Reasons for decline in soil fertility_1.ppt

Soil

1. Reasons for decline in soil fertility

2. Reasons for decline in soil fertility
Soilfertilityisacomponentofoverallsoil
productivitythatdealswithitsavailable
nutrientstatus,anditsabilitytoprovide
nutrientsoutofitsownreservesand
throughexternalapplicationsforcrop
production.
Introduction

3. 1.Lossoftopsoilbyerosion
2.Nutrientmining
3.Physicaldegradationofsoil(poorstructure,compaction,
crustingandwaterloggingetc.
4.Decreaseinorganicmattercontentandsoilbioactivity
5.Lossofnutrientsthroughvariousroutes
6.Soilacidification,salinizationandalkalinization
7.Inefficientsoilmanagement
8.Soilpollution
Reasons for decline in soil fertility
Causes of decline in soil fertility

4. 1.Lossoftopsoilbyerosion
Thetopsoilisrichinnutrientsandorganic
matter.Lossofthefertiletopsoilcomponents
througherosionbywaterandwindresultsin
decreasedfertility.
Soilerosionisverycommoninmanypartsof
thecountry.
Thebasiccausesofsoilerosionaretheresult
ofhumanactivitiessuchasdeforestation,
overgrazingandpoorsoilmanagement.
Reasons for decline in soil fertility

6. Erosion is the movement of weathered rocks
and soil particles from one place to another.

7. THERE ARE FIVE AGENTS
OF EROSION.
GRAVITY
GLACIERS
WIND
WATER
WAVES

8. GRAVITY
EROSION CAUSED BY
GRAVITY IS CALLED
MASS
WASTING .

9. RAPID MASS WASTING
One type of rapid
mass wasting is
LANDSLIDE
which is the
tumbling of dry soil
and rocks downhill

10. RAPID MASS WASTING
Another type is
MUDFLOW
where rain mixes
with the soil to form
mud which moves
downhill

11. RAPID MASS WASTING
Another type is
SLUMP
where a huge
block of rock
slides rapidly
down a hillside.

12. SLOW MASS WASTING
One type of slow mass
wasting is
EARTHFLOW
where a mass of soil
and plant life begin to
slowly move downhill
after a heavy rain.

13. SLOW MASS WASTING
Another type is
CREEP
where soil particles
move slowly
downhill.
This is the slowest.

14. GLACIERS
A
GLACIER
is a large mass of
moving ice and
snow.

15. GLACIERS
Glaciers move
rocks by
PLUCKING
where ice freezes
around a rock and
moves it along as
the glacier moves.

16. GLACIERS
Glaciers also move
rocks by
ABRASION
where rocks are
loosened and moved by
the glacier, causing
scratches on the
bedrock.

17. WIND
Wind moves soil by
DEFLATION
where wind removes
loose material from
the land.
Here smaller sand grains are blown
away from around larger rocks.

18. WATER
Running wateris the
major cause of
erosion.
Water picks up and
carries loose
particles of soil as it
moves downhill.

19. WATER
Water starts out
in tiny grooves
called
RILLS

20. WATER
Rills become wider
and deeper,
called
GULLIES

21. WATER
Gullies turn into
STREAMS
which turn into
RIVERS.

22. WAVES
Waves carry off
small rocks and
sand from the
beach.

23. EROSION
What is the
agent of
erosion in this
picture?
A.

24. EROSION
What is the
agent of erosion
in this picture?
B.

25. EROSION
What is the
agent of
erosion in
this picture?
C.

26. 2.Nutrientmining
Nutrientminingisacceleratedby
imbalancedfertilization.
Removalofmorenutrientsbycropsthan
addedthroughmanuresorfertilizersis
calledasnutrientminingordepletion.
Itisawidespreadproblemin
low-andmediuminput
agriculture.
Atpresent,nutrientminingisa
majorthreattoproductive
sustainablefarming.
Reasons for decline in soil fertility

