FERTILIZERS Substances which are added to the soil to increase itsfertility are called Fertilizers.Many natural substance like leaves, cow dung, bone mealcompost etc are used to make up the deficiency ofnitrogen , phosphorus and potassium in soils. Thesesubstance are known as natural fertilizers.Since the demand for fertilizers cannot be met by naturalfertilizers alone, many compounds are manufactured toprovide nitrogen, potassium and phosphorous to plants.These chemicals are known as artificial or chemicalfertilizers.
Important natural inorganic fertilizers are potassiumsalts and rock phosphate. The important source ofpotassium are wood ash and waste materials of sugarbeet crop.Potassium salts increase the quantity of crops andenable the plants to resist the diseases. Othernaturally occurring potassium salts are niter orsaltpeter(Potassium nitrate) carnalities ( containingpotassium chloride)Rock phosphate is a naturally occurring phosphorousfertilizer.
Phosphatic fertilizers:-Important phosphatic fertilizers are1) Super phosphate of lime ( Calcium superphosphate)2) Triple super phosphate3) Ammonium superphosphate
Mixed fertilizers:-A fertilizer which contains more than one plantnutrients is called mixed fertilizer.Mixed fertilizer Containing nitrogenous,phosphatic and potash fertilizers in definiteproportions.Such fertilizers are called NPK fertilizers
NPK Value:-The efficiency of a fertilizer is expressed in terms of NPKValue. N,P,K stands for Nitrogen, Phosphorous andPotassium.It expresses the nitrogen, phosphorous and potassiumcontents in terms of elementary nitrogen, P2O5, and K2Orespectively .Eg: NPK Vlue of 10:5:20 for a mixed fertilizer means that theparticular fertilizer contains 10% nitrogen, 5% P2O5 and 20%K2O.
Impact of excessive use offertilizers on environment
The increased use of fertilizers to expandfood supplies have come at a large cost to ourenvironment.Modern agricultural techniques are typicallywasteful in their use of fertilizers.
Often, many farmers add large amounts offertilizer or manure at the time of sewing inorder to cover and protect the young plants.This technique is inefficient, since the youngplants are unable to absorb most of thenitrogen.Therefore, much of the nitrogen is lost to theenvironment in a number of ways.
For example, the nitrate directly leachingoff into the environment as water runs off ofthe field is a leading cause.Once the nitrogen is introduced into theground system, the ammonium ions, whichare normally in equilibrium with ammoniain the soil, are disturbed. This action causesa disruption in the pH of the soil, whichaffects plant growth.
Phosphate based fertilizers are also used inaddition to nitrogen based fertilizers.Unfortunately, as with nitrogen based fertilizers,there are negative environmental consequences.The increasing use of phosphate fertilizers has ledto the accumulation of phosphorus in soils. Thiscauses problems because the means by whichphosphorus is immobilized cannot accommodatefor the additional phosphorus that fertilizers addto soils.
Consequently, high concentrations ofphosphorus flow away with agriculturalrunoff.The toxic effects of phosphorus becomenoticeable when agricultural runoff isdeposited in lakes , streams and other watersources because excessive amount ofphosphorus leads to eutrophication.
Eutrophication, a natural process by which lakes,streams and some estuaries age, is sped up byactivities such as land clearing, production andapplication of fertilizers, agricultural runoff andrelease of human waste.The previously mentioned processes result in themobilization of nutrients such as nitrogen andphosphorus into aquatic systems.These nutrients disrupt aquatic systems byincreasing the growth of unwanted algae and aquaticweeds. As these organisms die they reduce theoxygen supply available for other organisms.
Without dissolved oxygen in the water, mostorganisms cannot survive. The depletion ofoxygen also promotes the conversion ofcompounds to their toxic form which maypotentially harm more organisms. If the fertilizers end up in drinking water,they can cause health problems for people
Biofertilizers are ready to use liveformulates of such beneficialmicroorganisms which on application toseed, root or soil mobilize the availability ofnutrients by their biological activity inparticular, and help build up the micro-flora and in turn the soil health in general.
