Unit-II
Eroded and Compacted soils, Flooded soils, Polluted soils
Eroded and Compacted Soils
Excessive soil version in India combined with a consequent high rate of sedimentation in reservoirs and decreased soil fertility has led to grave environmental problems. soil erosion mostly affects practically all kinds of lands such as forest lands, agricultural lands, arid and semi-arid lands, surface mines, roads, construction sites, coastal areas etc. upper layer leaves cause problems.
IIRS 2015 data- 147 m ha. soil erosion
In coastal areas, the Intensity of erosion depends on the velocity of waves, the volume of water, extension of vegetation cover, nature of rocks etc. At high altitudes, it depends on glacial, snow and wind action
Intense erosion happens in arid and semi-arid areas where vegetation cover is scarce.
Types of Erosion
Natural or Geologic erosion
Accelerated
Causes of Water Erosion
Due to dispersive action and transporting power of water.
- Raindrop/Splash Erosion- removal of fairly uniform layer by rainfall and runoff water on lands having a mild slope.
- Rill Erosion- removal of surface soil by running water, with the formation of narrow shallow channels. transition stage b/w sheet and gully erosion
- Gully erosion- removal of soil by running water, with the formation of channels that cannot be smoothed out completely by normal agricultural operations.
-Stream Channel- Erosion It is the scrubbing of material from the water channels and cutting of banks by flowing or running water.
Harmful effects of water erosion
1. Loss of top fertile soil
2. accumulation of sand and other unproductive coarse soil materials
3. silting of drainage and water channels. it causes overflow and flood.
4. silting of lakes and reservoirs.
5. decrease water table
6. fragmentation of lands
Wind Erosion
found in arid and semi-arid areas where rainfall is insufficient
wind erodes soil in three steps
1. Saltation- a process of soil movement in a series of bounces or jumps. particle sizes- 0.05 to -0.5 mm
2. Suspension- floating of small-sized particles in the air stream
3. Surface creep- it is the rolling or sliding of large soil particles along the ground surface.
Best Management practices
Crop rotation
Contour cultivation
Strip cropping
Terraces- constructing bench-like channels enables water to be stored temporarily on slopes to allow sediment deposition and water infiltration.
Grassed Waterways
Diversion structure
drop structures
Effects of soil Erosion
Loss of Arable land- top fertile layer
clogging of waterways - pollutes water bodies, rises water level
Air pollution
Desertification
Destruction of Infrastructure- accumulation of soil sediments in dams
Soil Erosion Prevention
1. Plant Trees on barren lands
2. Add mulch and rocks
3. Mulch matting
4. Put a series of fibre logs
5. A wall at the base of the slope
6. proper drainage in every household
2. Compacted Soils
Densification of soil by removal of air. Compacted soil cannot function healthily, resulting in poor crops.
Have few large pores, less total pore volume and greater density.
It has a reduced rate of both water infiltration and drainage.
Causes
Occurs when density increases by and energy is input into moist or wet soil. The force may be exerted by tyres, tillage tools or animal hooves.
Effects
1. increase density
2. increase strength characteristics
3. Increase load-bearing capacity
5. decrease undesirable settlement
5. increase the stability of slopes and embankments
6. decrease permeability
6. reduce water seepage
8. reduce swelling and shrinkage
9. reduce frost damage
10. reduce erosion damage
Best management practices
- use direct seeding
- reduce the potential development of compacted soils
- take advantage of natural soil processes of wetting-drying and freeze-thaw to minimize compaction.
- use a combination of fibrous and tap-rooted crops in a rotation to penetrate soils, develop deep root channels and add organic matter to the soil.
3. Flooded Soil