Rearing technique of lac insect and their management

1. Soil Erosion

2. Soil Erosion
❖ Process of detachment of soil particles from its parent
body and transportation by wind and water.
❖ Natural or geological erosion – Erosion of land in its
natural state, undisturbed by human activities. The soil
loss in this erosion is compensated by soil forming process
by natural weathering.
❖ Accelerated erosion- erosion taken place by activities of
human and animals. The soil loss in this erosion is faster
than soil forming process by natural weathering.

3. Soil Erosion
❖ In India the rate of soil erosion is 16.4 t/ha/year
❖ The permissible soil loss limit is 11.2ct/ha/year.

4. FACTORS RESPONSIBLE FOR EROSION
1. Excessive deforestation
2. Improper agricultural practices
3. Over grazing
Evil effects of erosion
1) Loss of productive or fertile soil
2) Deposition of sand on productive land
3) Silting of lakes and reservoirs

5. According to Erosion Agents:
❖ Water Erosion: Water erosion is seen in many parts of
the world. In fact, running water is the most common
agent of soil erosion. This includes rivers which erode
the river basin, rainwater which erodes various
landforms, and the sea waves which erode the coastal
areas.
❖ (i) raindrop erosion, (ii) sheet erosion, (iii) rill erosion,
(iv) gully erosion, (v) stream bank erosion

6. (2) Wind Erosion
❖Wind erosion is most often witnessed in dry areas
wherein strong winds brush against various landforms,
cutting through them and loosening the soil particles,
which are lifted and transported towards the direction in
which the wind blows.
❖The best example of wind erosion are sand dunes and
mushroom rocks structures, typically found in deserts.

7. (3) Glacial Erosion
❖ Glacial erosion, also referred to as ice erosion, is
common in cold regions at high altitudes. When soil
comes in contact with large moving glaciers, it sticks
to the base of these glaciers.

8. (4) Gravitational Erosion
❖ It is basically the mass movement of soil due to
gravitational force.
❖ The best examples of this are landslides and slumps.
While landslides and slumps happen within seconds,
phenomena such as soil creep take a longer period for
occurrence.

9. FACTORS INFLUENCING WATER EROSION
❖ Major factors are climate, topography, vegetation and soil.
❖ E=f(C,T,V,S)
❖ Climate (C) : Climatic factors include rainfall, temperature
❖ Topography (T): Degree and length of topography are
two main factors. The velocity of runoff is mainly
influenced by topography.
❖ Vegetation (V): The effects of vegetation for erosion are
i. Interception of rainfall:

10. FACTORS INFLUENCING WATER EROSION
❖ Major factors are climate, topography, vegetation and soil.
❖ E=f(C,T,V,S)
❖ Climate (C) : Climatic factors include rainfall, temperature
❖ Topography (T): Degree and length of topography are
two main factors. The velocity of runoff is mainly
influenced by topography.
❖ Vegetation (V): The effects of vegetation for erosion are
i. Interception of rainfall:

11. FACTORS INFLUENCING WATER EROSION
ii. Decrease in runoff velocities
iii. Root effects
v. Transpiration effects

12. vegetation
• Soil detachment rate on bare soil under forest canopies
can be 2-4 times higher than those on open ground.
• A raindrop falling on leaves slowly coalesces and bigger
the drops fall as leaf drips.
• Some of the intercepted water flows along the stem to the
ground, known as stem flow
• Some amount of rainfall directly reaches the soil if crop
cover is not complete, known as through fall.

13. FACTORS INFLUENCING WATER EROSION
ii. Decrease in runoff velocities
iii. Root effects
iv. Biological influences
v. Transpiration effects
Soil (S) : The physical properties of soil that influence soil
erosion includes structure, texture, organic matter,
moisture content, compactness as well as chemical and
biological characteristics of soil.

14. Soil
The quantity of soil lost by erosion is proportional to the
volume of water flow in the runoff.
Velocity √slope %
• If velocity doubles Erosive power will be 4times
(square)
• If velocity doubles Quantity of soil to be transported will
increase 32 times (5 squares)
• If velocity doubles Particle size to be transported will
increase 64 times (6 squares)

15. Physics of rainfall
1. Annual Distribution of Rainfall
2. Rainfall Intensity
3. Raindrop Size
Rainfall Erosivity - Rain erosivity, the potential ability of rain to
cause erosion, is a function of the physical characteristics of
rainfall.
Soil Erodibility - It is the susceptibility of the soil to erosion or is
the reciprocal of its resistance to erosion Silt and very fine sand
fraction increases the erodibility and clay fraction decreases the
erodibility of soil.

