What is Neem?
The Neem Tree
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.
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
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.