FERTILISER:
Materials commonly used for maintaining and improving soil fertility is known as Fertiliser.Manure and biofertilisers are examples of fertilisers.
MANURE:
Manures are the organic matter that increases the fertility of soil.They supply practically all the nutrient element acquired by plants especially the nitrogen contain and thus enhanced the crop productivity.
TYPES OF MANURE:
a)GREEN MANURE:
The practise of growing,plugging and mixing of green crops especially leguminous plant in the soil to increase the soil fertility is known as green manure.
ADVANTAGES:
i)Green manure helps in the fixation of atmospheric nitrogen to nitrate.
ii)Green manure helps to increase the fertility of soil.
iii)They protect the soil from erosion and leaching.
iv)They are the cheapest source of manure and easily available.
v)Provide organic substance and all the essential nutrients.
vi)They increase the yield of crops by 30% to 50%.
Some common examples of leguminous crops generally used in manuring are:
i)Crotalaria juncea(Sun hemp) ii)Vigna Sinensis(cow pea) iii)Trifolius alexendrinum iv)Lens esculenta
b)FARMYARD MANURE:
It consists of mixture of cattle dungs and crop residue.Cattle dung should be properly stored in a pit and surface is plastered with mud.Such materials become ready for manuring only after 2-3 months.
c)COMPOSITE OR ORGANIC MANURE:
Organic manure consists of rotten vegetable,animal refuse,farm weeds and other substancs .These are commonly used only after decomposition.
BIOFERTILISER:
Biofertilisers are organisms which can bring about enrichment of soil.The main source of biofertilizers are bacteria,fungi and cynobacteria.
a)RHIZOBIUM AS BIOFERTILISER:
It is well known that Rhizobium produces nodules in the roots of leguminous plants and fixes atmospheric nitrogen.Rhizobium culture develop in lab and are now being used for inoculation seeds of legume to make better nitrogen fixation and yields.More than 20% increase in the yield has been achieve in pulses like gram,lentils,beans etc.Yields of subsequent crops like wheat,rice are also increased.This benefit is due to the residual nitrate left in field after removal oof leguminous crops.
b)FREE LIVING NITROGEN FIXING BACTERIA OR AZOTOBACTER:
Fixation of nitrogen by free living micro organisms is termed as non symbiotic nitrogen fixation.Example:Azotobacter,Azomonas,Clostridium and Chlorobium are aerobic nitrogen fixing bacteria.Out of these Azotobacter is used for non leguminous crops.It is gram negative,aerobic,free living bacillus which may be motile.It is found in well aerated,neutral or slightly alkaline soil.Azotobacter can fix nitrogen under aerobic condition if the surrounding medium lack nitrogen.it is generally used before sowing the seed.Seeds are mixed with slurry of Azotobacter solution for 10 to 30 minutes and are transplanted immediately.
A varieties of crops are benifitted by Azotobacter biofertilizer and 20-30% increase in the yields of non leguminosae crop like cereal,oil seed,vegetables,plants etc,Not only increase in the yields of crops,the treatment of Azotobacter also increase in the germination percentage of crop.
c)CYONOBACTER AS BIOFERTILIZER:
Stagnant water in a paddy field enable growth of cyanobacteria.The cyanobacteria like Anabaena,Nostoc,Syctonema etc possess the ability to fix nitrogen.Cyano Bacteria as biofertilizer becomes active in the stagnant water of paddy.Incourse of time,water is covered with the scum of cyanobacteria along with nitrates.Cyanobacteria release vitamin C,Vitamin B12 and Auxin in surrounding water.
d)ANABAENA IN AZOLLA LEAF:
Azolla is aquatic fern that grows as an free floating hydrophyte.Due to very rapid and repeated vegetative propagation a carpet of Azolla plants are formed on the surface of water.Air space in the leaf of Azolla plants are occupied by cyanobacteria i.e Anabaena.Anabaena multiply and remain their till the decay of Azolla leaf.They shows mutualistic relationship.Anabaena fixes nitrogen from air into nitrogenous compound and Azolla give shelter to Anabaena; and they are release in water only after the decomposition of leaf.Thus there is appreciable increase in the yield of rice by the use of Azolla.
e)FUNGUS AS BIOFERTILIZER(MYCORRHYZAE):
Association of fungus with the roots of seeds of some plants is known as Mycorrhiza.It converts marginal land into fertile soil.It reduces fertilizer dependency of soil.It is of two types:
i)ECTOMYCORRHYZAE:
If the fungus is present outside the roots of oak,pine ,peach etc then it is Ectomycorrhizae.It absorbs and stores nitrogen,potassium,calcium in fungus mantle.It produces hybrid vigour.
ii)ENDOMYCORRHYZAE:
If fungus are present with the cell of cortex then it is known as Endomycorhyzae.The fungal hyphae penetrating the cells of cortex is Vesicular Abuscular Mycorrhyzae(VAM).
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