27. 3. Physical degradation of soil
Highdisturbanceofsoils(tillage)oftenresults
insomestructuraldeterioration,whichcanbe
reversedtodifferentdegrees.
Physicaldegradationofsoil(poorstructure,
compaction,crustingandwaterlogging)
reducessoilfertility.
Soilstructureisavariablesoilpropertythat,
fromanagronomicpointofview,can
improveordeteriorate.
Reasons for decline in soil fertility

28. 2. Nutrient mining
Theproblemismoreacutein
areaswherehighyielding
varietiesofcropsarebeing
cultivated
Reasons for decline in soil fertility
It results in the exhaustion of any
nutrient required in moderate to
large amounts.
Nutrientminingcouldbesevere
inthecaseofN,P,KandS
dependingonsoilnutrient
reservesandtheamounts
replenished.

29. 3. Physical degradation of soil
WaterloggingcauseslossofN
throughdenitrificationof
nitrate.
Figure(ontheleft)
(a)Rootgrowthinasoilwithno
mechanicalimpedanceproblems
(b)Rootgrowthinasoilwith
mechanicalimpedanceproblems
Soilcompactiondecreasesthenumber
oflargepores(>100μm)and,asthese
aretheonesthroughwhichrootsgrow
mosteasily,compactioncanhavean
adverseeffectonrootgrowth(see
Figure).
Reasons for decline in soil fertility

31. 4. Decrease in organic matter content and soil bioactivity
Themicrobialactivitiesinsoildecreasedueto
reducedlevelsoforganicmatter.These
microbialactivitiesplaysignificantrolein
nutrientavailabilityandrecycling.
The decreased levels of organic matter
causes a strong reduction in soil fertility
as it plays several roles in soil.
Decreased organic matter levels results
in poor physical , chemical and
biological properties.
Reasons for decline in soil fertility

32. 5.Lossofnutrientsthroughvariousroutes
Nutrientremovalbycropproducts
comparedwithexternalnutrientinputscan
besimilar,higherorlower.Negative
nutrientbalancesresultwherenutrient
removalsexceednutrientadditions.
Lossesofnutrientsfromsoilcanbe
causedbysoilerosion,leaching,crop
removalorintheformofgases(asin
caseofNandtoalesserextentS).
Reasons for decline in soil fertility

33. 5. Loss of nutrients through various routes
Ammoniavolatilizationfromureaand
someammonium-containingfertilizers
resultsinlossesofnitrogenfromsoil.
Excessiverainfall,orexcessive
irrigation,resultinginthepassageof
waterthroughthesoilprofilethrough
deeppercolationwillcarrywithit
solublenutrients,particularlynitrate,
sulphateandboron,etc.
WaterloggingcauseslossofN
throughdenitrificationofnitrates.
Reasons for decline in soil fertility

34. Picture: Losses of nutrients through different routes from soil
Source: http://wattsupwiththat.com/2009/10/12/fixing-the-nitrogen-cycle-in-climate-modeling/
Reasons for decline in soil fertility

35. 6. Soil acidification, salinization and alkalinization
Factorsresponsibleforsoildegradation
aregenerallyinterrelated.
Iron deficiency in rice at
higher soil pH
Acidification,salinizationor
alkalinizationcausesreductioninsoil
fertility,andeventuallyleadtoproblems
ofnutrientdeficiencies,toxicitiesand
imbalances.
Reasons for decline in soil fertility

36. 7. Inefficient soil management
Excessivesoiltillageleadstoerosionof
thesoil,whichleadstoreducedsoil
fertility.
Poor or inefficient soil management
results in decreased soil fertility.
Improper crop rotations followed
may decrease the soil fertility
tremendously.
Reasons for decline in soil fertility

37. 8. Soil pollution
Thegrowthofusefulsoil
organismsisadverselyaffected,
whicheventuallycausesadecline
inbiologicalsoilfertility.
Soilpollutioncausedby
indiscriminateuseofagro-chemicals
andheavymetalsreducesfertilityof
soilbyaffectingthesoilbiological
properties.
Reasons for decline in soil fertility