16. Types of Water Erosion
➢ Splash Erosion:
➢ The soil may be splashed into the air up to a height of 50
to 75 cm depending upon the size of rain drops.
➢ At the same time the soil particles also move horizontally
as much as 1.50 m on level land surface.

18. Sheet Erosion:
•Sheet erosion may be defined as more or less uniform
removal of soil in the form of a thin layer or in “sheet” form
by the flowing water form a given width of sloping land
•In the sheet erosion two basic erosion processes are
involved.

20. Rill Erosion
• This type of water erosion is formed in the cultivated fields where the
land surface is almost irregular.
• This surface flow containing soil particles in suspension form moves
ahead and forms micro channels and rills

22. Gully Erosion
❖ Rills are small in size and can be leveled by tillage
operations. When rills get larger in size and shape due
to prolonged occurrence of flow through them and
cannot be removed by tillage operation, these are called
gullies
❖ Large gullies and their network are called ravines. It
is the advanced and last stage of water erosion.
❖ In other words it is the advanced stage of rill erosion.

24. Gully Erosion classification
❖ Very small gullies- Deep up to 3m
width- not greater than 18
❖ Small – depth upto 3 m , width >18m, side slope- 8-15%
❖ Medium gullies- b/w 3-9m, width not less than 18m, side
slope 8-15%
❖ Deep and narrow gullies- >9m, width vary, slope- steep

26. Stream Bank Erosion
•Stream bank erosion is defined as the removal of stream bank soil by water
either flowing over the sides of the stream or scouring from there.

28. Sea-shore Erosion
•It is also called coastal erosion.
•Sea shore erosion is the wearing away of land and the removal of beach or
dune sediments by wave action, tidal currents, wave currents, or drainage.
•Waves, generated by storms, wind or fast moving motor craft, cause coastal
erosion which may take the form of long-term losses of sediment and rocks,
or merely the temporary redistribution of coastal sediments.

30. Landslide Erosion
❖ When gravity combines with heavy rain or earthquakes, whole
slopes can slump, slip or slide.
❖ Slips occur when the soil (topsoil and subsoil) on slopes
becomes saturated. Unless held by plant roots to the underlying
surface, it slides downhill, exposing the underlying material.

32. Agronomical Measures of Water Erosion Control
❖ Contour Cropping
❖ Contour cropping involves
planting crops across the slope
instead of up and down the
slope

33. • Strip cropping is the practice of
growing strip of crops having poor
potential for erosion control, such as
root crop (intertilled crops), cereals,
etc., alternated with strips of crops
having good potentials for erosion
control, such as fodder crops,
grasses, etc., which are close
growing crops
Strip Cropping

34. • The sequence of crops grown in an area over a period of time is termed
as cropping system.
• This system should be such that the soil is covered with vegetation
during heavy rainfall period.
• Cowpea and green gram covers about 85 % soil surface, crop rotation
with lucerne reduces soil loss about 13%.
3) cropping systems

35. • Crops like groundnut, soybean, green gram etc., are commonly used in
crop rotation. These crops are having soil binding capacity and act as
erosion resisting crop.
4) crop rotation

36. • Mixed cropping is the system of showing more than one crop together
on the same land. Mixed crops varying in root systems helps in
utilizing the plant nutrients in the profile. Erosion permitting and
erosion resisting crops are raised in the same land in mixed cropping.
5) Mixed cropping

37. • Vegetative barrier plantation is also called "buffer strip cropping".
• These buffer strips are usually 2-4 m wide and are placed at 10-20 m
interval.
• Vetiver grass (Vetiveria zizanoides) has been found to have desirable
characteristics for trapping sediments, thus naturally tending to reduce
the land slope between the barrier strips.
• The local grasses with an erect growth habit of inter-woven stems viz.
babbar, kanha and napier bajra, act like a porous filter are more effective
in reducing erosion.
Vegetative Barriers

38. Mulching
•Mulch is any material applied on soil surface to check
evaporation and improve soil water.
•Defined as the any natural or synthetic applied layer of
plant residues or other material on the surface of soil.
•They also help in improving the infiltration capacity by
maintaining a conductive soil structure at the top
surface of land.

