2. S o i l is a natu ral b od y
cons is ting of laye rs (
s oil h orizons )
of m ine ral cons titu e nts
of variab le
th ickne s s e s , wh ich
d iffe r from th e p are nt
m ate rials in
th e ir p h ys ical, and
ch e m ical,
ch aracte ris tics .

3. • Wh at is th e s oil
com p os e d of?
• S oil is m ad e u p of two
m ain com p one nts :
• Tiny b its of m ine ral
p article s , wh ich inclu d e s
s alts of iron, calciu m ,
p otas s iu m , m agne s iu m
and p h os p h oru s , e tc.
• Th e oth e r com p one nts is
h u m u s , wh ich is d ark
b rown in color & cons is ts
of d e caying re m ains of
p lants & anim als .

4. • Bacte ria conve rt nitroge n of th e air into
nitroge n com p ou nd s , wh ich can b e u s e d
b y p lants .Th is is known as F ixing of
nitroge n
F ixing of
nitroge n

5. • Was s oil p re s e nt on e arth at th e
tim e of its form ation?
• N o, long ago, th e grou nd was
m os tly s olid rock. O ve r m illions of
ye ars , th is rock got p artially
ch ange d into s oil b y th e p roce s s
known as we ath e ring.
• Th e s u rface rocks b re ak d own into
s m alle r p ie ce s th rou gh a p roce s s
of we ath e ring and is th e n m ixe d
with m os s and organic m atte r.
O ve r tim e th is cre ate s a th in laye r
of s oil. P lants h e lp th e
d e ve lop m e nt of th e s oil. H ow? Th e
p lants attract anim als , and wh e n
th e anim als d ie , th e ir b od ie s
d e cay. D e caying m atte r m ake s
th e s oil th ick and rich . Th is
continu e s u ntil th e s oil is fu lly
form e d . Th e s oil th e n s u p p orts
m any d iffe re nt p lants

6. We ath e ring is th e p roce s s of
th e b re aking d own rocks .
Th e re are two d iffe re nt typ e s
of we ath e ring.
P h ys ical we ath e ring and
ch e m ical we ath e ring.
In p h ys ical we ath e ring it We ath e ring
b re aks d own th e rocks , b u t in rocks .
wh at it's m ad e of s tays th e
s am e .
In ch e m ical we ath e ring it s till
b re aks d own th e rocks , b u t it
m ay ch ange wh at it's m ad e
of. F or ins tance , a h ard
m ate rial m ay ch ange to a
s oft m ate rial afte r ch e m ical

7. • H ave you e ve r s e e n a d e e p h ole
in th e grou nd , s u ch as th at d u g
u p for laying th e fou nd ation of
b u ild ing?
• You m ay h ave notice d th at s oil
ch ange s colou r as one goe s
d e e p e r. Th e s ize of th e b its of
rocks ch ange s to. Th is are th e
laye rs on s oil.
• Th e m ain laye rs of s oil are
Top s oil, S u b s oil & th e p are nt
rock.

8. • Top s oil ( A-h orizon)
• H u m u s and th e s m alle s t
p article s of rock form th e
u p p e r laye r of s oil calle d
top s oil or A-h orizon
• Th e p re s e nce of h u m u s give s
it a d ark colou r.
• It is th e laye r containing th e
m os t nu trie nts for p lants .
• H u m u s m ake s th is laye r
p orou s and fe rtile .

9. S u b s oil (B-h orizon)
• Th is is th e laye r b e low th e
top s oil.
• S u b s oil d oe s not ave m u ch
h u m u s and is ,
• th e re fore , ligh te r in colou r th e n
top s oil.
• It is m ad e u p m os tly of rock b its
and s om e nu trie nts , s u ch as
s olu b le m ine rals and iron
oxid e s .
• R ainwate r colle cts in th is laye r.

