In view of the growing consciousness about environmental concerns arising from the use of agricultural chemicals, emphasis has been given to use organic input. India is endowed with various types of naturally available organic forms of nutrients in different parts of the country.
These include green manure, crop residues, farmyard manure, biogas slurry, animal and human excreta, compost, vermicompost, biofertilisers and many other indigenous nutrient management practices.
The area under green manure like sesbania (Dhaincha), Sunhemp, Cowpea etc. in India is roughly 22 lakhs ha and these contribute 60-200 kg N/ha in about 45-60 days. It is estimated that 1000 million tonnes of animal dung is produced in India annually, which yields about 500 million tonnes farm manure, which is excellent resource of plant nutrient.
An application of 10 tonnes well rotten FYM/ha can add 50-60 kg N, 15-20 kg P205 and 50-60 kg K20. Similarly 300 million tonnes crop residues, 285 million tonnes rural compost, 14 million tons city refuse, 28 million tonnes biogas slurry available in the country may be utilized widely as plant nutrient resources.
ADVERTISEMENTS:
All these sources contain, on an average, 0.5-2.0 per cent N, 0.2-1.0 per cent P205 , 0.5-1.5per cent K20. Apart from sources, biofertilisers containing the preparation of microorganisms like Rhizobium, Azotobacter, Azospirillum, Blue-green algae, Azolla may contribute 40-60 kg N/ha and P-solubilisers may add 20-30 kg P205 /ha. Currently 10000 MT of biofertilisers are being used in the country.
In recent times, vermicompost with the technology of earthworm rearing is being explored as another excellent source of plant nutrient and large numbers of units have been established in different parts of the country for its production and distribution.
Besides these sources, and other nutrient sources are oil cake, agro-industry wastes, biodynamic preparations, which are important components of organic nutrients.
The organic system includes cultural methods like crop rotation, selection of cultivation, use of natural enemies including insects (e.g., Dactylopius tomentosus for controlling prickly pear weed), and fungal organism (e.g., Alternaria eichhrinata, Collectotrichum gloesporiodes etc.) The uses of all these bio-control agents are encouraging.