SOIL EROSION AND ITS CONTROL FOR MAINTAINING SOIL HEALTH

Rashmi Ranjan BarikPROGRAMME OFFICER-NRM, OPELIP, ODISHA

Introduction to Soil Erosion

Definition : Soil erosion is the detachment, transport & deposition of soil

particle on land surface - termed as loss of soil. Measured as mass /unit area - tonne/ha or Kg/sq.mSoil loss is of interest primarily On -site effect of erosion such as loss of crop productivity Off site effect of erosion are siltation in ditches, streams , reservoirs Sediment generated by erosion processes are prime carrier of agricultural chemicals that pollutes stream or lakes

Soil Erosion ProblemSoil is the most precious gift of nature –Prime

resource -for food, fodder etc. -Soil mismanaged -less productivity.

In India, more than 100 million hectares -soil degraded eroded unproductive

About 17 tones/ha soil detached annually->20% of this is transported by river to sea -10% deposited in reservoir results 1 to 2% loss off storage capacity.

Soil erosion deteriorates soil quality & reduces productivity of natural, agricultural & forest ecosystem

Soil erosion deteriorates quality of water Increased sedimentation causes reduction of

carrying capacity of water bodies

Factors Affecting Erosion

Human Causes

Natural Causes

Striking Factors

Degenerating Forces

Factors Affecting Erosion

Erosion is directly proportional to square root of length of slope

Mechanics of ErosionBegins with raindrops striking bare soil dislodging

particles Intense rains seal surface When rainfall exceeds infiltration water is stored in

small depressions Once depressions are filled, runoff beginsInitially water flows in a discontinuous sheet Eventually it concentrates into small channels or rills The runoff now has energy to break off particles and

cut deeper The amount of erosion caused by sheet and rill

erosion increases with slope and distance Rills may eventually form gullies

Soil Erosion ParametersSoil erosion – function of:

Erosivity – ability to erode : depends on rainfall Erodibility – Resistance offered to restrict

erosion (property of soil)Topography – property of land Management – contributed by man

Erodibility: Detachability & transportability Topography: Slope, length, relation to other land

Management: Land use & crop management

Types of Soil ErosionGeological erosion, Natural erosion &

Erosion from activities of human & animalsGeological erosion: -Soil forming and

distribution-Long time process Human and animal: Tillage, removal of

plants and Tillage, removal of plants and other vegetation- accelerated erosion

Stream bank erosion Landslide, Volcanic eruption, flooding Water and wind: major factors of soil

erosion

Soil Erosion Processes

Types of surface erosion

Splash Erosion Sheet Erosion Rill Erosion

Gully Erosion Stream bank Erosion

Types of erosion

Principle of Soil and Moisture Conservation

Ridge to valley treatmentMaximum possible rain water should be

conserved where it fallsAdequate vegetal cover during rainy seasonStorage/ disposal of excess water with safe

velocityChecks/ barriers along the contour to control soil

erosion & ground water rechargeIntegration of biological and mechanical

measures

Soil Conservation

Agronomic Measures

Agronomic Measures

Contour cultivation

Vegetative Barrier

For Sloppy Land For Gully Treatment

Strip cropping

Grass waterway

To allow water to flowIn non-erosive velocityand helps in safe diposalof excess water

Aforestation

Cover Cropping

Mulching

Sugarcane trash mulching

Mulching in mango

Mulching in maize

Conservation Ditches

Agri-horti System ( Mango + G.Nut)

Agri-horti System

Agri-silviculture(A.mangium + sesame)

Silvi - Pastoral system(A.mangium + guinea grass)

Horti-Pastoral System (Banana + Grass)

Horti - Pastoral system

Horti-silvi-pastoral system (Guava + sissoo + stylo)

Important principles for planning engineering measures

Intercepting the rain before it reaches ground surface, dissipate the kinetic energy to reduce detachment of soil particle.

Increasing time of concentration of run off and there by allowing more water to be absorbed and held by soil.

Reduce the run off volume and run off velocity

Protection against damage due to excess run off

Trapping silt particle during its flow path.

InterventionsVegetative cover prevent rain drop to strike ground

surface directly as well reduce its energy.Intercepting long slope into several short ones so as to

restrict the run off velocity with in critical limit.Bunding breaks the slope length, terracing breaks the

degree of slope which increase the time of concentration.

Trenches, check dams, earthen cross bunds, gabion structure, etc. store part of run off there by reducing run off volume and velocity and protect against the damage caused due to excess run off and facilitate GW recharge.

Gully control measures are constructed especially to prevent further increase in gully size (both horizontally and vertically) and to stabilize it to allow vegetation to grow.

Finally utilization of excess water through check dams, diversion weirs, ponds, WHSs, wells for crop production.

Distinct Features Purpose Technological options for development

Situated above Berna land having 8% -25% slope, unlevelled. Soil depth is up to 0.30 m and rain fed cereals, pulses and oilseeds along with rainy vegetables are usually cultivated. Soil erosion and nutrient loss possessions problems.

Safe disposal of run-off water. Breaking the length of slope. Retain a part of run-off. Make the land suitable for tree plantation. Gully stabilization

Option in varying slope

Diversion drain/ Grass water way

Terracing (Level/Inward/Outward)

Continuous contour canal Trenching (CCT/ ST/WAT)

Contour Bunding/ Graded Bunding / Stone Bunding

Percolation Tank

Gully control works (Semi Permanent) Gully Control works (Permanent)

Sunken Gully Pit

Treatment options for different types of lands- Aat land (Up land)

Treatment option in varying slope

Grass waterways

Terracing

Grassed Waterways Diversion DrainContinuous contour canal

Continuous Contour Trenches

Staggered Trench

Water Absorption Trench (WAT)

Slope

Contour Bunding

Contour Stone Bunding

Percolation Tank in upper reach

Sunken Gully Pit

Permanent GC Structures

Semi permanent Gully Control Structure

Distinct features Purpose Technological options for development

Situated above Bahal (low land) with mild slopeof 2% to 8% Under levelled and irrigation situation two crops are assured Paddy with short & medium duration are usually cultivated Erosion takes place due to over flow of runoff water from near by areas

To break the slope length Conserve max. water for crop production. Drainage development. Silt detention.

Field Bunding with outlets. Dev. of Drainage CourseDiversion Weir / Retention Weir.Check dams (Masonry/ Gabion /Low Cost Multiple Arch Type CD)Water Harvesting Structure(WHS) Run-off Management Structure

Treatment options for different types of lands- Berna (medium land)

Field Bunding

Development of drainage course

Diversion Weir

Retention weir/ Wall

Retention Weir Retention Wall

Masonry check dam

Gabion Structure

Masonry Multiple Arch Type Check Dam

Water Harvesting Structure

Run off management Structure

Slope

Contour bunding

Distinct features Technological options for development

* Developed from stream bed where water flows regularly. Jholla land comes under this category.

* Due to retention nature of soil moisture and continuous flow, two crops of paddy are usually taken

* Drainage development

* Stone packing of bunds

* Farm Pond and Storage Structure

•Provision of spillways/Drop Str.

•Increase in water utilization efficiency through low cost technology

Treatment options for different types of lands- Bahal (low land)

Drainage Development

Water Storage structures

Farm Pond in lower reaches

Provision of spillway/drop structure in lower reaches

Drop Structure Drop Structure with silt trap

Stone Packing of Bunds

Increasing water utilization efficiency through low cost device

Micro irrigation pressure pump

Micro irrigation bucket Low cost portable KB pump

Rope washer pump

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