10. • P are nt rock (C -h orizon)
• Be low th e s u b s oil is th e
p are nt rock or C -h orizon,
wh ich cons is ts of s m all
p ie ce s of rocks with cracks
& cre vice s .
• Th e p article s of rocks fou nd
in s oil com e from
we ath e re d rock in th e C -
h orizon.
• Be low th is is s olid rock
calle d b e d rock.
• It is non p orou s .
• R ainwate r gath e rs ove r it to

11. • S oil is not s im ilar e ve rywh e re . S oil is
clas s ifie d into variou s typ e s b as e d on th e
ap p e arance and p rop ortion of p article s .
• S a n d y s o il
• C la y s o il
• L o a m y s o il

12. P rop e rtie s of s and y s oil: P rop e rtie s of clay P rop e rtie s of loam y
s oil: s oil:
If th e s oil is m ad e of a It is m ad e of a It is a m ixtu re
gre ate r p rop ortion of b ig re lative ly h igh of s a n d , s o i l
p article s , it is calle d p rop ortion of f i n e a n d s ilt .
s and y s oil.
p a r t ic le s . S ilt
Th e s a n d
p a r t i c l e s are
Th e s e s oils h ave p a r t i c l e s are
re lative ly l a r g e . Th e y ve ry l e s s p re s e nt b e twe e n th e
cannot fit clos e ly s p a c e b e twe e n p article s of s and and
toge th e r. p article s . s oil.
Th e re are large s p ace s Be cau s e th e p article s It als o
b e twe e n th e m . Th e s e are s m alle r in s ize , contains h u m u s ,
p lace s are fille d with air. wate r can b e trap p e d and is , th e re fore ,
Th e re fore , in th is typ e in th e tiny gap s cons id e re d th e b e s t
of s oil, wate r ab s orp tion b e twe e n th e m . fo r th e
is ve ry h igh as th e g ro w th o f
wate r p as s e s qu ickly C lay s oils

13. • If you s p ill wate r on th e ce m e nt floor of you r
h ou s e , it s tays th e re for a long tim e . h owe ve r, if
you s p ill wate r on th e grou nd ou ts id e th e h ou s e ,
it qu ickly ge ts ab s orb e d in th e s oil. Th is is
b e cau s e wate r can p e rcolate into th e s oil, b u t
not into ce m e nt.
• R ainwate r th at p e rcolate s th rou gh th e s oil
colle cts ab ove b e d rock.
• Th is is natu ral le ve l of grou nd wate r is calle d th e
wate r tab le .

14. • N ow le t u s s e e wh ich kind of s oil ab s orb s m ore
wate r.
• S and y s oil ab s orb s le s s wate r and allows m ore
wate r to p e rcolate .
• C laye y s oil ab s orb s m ore th an s and y s oil , and
allows le s s wate r to p e rcolate .
• We h ave alre ad y s e e n th at s and y s oil cannot
ab s orb s m u ch wate r b e cau s e of th e large
s p ace s b e twe e n th e s oil p article s . O n th e oth e r
h and , claye y s oil ab s orb s and re tains lot of
wate r.

15. • C lim atic factors as we ll as th e com p one nts of th e s oil
d e te rm ine th e typ e s of ve ge tation and crop s th at grow in
a p articu lar are a.
• C e re als like w h e a t a n d g r a m are grown
in c l a y a n d l o a m y s o i l s , b e cau s e th e s e s oils
h ave b e tte r wate r re te ntion cap acity.
• S oils rich in c l a y and organic m atte r with good wate r
re te ntion cap acity are id e al for p a d d y .
• L o a m y s o i l s , wh ich d rain wate r e as ily, are s u itab le
for le ntils a n d o t h e r p u l s e s .
• F or c o t t o n , l o a m y o r s a n d y s o i l s are m ore
s u itab le , b e cau s e of th e ir wate r d raining and air logging
cap acity.
• C lay s oils are rich in h u m u s and fe rtile . Th e s e s oils are
ve ry good for wh e at.

16. • A natu ral is anyth ing th at com e s from th e
e arth and is u s e d b y u s . S oil is ou r m os t
im p ortant natu ral re s ou rce . It is u s e fu l to
u s in m any ways :
• We d e p e nd on s oil for food , cloth ing and
s h e lte r.
• We d e p e nd on th e s oil for m ine rals , s u ch
as coal, p e trole u m and natu ral gas .
• We d e p e nd on th e s oil for wate r.

17. • S oil is m ad e of m ine ral p article s , h u m u s ,
air , wate r and living organis m s .
• S oil is form e d b y we ath e ring of rocks b y
th e action of wate r, wind , glacie rs ,
te m p e ratu re , variations , roots of p lants ,
e tc.
• S oil h as th re e m ain laye rs -
• Top s oil (A-h orizon)
• S u b s oil (B-h orizon)
• P are nt rock (C -h orizon)
• S oil is ve ry im p ortant natu ral re s ou rce .

18. H ap p y
le arn in g !
iya
by: Rab
e
Mad
:7 .
th
s
Clas