With the introduction of green revolution technologiesthe modern agriculture is getting more and moredependent 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 excessiveand imbalanced use of these synthetic inputs. Thissituation has lead to identifying harmless inputs likebiofertilizers.Use of such natural products like biofertilizers in cropcultivation will help in safeguarding the soil health andalso 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 soilborne diseases.
Advantages of bio-fertilizers1.Cost effective.2.Suppliment to fertilizers.3.Eco-friendly (Friendly with nature).4.Reduces the costs towards fertilizers use, especiallyregarding 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 Acetobacter3.For enriched compost •Cellulolytic fungal culture •Phosphotika and Azotobacter culture
Pesticides are chemical substances used to killinsects, fungi, rodents,weeds or other livingthings which are harmful to plants, animals orfoodstuffs.Pesticides function as poisons for theimportant biological process of insects, fungietc which lead to the death of theseorganisms.
Classification of pesticidesDepending upon the purpose for which thepesticides are used, they are classified asfollows. i) insecticides v) algaecideii) herbicide vi) molluscicidesiii) fungicides vii) miticidesiv) rodenticides viii) nematocides. Pesticides may be organic, inorganic, or compounds obtained from natural products.
Insecticides:-Chemicals used to kill the insects arecalled insecticides. Insecticides arefurther classified into Stomach poisons,contact poison and fumigants .
Stomach poisons are absorbed through thedigestive system of the insects. These areeffective against insets like caterpillar. Eg; Acidlead arsenate , cryolite ,sodium fluoride.Contact poisons affects the insects on contact.eg:DDT,BHC,Dieldrin(Chlorinated hydrocarbon)melathion,parathion(Organo phosphatecompounds). Fumigents aregaseous chemicals which killsinsects by entering directly to the respiratorysystems. Eg: Hydrogen cyanide, naphthalene,nicotine
Herbicides:-Herbicides are used to destroy weeds (destroythe 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 areused to prevent the growth of fungi oreradicate fungal diseases of plants.Eg: Lime, sulphur, formalin etc
Rodenticides:-These are chemicals used to kill rats and micewhich destroy crops and spread deseases.Eg: Sodium fluoroacetate, Zinc phosphide etc
Algaecide:-These are chemicals added to water todestroy algae.Eg: copper sulphateMolluscicides:-These are chemicals used to destroymollusks like snails , slugs etceg: Copper sulphate, metaldehyde etc
Miticides:-Chemicals used to destroy mites are calledmiticides .eg: organo phosphates.Nematocides:-These are chemicals used for the distruction ofnematodes like round worms, thread wormsetc .eg: dimethoate
Environmental impact of pesticides
The excessive use of pesticides have created tremendous adverseeffects on environment1) Environmental pollution:- Pesticides drained to water bodies causes waterpollution . hence water in river, lakes and seas getspolluted which becomes hazardous to aquaticanimals like fishes.Pesticides may also washed down to ground waterwhich pollute drinking water. During the sprayingof pesticides it may reach in to atmosphere andpollute 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 animals3) Pesticides may kill the friendly insecticidesalong with the inimical insects during its action4) Different herbicides used for destroying weedscan destroy the vegetation in the neighboringareas also.
5) Repeated use ofpesticides may produceimmunity or resistance in insects. Resistance hasbeen observed in houseflies, mosquitoes etc.6) Effect on human health ;- Pesticides causeseveral harmful effects in human body. Pesticidesare proved to be lethal if their intake exceed amaximum limit.
Sudden death can occur if we eat foodcontaminated with pesticides. Long term intake ofsmall doses may lead to carcinogenic effect.Pesticide also effect reproductive disorders such asimpotency. Studies conducted shows that thepresence of DDT and BHC in human milk .Infant mortality have also been reported fromareas where high levels of DDT were found inbreast milk.
Pheromones:-Pheromones are chemicals secreted byfemale insects to attract the male.By using synthetic pheromones,the malesof pests can be attracted ,trapped andkilled.Tobacco caterpillar which is a serious pestcan be trapped using pheromones.