39. Types of mulches
1. Synthetic mulch - resins, asphalt emulsions, latex
and cut back asphalt, canvas etc.
2. Conventional mulch
3. Stone mulch
4. Organic mulch

40. Types of mulching material
1. Cut grasses or foliage
2. Straw materials
3. Wood chips
4. Saw dusts
5. Papers
6. Stones
7. Plastics

41. cover cropping
the process of allowing growth of crops having
economical value so as to afford productive cover to
the bare space in the cultivated lands, without
interfering or suffocating the growth of the main
crops grown in the field is called cover cropping.
Example: Leguminous crops, sweet potato, pumpkin
and groundnut.

42. B. Mechanical methods of water erosion
control
•CONTOUR BUNDING
•Contour bunding is the construction of small bund
across the slope of the land on a contour so that the
long slope is cut into a series of small ones and each
contour bund acts as a barrier to the flow of water,
thus making the water to walk rather than run, at the
same time impounding water against it for increasing
soil moisture

43. B. Mechanical methods of water erosion
control
•For rolling and flatter lands having slopes from 2 to
6% contour bunding is practiced.
•GRADED BUNDS
•Graded bunds are constructed in medium to high
rainfall areas having an annual rainfall of 600 mm and
above and in soils having poor permeability (or) those
having crust forming tendency (black soils), and in
the lands having slopes between 2% and 6%.

44. Terracing

45. B. Mechanical methods of water erosion
control
•BENCH TERRACING
•Bench terracing is one of the most popular
mechanical soil conservation practices.
•It consists of construction of step like fields along
contours by half cutting and half filling.
•Bench terraces are normally constructed in lands
having slope between 16% and 33%.

46. Slopes
❖Agronomic measures – <2%
❖Mechanical measures- >2%
❖Contour bunding- 6%
❖Graded bunding- 2-10%
❖Bench terracing- 16-33%
❖Zing terracing – 3-10%

47. Wind erosion
•High velocity winds strike the bare lands (having no
cover), with increasing force.
• Fine, loose and light soil particles blown from the
land surface are taken miles and miles away and
thereby, causing a great damage to the crop
productivity.

48. •Wind erosion damages land and natural vegetation by
removing soil from one place and depositing it at
another location.
•It causes soil loss, dryness and deterioration of soil
structure, nutrient and productivity losses and air
pollution.

49. Mechanics of Wind Erosion
•The overall occurrence of wind erosion could be
described in three distinct phases.
These are:
1. Initiation of Movement
2. Transportation
3. Deposition

50. Initiation of Movement
❖The soil particles are first detached from their place by the
impact and cutting action of wind.
❖These detached particles are then ready for movement by
the wind forces.
❖After this initiation of movement, soil particles are moved
or transported by distinct mechanisms

51. Transportation
❖The transportation of the soil particles are of three distinct
types and occur depending upon size of the soil particles.
❖Suspension, Saltation, and surface creep are the three types
of soil movement or transport which occur during wind
erosion.

53. Suspension
❖It occurs when very fine dirt and dust particles are lifted
into the atmosphere.
❖The soil particles of less than 0.1 mm size are subjected to
suspension and around 3 to 4 % of soil weights are carried by
the suspension method of soil transport under the wind
erosion.

54. Saltation
❖Saltation movement is caused by the pressure of the wind
on soil particles as well as by the collision of a particle with
other particles.
❖Soil particles (0.1 to 0.5 mm) move in a series of bounces
and/or jumps.
❖Depending on soil type, about 50 to 75% of the total
weight of soil is carried in saltation.

55. Surface Creep
❖The large particles which are too heavy to be lifted into the
air are moved through a process called surface creep.
❖In this process the largest of the erosive particles having
diameters between 0.5 to 2 mm are transported and around 5
to 25% of the total soil weights are carried in this fashion.

57. Deposition
❖Deposition of soil particles occurs when the gravitational
force is greater than the forces holding the particle in the air.
❖This generally happens when there is a decrease in the
wind velocity caused by vegetative or other physical barriers
like ditches or benches. Raindrops may also take dust out of
air.

