FERTILIZERS & INSECTICIDES

By SAHEED .V.K

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.

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.

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 definite 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, 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.

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. 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.

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 for 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 micro-flora and in turn the soil health in general.

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.

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 available1.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

PESTICIDES

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.

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.

Insecticides:-

Chemicals used to kill the insects are called insecticides. Insecticides are further classified into Stomach poisons, contact poison and fumigants .

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

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 fungi or eradicate fungal diseases of plants.

Eg: Lime, sulphur, formalin etc

Rodenticides:-

These are chemicals used to kill rats and mice which destroy crops and spread deseases.

Eg: Sodium fluoroacetate, 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 for 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 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.

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.

5) Repeated use of pesticides 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.

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.

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.

THE END