2. FERTILIZERS
Substances which are added to the soil to increase its
fertility are called Fertilizers.
Many natural substance like leaves, cow dung, bone meal
compost etc are used to make up the deficiency of
nitrogen , phosphorus and potassium in soils. These
substance are known as natural fertilizers.
Since the demand for fertilizers cannot be met by natural
fertilizers alone, many compounds are manufactured to
provide nitrogen, potassium and phosphorous to plants.
These chemicals are known as artificial or chemical
fertilizers.
3. Important natural inorganic fertilizers are potassium
salts and rock phosphate. The important source of
potassium are wood ash and waste materials of sugar
beet crop.
Potassium salts increase the quantity of crops and
enable the plants to resist the diseases. Other
naturally occurring potassium salts are niter or
saltpeter(Potassium nitrate) carnalities ( containing
potassium chloride)
Rock phosphate is a naturally occurring phosphorous
fertilizer.
6. Mixed fertilizers:-
A fertilizer which contains more than one plant
nutrients is called mixed fertilizer.
Mixed fertilizer Containing nitrogenous,
phosphatic and potash fertilizers in definite
proportions.
Such fertilizers are called NPK fertilizers
7. NPK Value:-
The efficiency of a fertilizer is expressed in terms of NPK
Value. N,P,K stands for Nitrogen, Phosphorous and
Potassium.
It expresses the nitrogen, phosphorous and potassium
contents in terms of elementary nitrogen, P2O5, and K2O
respectively .
Eg: NPK Vlue of 10:5:20 for a mixed fertilizer means that the
particular fertilizer contains 10% nitrogen, 5% P2O5 and 20%
K2O.
9. The increased use of fertilizers to expand
food supplies have come at a large cost to our
environment.
Modern agricultural techniques are typically
wasteful in their use of fertilizers.
10. Often, many farmers add large amounts of
fertilizer or manure at the time of sewing in
order to cover and protect the young plants.
This technique is inefficient, since the young
plants are unable to absorb most of the
nitrogen.
Therefore, much of the nitrogen is lost to the
environment in a number of ways.
11. For example, the nitrate directly leaching
off into the environment as water runs off of
the field is a leading cause.
Once the nitrogen is introduced into the
ground system, the ammonium ions, which
are normally in equilibrium with ammonia
in the soil, are disturbed. This action causes
a disruption in the pH of the soil, which
affects plant growth.
12. Phosphate based fertilizers are also used in
addition to nitrogen based fertilizers.
Unfortunately, as with nitrogen based fertilizers,
there are negative environmental consequences.
The increasing use of phosphate fertilizers has led
to the accumulation of phosphorus in soils. This
causes problems because the means by which
phosphorus is immobilized cannot accommodate
for the additional phosphorus that fertilizers add
to soils.
13. Consequently, high concentrations of
phosphorus flow away with agricultural
runoff.
The toxic effects of phosphorus become
noticeable when agricultural runoff is
deposited in lakes , streams and other water
sources because excessive amount of
phosphorus leads to eutrophication.
14. Eutrophication, a natural process by which lakes,
streams and some estuaries age, is sped up by
activities such as land clearing, production and
application of fertilizers, agricultural runoff and
release of human waste.
The previously mentioned processes result in the
mobilization of nutrients such as nitrogen and
phosphorus into aquatic systems.
These nutrients disrupt aquatic systems by
increasing the growth of unwanted algae and aquatic
weeds. As these organisms die they reduce the
oxygen supply available for other organisms.
15. Without dissolved oxygen in the water, most
organisms cannot survive. The depletion of
oxygen also promotes the conversion of
compounds to their toxic form which may
potentially harm more organisms.
If the fertilizers end up in drinking water,
they can cause health problems for people
17. Biofertilizers are ready to use live
formulates of such beneficial
microorganisms which on application to
seed, root or soil mobilize the availability of
nutrients by their biological activity in
particular, and help build up the micro-
flora and in turn the soil health in general.
18. With the introduction of green revolution technologies
the modern agriculture is getting more and more
dependent upon the steady supply of synthetic inputs
(mainly fertilizers), which are products of fossil fuel
(coal+ petroleum).
Adverse effects are being noticed due to the excessive
and imbalanced use of these synthetic inputs. This
situation has lead to identifying harmless inputs like
biofertilizers.
Use of such natural products like biofertilizers in crop
cultivation will help in safeguarding the soil health and
also the quality of crop products.
19. Benefits from using biofertilizers
•Increase crop yield by 20-30%.
•Replace chemical nitrogen and phosphorus by 25%
.
•Stimulate plant growth.
•Activate the soil biologically.
•Restore natural soil fertility.
•Provide protection against drought and some soil
borne diseases.
