2. Index
Topic Slide Topic Slide
No. No.
What is Soil? 4 Sustainable Agriculture 13
through Soil Conservation
Factors of Soil formations 5 Irrigation Techniques 16
Classification Soils 6 Soil Nutrients 17
Alluvial Soil 7 Fertilizers 18
Black Soil 8 The Green Revolution and 19
its Environmental Impact
Red & Yellow Soil 9 Appendix 22
Laterite Soil 10 Bibliography 23
Arid Soil 11 Assessment Sheet 24
3. What is soil?
Top soil
the upper soil layer
Top most layer of earth
crust consisting of Subsoil weathered
organic and inorganic rocks sand and
silt clay
matters is called soil.
Soil is a renewable
resource. Substratum
weathered parent
rock material
Soil is a living system.
It is the medium of plant
growth and
supports different types Unweathered
of living organisms on parent bed rock
the earth.
4. Factors of Soil formations
A. Relief,
B. Parent rock or bed rock,
C. Climate,
D. Time are important factors
in the formation of soil.
E. Actions of running
water, wind and glaciers,
F. Activities of decomposers
etc.
G. Chemical and organic
5. Classification Soils
Major types of Soils
found in India.
• Alluvial Soil
• Black Soil
•Red and Yellow
Soils
• Laterite Soils
• Arid Soils
6. Alluvial Soils
a. Most widely spread: The
entire northern plains are
made of alluvial soil.
b. Deposited by Himalayan river
systems– the Indus, the
Ganga and the Brahmaputra.
c. Alluvial soils as a whole are
very fertile having potash,
phosphoric acid and lime.
d. Regions of alluvial soils are
intensively cultivated.
7. Black Soils
a. These soils are also known as regur soils
or black cotton soil.
b. Climatic condition along with the parent
rock material are the important factors for
the formation of black soil.
c. They are well-known for their capacity to
hold moisture. In addition, they are rich in
soil nutrients.
d. These soils are generally poor in
phosphoric contents.
e. These soils are sticky when wet and
difficult to work on unless tilled
immediately after the first shower or
8. Red and Yellow Soils
a. Red soil develops on crystalline igneous
rocks in areas of low rainfall in the
eastern and southern parts of the Deccan
plateau.
b. Yelllow and red soils are also found in
parts of Orissa, Chhattisgarh middle
Ganga plain.
c. These soils develop a reddish colour due
to diffusion of iron in crystalline and
metamorphic rocks.
d. It looks yellow when it occurs in a
hydrated form.
9. Laterite Soils
a. Laterite has been derived from the Latin
word ‘later’ which means brick.
b. This is the result of intense leaching due to
heavy rain. Humus content of the soil is low
because most of the micro organisms,
particularly the decomposers, like bacteria,
get destroyed due to high temperature.
c. These soils are mainly found in Karnataka,
Kerala, Tamil Nadu, Madhya Pradesh, and
the hilly areas of Orissa and Assam.
d. Red laterite soils in Tamil Nadu, Andhra
Pradesh and Kerala are more suitable for
crops like cashew nut.
10. Arid Soils
a. Arid soils range from red to brown in colour.
b. They are generally sandy in texture and
saline in nature.
c. In some areas the salt content is very high
and common salt is obtained by evaporating
the water.
d. Due to the dry climate, high
temperature, evaporation is faster and the soil
lacks humus and moisture.
e. The lower horizons of the soil are occupied by
Kankar because of the increasing calcium
content downwards.
f. The Kankar layer formations in the bottom
horizons restrict the infiltration of water.
g. After proper irrigation these soils become
cultivable as has been in the case of western
Rajasthan.
11. Forest Soils
a. These soils are found in the hilly and
mountainous areas where sufficient rain
forests are available.
b. The soils texture varies according to the
mountain environment where they are
formed. They are loamy and silty in
valley sides and coarse grained in the
upper slopes.
c. In the snow covered areas of
Himalayas, these soils experience
denudation and are acidic with low
humus content.
d. The soils found in the lower parts of the
valleys particularly on the river terraces
and alluvial fans are fertile.
12. SUSTAINABLE AGRICULTURE
THROUGH SOIL CONSERVATION
Terracing, contour
planting, strip
cropping, alley
cropping, and
windbreaks can
reduce soil erosion.
13. Strip Cropping – a row
crop such as corn
alternates in strips with
another crop that
completely covers the
soil, reducing erosion. It
catches and reduces
water runoff and helps
prevent the spread of
pests and plant
14. Cover Cropping (alley cropping) – several
crops are planted together in strips or alleys
between trees and shrubs that can provide
shade (which reduces water loss by
evaporation) and helps to retain and slowly
release soil moisture.
15. Irrigation Techniques
Conventional center-pivot irrigation- allows
80% of the water input to reach crops
Gravity-flow irrigation- Valves that send
water down irrigation ditches.
Drip irrigation- Can raise water efficiency to
90-95% and reduce water use by 37-70%.
Floodplain irrigation- allowing the natural
floods to irrigate the crops. Soils in flood
zones tend to be nutrient rich and fertile.
16. Soil Nutrients
Macronutrients are larger in
atomic structure. Ex. Nitrogen,
Phosphorus & Potassium.
Micronutrients
These are smaller in atomic
structure. Plants need them in
small amounts.
17. Fertilizers
Organic Fertilizers – animal manure, crop
residues, bone meal, and compost
Inorganic Fertilizers – man-made from chemical
compounds
Benefits – exact compositions are known;
they are soluble & thus immediately available
to the plant
Costs – quickly leach away; this pollutes the
water; doesn’t help the water holding capacity
of the soil like organic fertilizers do.
18. THE GREEN REVOLUTION AND ITS
ENVIRONMENTAL IMPACT
Since 1950, high-input agriculture has produced
more crops per unit of land.
In 1967, fast growing dwarf varieties of rice and
wheat were developed for tropics and subtropics.
19. THE GREEN REVOLUTION AND ITS
ENVIRONMENTAL IMPACT
Lack of water, high costs for small farmers, and
physical limits to increasing crop yields hinder
expansion of the green revolution.
Since 1978 the amount of irrigated land per
person has declined due to:
Depletion of underground water supplies.
Inefficient irrigation methods.
Salt build-up.
Cost of irrigating crops.
20. THE GREEN REVOLUTION AND ITS
ENVIRONMENTAL IMPACT
Modern agriculture has a greater harmful
environmental impact than any human activity.
Loss of a variety of genetically different crop and
livestock strains might limit raw material needed
for future green and gene revolutions.
In the U.S., 97% of the food plant varieties available
in the 1940 no longer exist in large quantities.
21. Bibliography
Birkeland, Peter W. Soils and Geomorphology, 3rd
Edition. New York: Oxford University Press, 1999.
Chesworth, Edited by Ward (2008), Encyclopedia of soil
science, Dordrecht, Netherland: Springer, xxiv, ISBN 1-
4020-3994-8
Voroney, R. P., 2006. The Soil Habitat in Soil
Microbiology, Ecology and Biochemistry, Eldor A. Paul
ed. ISBN=0-12-546807-5
James A. Danoff-Burg, Columbia University. The
Terrestrial Influence: Geology and Soils
Janet Raloff. Dirt Is Not Soil. ScienceNews July 17th,
2008)
Taylor, S. A., and G. L. Ashcroft. 1972. Physical
Edaphology
