5300 M3

1990 2200 M3

2005 2000 M3

2025 1465

2050 1235

Sl No. District /Assessment Unit Categorisation for future ground water development (Safe/ Semi-Critical/Critical/Over-exploited)

1 Kollengode Critical

2 Nenmara Safe

3 Thrittala Critical

4 Ottapalam Safe

5 Alathur Safe

6 Pattambi Safe

7 Palakkad Critical

8 Attappadi Semi-critical

9 Kuzhalmannam Safe

10 Mannarkkad Safe

11 Chittur Over exploited

12 Sreekrishnapuram Semi-critical

WATER CYCLE

Water harvesting

• Is the collection, storage and conservation of rainfall for its productive use in irrigation, domestic and industrial uses.

• Is the technique of collection and storage of rain water that runs off a natural or manmade catchment such as watersheds rooftops, compounds, rocky surfaces or hill slopes

Water harvesting techniques

• 1.In situ - where rain fall is received

• 2.Surface water harvesting

• 3. Roof top

2.Surface water harvestingDug outsFlt areas

Embankment typeHilly areas

Dams

RWHS

• Catchment• Gutter• Drain pipes• First flush• Filter unit• Storage tank• Collection sump and

pump unit

Underground cistern

Just like an underground tank but with more storageArid regions for reducing evaporation loss.

Artificial RechargeArtificial Recharge : Augmentation of Ground water reservoir at a rate exceeding that under natural condition

ARTIFICIAL RECHARGE BY SUBSURFACE METHODS

Pond/ tank with shaftRecharge pitRecharge trench Recharge well Injection wellSub surface dams

Dug well recharge Dried up dug wells/ wells in

which water levels have declined can be recharged

Source of recharge can be rain water from storm/tank/canal/

Roof top Recharge water should be passed

through desilting chamber, after desilting the recharge water is taken to bottom of well/ below the water level.

Periodic chlorination.

Dug well recharge

Abandoned Quarries/ Mine pits

Recharge shaft/ Injectionwells

Efficient and cost effective structures

Back filled with inverted filter

Suited for deep water levels (upto 15m)

Silt water can be used

HOW much water do I use ???

Use Litres/person

Drinking 3

Cooking 4

Bathing 20

Flushing 40

Washing-clothes 25

Washing Utensils 20

Gardening 23

Total 135

Consumption range 50 Ltrs/300 ltrs per person per day

A dripping tap could waste as much as 90 litres a week.

Brushing your teeth with the tap running wastes almost 9 litres a minute. Rinse out from a tumbler instead.

Cool water kept in the fridge means you won't have to run the tap for ages to get a cold drink.

Don't use your washing machine until you've got a full load. The average wash needs about 95 liters. A full load uses less water than 2 half loads.

Every time you boil an egg save the cooled water for your houseplants. They'll benefit from the nutrients released from the shell.

Fit a water saving device in your cistern and save up to three litres a flush.

Grow your grass a little longer. It will stay greener than a close mown lawn and need less watering

DRIPS

And human dwelling conditions could not get worse