58. Wind Erosion Control
Three basic methods can be used to control wind erosion:
•Maintain Vegetative Cover (Vegetative Measures)
•Roughen the Soil Surface by Tillage Practices (Tillage
Practices or may be called Tillage Measures)
•Mechanical or Structural Measures (Mechanical Measures)

59. Vegetative Measures
•Vegetative measures can be used to roughen the whole
surface and prevent any soil movement.
•The aim is to keep the soil rough and ridged to either
prevent any movement initially or to quickly trap bouncing
soil particles in the depressions of the rough surface.
•A cover crop with sufficient growth will provide soil
erosion protection during the cropping season.

60. (a) Strip cropping
•Strip cropping for wind erosion control consists of a
systematic alternate arrangement of erosion-susceptible and
erosion resistant crops in relatively narrow strips whose
length runs perpendicular to the direction of the prevailing
erosion winds.

61. (b) Crop rotation
•Good management techniques are important.
•A good crop rotation that will maintain soil structure and
conserve moisture should be followed as for as possible.
•However, deficient moisture often limits the use of soil
improving and soil conserving crop such as legumes and
grasses.

62. (c) Stubble mulching
•Stubble mulching is the practice of maintaining crop
residues at the ground surface-offers good protection from
soil blowing. Crop residues like wheat, straw, stalks of pearl
millet, maize, sorghum, etc., are left on the ground.

63. Mechanical Measures
❖ This method consists of some mechanical obstacles,
constructed across the prevailing wind, to reduce the
impact of blowing wind on the soil surface.
i) wind breaks
ii) shelter belts.

64. • This is a permanent vegetative measure
which helps in the reduction of wind
erosion.
• It is most effective vegetative measure
used for controlling severe wind erosion.
• The term wind break is defined as any
type of barrier either mechanical or
vegetative used for protecting the areas
like building apartments, orchards or
farmsteads etc. from blowing winds.
Wind Breaks

65. Shelter Belts
❖A shelterbelt is a longer barrier than
the wind break, is installed by using
more than two rows, usually at right
angle to the direction of prevailing
winds.
❖The rows of belt can be developed by
using shrubs and trees.
❖ It is mainly used for the conservation
of soil moisture and for the protection
of field crops, against severe wind
erosion

66. ❑Shelterbelt is more effective for reducing the
impact of wind movement than the wind break.
Apart from controlling wind erosion, it provides
fuel, reduces evaporation and protects the
orchard from hot and cold winds.

67. The USLE is an erosion prediction model for estimating long term averages of
soil erosion from sheet and rill erosions from a specified land under specified
conditions (Wischmeier and Smith, 1978)
The Universal Soil Loss Equation
(USLE)

68. • A = Soil loss per unit area in unit time-t, ha-1 yr -1,
• R = Rainfall Erosivity factor
• K = Soil Erodibility Factor (0.2-0.3)
• L = Slope Length factor (22m)
• S = Slope Steepness factor (9%)
• C = Cover Management factor (0.1 – vegetative cover, 1 barren
land)
• P = Support Practice factor

69. Estimation of Soil Loss Due to Wind Erosion
Where, E is soil loss by wind erosion
• I is soil cloddiness factor
• R is surface cover factor,
• K is surface roughness factor
• F is soil textural class factor
• C is factor representing local wind condition
• D is wind direction factor
• B is wind barrier factor
• W is field width factor

70. Wind Erosion equation
• USA based
E= f(I,K,C,L,V)
E= Estimated soil loss ton/ha/year
f-= functional relation
I= Soil erodibility index
K= ridge roughness factor
C- climate factor
L= length of unsheltered eroded field
V= vegetative factor

71. Land capability classification
Class 1- it has no limitation, good for intensive crop cultivation.
• Crop management practices like fertilizer, manure, crop rotation etc.
• Alluvial soils of indo gangetic plains.
Class II- it has some limitations such as gentle slope, moderate erosion
hazard, slightly alkali or saline soil.
• Conservation tactics- strip cropping, contour tillage, crop rotation
• Eg- black soil, deep red
Class III- severe limitation steep slope, high erosion hazard, slow water
permeability and restricted root zone.