20. Advantages of bio-fertilizers
1.Cost effective.
2.Suppliment to fertilizers.
3.Eco-friendly (Friendly with nature).
4.Reduces the costs towards fertilizers use, especially
regarding nitrogen and phosphorus.
21. Types of biofertilizers available
1.For Nitrogen
•Rhizobium for legume crops.
•Azotobacter/Azospirillum for non legume crops.
•Acetobacter for sugarcane only.
•Blue –Green Algae (BGA) and Azolla for low land
paddy.
2.For Phosphorous
•Phosphatika for all crops to be applied with
Rhizobium, Azotobacter, Azospirillum and
Acetobacter
3.For enriched compost
•Cellulolytic fungal culture
•Phosphotika and Azotobacter culture
23. Pesticides are chemical substances used to kill
insects, fungi, rodents,weeds or other living
things which are harmful to plants, animals or
foodstuffs.
Pesticides function as poisons for the
important biological process of insects, fungi
etc which lead to the death of these
organisms.
24. Classification of pesticides
Depending upon the purpose for which the
pesticides are used, they are classified as
follows.
i) insecticides v) algaecide
ii) herbicide vi) molluscicides
iii) fungicides vii) miticides
iv) rodenticides viii) nematocides.
Pesticides may be organic, inorganic, or compounds
obtained from natural products.
25. Insecticides:-
Chemicals used to kill the insects are
called insecticides. Insecticides are
further classified into Stomach poisons,
contact poison and fumigants .
26. Stomach poisons are absorbed through the
digestive system of the insects. These are
effective against insets like caterpillar. Eg; Acid
lead arsenate , cryolite ,sodium fluoride.
Contact poisons affects the insects on contact.eg:
DDT,BHC,Dieldrin(Chlorinated hydrocarbon)
melathion,parathion(Organo phosphate
compounds).
Fumigents aregaseous chemicals which kills
insects by entering directly to the respiratory
systems. Eg: Hydrogen cyanide, naphthalene
,nicotine
27. Herbicides:-
Herbicides are used to destroy weeds (destroy
the growth of plants).
eg: 2,4 D (2,4 dichloro phenoxy acetic acid)
2,4,5 T (2,4,5 trichloro phenoxy acetic acid ).
28. Fungicides:-
Fungicides are are chemicals which are
used to prevent the growth of fungi or
eradicate fungal diseases of plants.
Eg: Lime, sulphur, formalin etc
29. Rodenticides:-
These are chemicals used to kill rats and mice
which destroy crops and spread deseases.
Eg: Sodium fluoroacetate, Zinc phosphide etc
30. Algaecide:-
These are chemicals added to water to
destroy algae.
Eg: copper sulphate
Molluscicides:-
These are chemicals used to destroy
mollusks like snails , slugs etc
eg: Copper sulphate, metaldehyde etc
31. Miticides:-
Chemicals used to destroy mites are called
miticides .
eg: organo phosphates.
Nematocides:-
These are chemicals used for the distruction of
nematodes like round worms, thread worms
etc .
eg: dimethoate
33. The excessive use of pesticides have created tremendous adverse
effects on environment
1) Environmental pollution:-
Pesticides drained to water bodies causes water
pollution . hence water in river, lakes and seas gets
polluted which becomes hazardous to aquatic
animals like fishes.
Pesticides may also washed down to ground water
which pollute drinking water. During the spraying
of pesticides it may reach in to atmosphere and
pollute the air.
34. 2) Certain pesticides such as DDT, BHC etc
persisted in the environment accumulated in
blood,milk and fat of animals.Beyond certain
permitted levels, they are very dangerous to
human beings and animals
3) Pesticides may kill the friendly insecticides
along with the inimical insects during its action
4) Different herbicides used for destroying weeds
can destroy the vegetation in the neighboring
areas also.
35. 5) Repeated use ofpesticides may produce
immunity or resistance in insects. Resistance has
been observed in houseflies, mosquitoes etc.
6) Effect
on human health ;- Pesticides cause
several harmful effects in human body. Pesticides
are proved to be lethal if their intake exceed a
maximum limit.
36. Sudden death can occur if we eat food
contaminated with pesticides. Long term intake of
small doses may lead to carcinogenic effect.
Pesticide also effect reproductive disorders such as
impotency. Studies conducted shows that the
presence of DDT and BHC in human milk .
Infant mortality have also been reported from
areas where high levels of DDT were found in
breast milk.
37. Pheromones:-
Pheromones are chemicals secreted by
female insects to attract the male.
By using synthetic pheromones,the males
of pests can be attracted ,trapped and
killed.
Tobacco caterpillar which is a serious pest
can be trapped using pheromones.
