FERTILIZERS & INSECTICIDES
By SAHE SAHEED ED .V.K
FERTILIZERS Substances which are added to the soil to increase its fertility are called Fertilizers. Fert ilizers. 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 a s natural fertilizers. Since the demand for fertilizers cannot be met by natural fertilizers alone, many compounds compo unds are manufactured manufact ured to provide nitrogen, potassium and phosphorous to plants. These chemicals are known as artificial or chemical fertilizers.
FERTILIZERS Substances which are added to the soil to increase its fertility are called Fertilizers. Fert ilizers. 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 a s natural fertilizers. Since the demand for fertilizers cannot be met by natural fertilizers alone, many compounds compo unds are manufactured manufact ured to provide nitrogen, potassium and phosphorous to plants. These chemicals are known as artificial or chemical fertilizers.
Important natural inorganic fertilizers are potassium salts and rock phosphate. The important source of potassium are wood ash and waste waste materials of sugar beet crop.
Potassium salts increase the quantity of crops and Potassium enable the plants to resist the diseases. Other Othe r naturally natur ally occurring potassium salts are niter or saltpeter(Potassium nitrate) carnalities ( containing potassium chloride)
Rock phosphate is a naturally occurring phosphorous fertilizer.
Artificial
inorganic fertilizers (Synthetic fertilizers)
Nitrogenous fertilizers: Important nitrogenous fertilizers are 1) Ammonium sulphate 2 ) Ammonium phosphate 3 ) Calcium Cyanamid 4 ) Urea
Phosphatic fertilizers:Important phosphatic fertilizers are
1) Super phosphate of lime ( Calcium super phosphate) 2) Triple super phosphate 3) Ammonium superphosphate
Mixed
fertilizers:-
A fertilizer which contains more than one plant nutrients is called mixed fertilizer.
Mixed
fertilizer Containing nitrogenous, phosphatic and potash fertilizers in def inite proportions. Such fertilizers are called NPK fertilizers
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, P 2O5, and K2O respectively .
Eg: NPK Vlue of 10:5:20 for a mixed fertilizer means that the particular fertilizer contains 10% nitrogen, 5% P 2O5 and 20% K2O.
Impact of excessive use of fertilizers on environment
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.
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.
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.
Phosphate based fertilizers are also used in addition to nitrogen based fertilizers. Unf ortunately, 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 f or the additional phosphorus that fertilizers add to soils.
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.
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.
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 f or people
BIO FERTILIZERS:
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 microflora and in turn the soil health in general.
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 f ossil f uel (coal+ petroleum). With
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.
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.
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.
Types of biofertilizers available 1.For Nitrogen Rhizobium f or legume crops. Azotobacter/Azospirillum f or non legume crops. Acetobacter f or sugarcane only. Blue Green Algae (BGA) and Azolla f or low land paddy. 2.For Phosphorous Phosphatika f or all crops to be applied with Rhizobium, Azotobacter, Azospirillum and Acetobacter 3.For enriched compost Cellulolytic f ungal culture Phosphotika and Azotobacter culture
PESTICIDES
Pesticides are chemical substances used to kill insects, f ungi, rodents,weeds or other living things which are harmf ul to plants, animals or f oodstuff s. Pesticides f unction as poisons f or the important biological process of insects, f ungi etc which lead to the death of these organisms.
Classification
of pesticides
Depending upon the purpose for which the pesticides are used, they are classified as follows. i) insecticides ii) herbicide iii) fungicides iv) rodenticides
v) algaecide vi) molluscicides vii) miticides viii) nematocides.
Pesticides may be organic, inorganic, or compounds obtained from natural products.
Insecticides:Chemicals used to kill the insects are called insecticides. Insecticides are f urther classif ied into Stomach poisons, contact poison and f umigants .
Stomach poisons are absorbed through the digestive system of the insects. These are effective against insets like caterpillar. Eg; Acid lead arsenate , cryolite ,sodium f luoride. 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
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 ).
Fungicides:Fungicides are are chemicals which are used to prevent the growth of f ungi or eradicate f ungal diseases of plants.
Eg: Lime, sulphur, f ormalin etc
Rodenticides:These are chemicals used to kill rats and mice which destroy crops and spread deseases.
Eg: Sodium f luoroacetate, Zinc phosphide etc
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
Miticides:-
Chemicals used to destroy mites are called miticides . eg: organo phosphates. Nematocides:These are chemicals used f or the distruction of nematodes like round worms, thread worms etc . eg: dimethoate
Environmental impact of pesticides
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 f ishes. 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.
2) Certain pesticides such as DDT, BHC etc persisted in the environment accumulated in blood,milk and f at 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 f or destroying weeds
can destroy the vegetation in the neighboring areas also.
5) Repeated
use of pesticides may produce immunity or resistance in insects. Resistance has been observed in housef lies, mosquitoes etc. 6) Effect
on human health ;- Pesticides cause several harmf ul effects in human body. Pesticides are proved to be lethal if their intake exceed a maximum limit.
Sudden death can occur if we eat f ood 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 .
Inf ant mortality have also been reported from areas where high levels of DDT were f ound in breast milk.
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.
