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Neem (Azadirachta indiaca A.Juss) a native of Indian
sub-continent grows wildly and thrives under extremities of
climatic and soil conditions. All the parts of neem tree have
bio-active principles and these have found use in agriculture,public
health,medicines,toiletries,cosmetics and livestock production
and health. Among different plant parts , seed-kernel is the
richest source of bioactive materials. The seed kernel contains
40-50 % oil and 60-50 % cake.
The bitterness of neem is due to the presence of limonoids (triterpenoids
) .Out of over 300 limonoids occurring in Meliaceae family,
one third is accounted by neem and chinabeny (Melia azedarach)
alone. Neem bitter principles can be conveniently classified
under eight groups: promeliacins,limonoids with a modified side
chain ( e.g. y -hydroxy butenolides ), azadirone and its derivatives,
gedunin and its derivatives, vilasinin type compounds and those
belonging to three c-seco-meliacins-nimbin,salanin and azadirachtin.
These can be extracted from neem seed kernel.
Neem also contains non-isoprenoid constituents like polyphenolics,
carbohydrates, proteins and sulphurous compounds.
Neem by-products have application in agriculture especially
in increasing N-Use Efficiency and insect-pest, diseases and
nematode management.
Nitrification Inhibitor:
The neem extractives suppress activities of nitrifying bacteria
(Nitrosomonas and Nitrobacter) and thereby the rate
of nitrification which reduces loss of nitrogen through leaching
as nitrate and conserve NH4-N by reducing volatilization.
Insect Pest Management:
All parts of Neem tree are biologically active.The seed kernel
extract and pure compounds isolated from seeds have shown diverse
biological effects against several pests.These include the repellent,feeding
and oviposition deterrent, ovicidal, insect growth regulatory
(IGR ) and sterilant effects.
Management
of Plant Diseases:
Among the many plant species , Neem has been reported to possess
anti-fungal, anti-bacterial and anti-viral properties.
The growth of test fungi, Fusarium oxyporiyum F.Sp.,
Rhizoctonia solani, Sclerotium rolfsi was inhibited
in a medium containing extracts of neem leaf, trunk bark, fruit
pulp and neem oil. Oil treated seeds sown in a soil infested
with pathogens produced disease free seedlings.Nimbidin and
Nimbin obtained from neem oil showed very good inhibition of
several viruses
Nematicide:
Neem Cake, among different derivatives of neem, has shown to
be the most useful neem based agroindustrial by-product which
has no use other than a manure. However, besides manure it gives
excellent control of plant parasitic nematodes.
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