72. Land capability classification
• Fertility status of such soil is poor.
• Special conservation measures
• Eg- slightly saline, black.
Class iv
• Very severe limitation on choice of crops
• Ocassional cultivation
• Used for pasture/hay
• Shallow soil, saline soil, alkaline soil.
Class v
• Stony or rocky soil and pond area where drainage is not possible
• Used for grazing and forestry
• Arid and rocky soil

73. Land capability classification
Class VI
Have some limitations on use for grazing/forestry
Class VII
Severe limitation on use for grazing/forestry
Class VIII
Not suitable for any kind of crop production
Restricted to wild life, aesthetic purpose and watershed protection.
Eg-sandy beaches, river washes etc

74. Dealing with protection of soil against physical loss by
erosion or against chemical deterioration i.e. excessive
loss of nutrients either natural or artificial means is
known as?
(a) Soil Formation
(b) Soil Erosion
(c) Soil Accumulation
(d) Soil Conservation
(e) Soil Degradation
(d) Soil Conservation

75. Mulch tillage is practiced to minimise which of the
following? (BHU PET 2016)
(a) Moisture loss from soil
(b) Sediment yield from field
(c) Splash Effect
(d) Sheet Erosion
(e) Ravine Erosion
(a) Moisture loss from soil

76. A system of tillage in which organic residues are not
inverted into the soil and used as a protective cover
against erosion and evaporation losses of soil moisture?
(MP-RAEO)
(a) Conservational Tillage
(b) Conventional Tillage
(c) Mulching
(d) A and C Both
(e) All of these
(d) A and C Both

77. In Universal Soil Loss Equation, A = R × K × L × S ×
C × P, what is S? (BHU PG -2018) ( ICAR JRF 2021)
(a) Soil Erodibility
(b) Soil Erosivity
(c) Soil Cover
(d) Soil Steepness
(e) Soil erosion control factor
(d) Soil Steepness

78. In universal soil loss equation (A=RKL.SCP) K
denotes? (IBPS AFO)
(a) Soil erodibility Factor
(b) Slope gradient
(c) Rainfall Factor
(d) Soil Erosivity
(e) Soil Cover
(a) Soil erodibility Factor

79. Deforestation generally decreases (Raj. PG 2019)
(a) Rainfall
(b) Erosion
(c) Both A and B
(d) None of these
(a) Rainfall

80. Wind Erosion is common in which of the following
zones?
(a) Humid
(b) Semi Humid
(c) Arid
(d) Semi Arid
(e) Both C and D
(e) Both C and D

81. Most spectacular symptom of soil erosion is
(a) Sheet erosion
(b) Gully erosion
(c) Rill erosion
(d) Landslides
(b) Gully erosion

82. Soil erosion depends on
(a) Type of vegetation
(b) Type of soil
(c) Temperature
(d) Both a and b
(d) Both a and b

83. According to land use capability classification, classes
suitable for agriculture are
(a) I, II, III and IV alone
(b) I and II
(c) I to VIII
(d) I to VI alone
(a) I, II, III and IV alone

84. Bench terracing is necssary in soils having
(a) 16-33% slope
(b) 50% slope
(c) 5% slope
(d) 6-13% slope
(a) 16-33% slope

85. Muddy runoff from the field is an indication of?
(a) Splash Erosion
(b) Gully Erosion
(c) Rill Erosion
(d) Sheet Erosion
(e) Ravine Erosion
(d) Sheet Erosion

86. Water erosion follows the sequence? (ICAR-JRF 2021)
(a) Splash > Rill > Gully > Sheet
(b) Splash > Sheet > Rill > Gully
(c) Splash > Gully > Sheet > Rill
(d) Gully > Sheet > Rill > Splash
(e) Sheet > Splash > Rill > Gully
(b) Splash > Sheet > Rill > Gully

87. Wind erosion is common in the state of ?( BHU PET
2016)
(a) West Bengal
(b) Tamil Nadu
(c) Karnataka
(d) Andhra Pradesh
(e) Rajasthan
(e) Rajasthan

88. Which is the best method to prevent soil erosion? PRE
PG (2020)
(a) Deforestation
(b) Afforestation
(c) Heavy Rainfall
(d) Water Logging
(e) None of these
(b) Afforestation

89. The ability of soil to get eroded is called? (CUET PG
2022)
(a) Erosivity
(b) Rigidity
(c) Erodibility
(d) Conservity
(e) None of these
(c) Erodibility

90. The erosion of soil particles between 0.1 to 0.5 mm
diameter by wind is termed as (PRE PG Exam 2019)
(a) Interruption
(b) Saltation
(c) Suspension
(d) Surface Creep
(e) Sheet Erosion
(b) Saltation

91. The readiness of soil to erode is called?
(a) Erodibility
(b) Erosivity
(c) Susceptibility
(d) Buffer Capacity
(a) Erodibility

92. Thank You