“The all pervasive use of synthetics in every walk of life, be it agriculture, clothing, preservation or health-care is now paving way for a search for eco-friendly products. All communities, internationally, are today inclined to trust and rely more on green technology than ever before since the advent of modern science. The era of dependency on synthetic chemicals of the early and middle twentieth century prompted synthesis of newer chemicals as a panacea for all diseases and ailments. The conservative attitude of some societies, which depended on natural products in preference to the synthetic, was often credited to inertia or backwardness.
Happily, modern societies today, finding themselves confounded in the web of their creation, are wiling to revert to nature for remedies” (Govt. of India, 1996). It is in this that neem has staged a comeback and promises to hold centre stage in the coming years.
Neem is extremely beneficial to save the environment from pollution; since its in-florescence is purifying ‘with its feathery crests tossing fifty feet into the sky’ neem is a veritable “Kalpataru” for giving healthy environs. Like other trees, it exhales out oxygen and keeps the oxygen level in the atmosphere balanced.
Like other trees, it also brings other environmental benefits such as flood control, reduced soil erosion and less salination. Neem can avert environmental crisis in India and other tropical countries as it can be successfully used for rehabilitation of degraded ecosystems and waste lands. Neem is highly recommended for reforestation of semi-arid regions in India and tropics of the sub-Saharan region, Asia and Central America. Neem is extremely useful in urban forestry because it has remarkable ability to withstand air and water pollution as well as heat. Neem also helps in restoring and maintaining soil fertility which makes it highly suitable in agro-forestry.
Neem is a natural resource to keep environment clean. In villages and cities as well as on farms, it is useful as a windbreak. As a source of shade, it is excellent for parks, roadsides etc. Because of its so many qualities, it is a common practice in rural India to have a neem of tree within the compounds of most of the houses. Neem is also a regarded as a valuable forestry species in India.
Neem has powerful pest controlling activities and medicinal properties. More importantly, pesticides made from neem are much safer compared to synthetic pesticides. The side-effects of the synthetic pesticides are often not less serious than the problems themselves. They cause environmental contamination and are a great risk of human health. As a consequence, there has been an intense search for safer pesticides.
Pesticides made from neem are products of natural plant origin. They are biodegradable and non-toxic. Neem products produce no ill-effects to humans and animals; they have no residual effect on agriculture produce. For these reasons Neem is considered as the best substitute to hazardous pesticides.
With the current thrust on sustainable agriculture and organic farming, the use of botanical products as pesticides has acquired greater significance. Neem is a highly suitable candidate for environment-friendly, safe agriculture development. Azadirachtin can be used in agriculture and public health as an eco-friendly chemical. Use of neem products for plant protection will reduce the demand for chemical pesticides and thereby reduce the environmental load of these synthetic pesticides.
Synthetic pesticides are also a major source of health problems. With the use of bio-peticides, farmers can avoid health hazards which frequently occur both in developed and developing countries.
ENVIRONMENTAL SERVICE RENDERED BY NEEM
Neem in Indian culture has been ranked higher than ‘Kalpavriksha‘, the mythological wish-fulfilling tree. In ‘Sharh-e-Mufridat Al-Qanoon, neem has been named as ‘Shajar-e-Mubarak‘, ‘the blessed tree’, because of its highly beneficial properties. Although scientific studies are wanting, neem is reputed to purify air and the environment of noxious elements. Its shade not only cools but prevents the occurrence of many diseases.
During hot summer months in northern parts of the Indian subcontinent, the temperature under the neem tree is ~10° C less than the surrounding temperature; 10 air conditioners operated together may not do the job as efficiently and economically as a full grown neem. Restoration of the health of degraded soils and ultimate use of such reclaimed wastelands lands through neem is another example of its value as an environmental panacea.
About a decade ago, some 50,000 neem trees were planted over 10 kms on the Plains of Arafat to provide shade for Muslim pilgrims during hajj. The neem plantation has had a marked impact on the area’s microclimate, microflora, microfauna, sand soil properties, and when full grown could provide shade to 2 million pilgrims (Ahmed 1995). It is an ancient belief that neem growing inside the house can keep the surrounding air clean of impurities and thereby control environmental pollution. Also, hanging neem twigs on the door of a house is said to offer protection against pollution and disease.
The tree is not only beautiful to look at, providing grandeur and serenity, but also serves as a refugia to many beneficial organisms, bats, birds, honey bees, spiders, etc. Honey-combs established on the neem tree are singularly free from the galleria wax moth infestation. Many species of birds and fruit-eating bats subsist on the sweet flesh of ripe fruits, while certain rodents selectively feed on the kernel, confirming neem’s safety to warm-blooded animals. The litter of falling leaves improves soil fertility and the organic content. Presently, little is known about the mycorrhizal associations between neem and bacterial and fungal endophytes, but the tree seems to be a living microcosm.
The evergreen, perennial tree can survive up to from 200 to 300 years, if not cut down. Even a highly conservative estimate of the ‘environmental service’ rendered by the tree @ US $ 10 per month, would give an astonishing value of US $ 24,000 to 36,000 in its life time. Other economic uses of neem and the benefits derived, such as biomass production, timber, seed and honey are more tangible and quantifiable.
NEEM IN REFORESTATION AND AGRO-FORESTRY
Neem is a very valuable forestry species in India and Africa and is also becoming popular in Tropical America, the middle-east countries and in Australia. Being a hardy, multipurpose tree, it is ideal for reforestation programs and for rehabilitating degraded, semiarid and arid lands. During a severe drought in Tamil Nadu State in June-July 1987, it was witnessed that neem grew luxuriantly, while other vegetation dried up.
Neem is useful as windbreaks and in areas of low rainfall and high wind speed. In the Majjia Valley in Niger, over 500 km of windbreaks comprised of double rows of neem trees have been planted to protect millet crops which resulted in a 20% increase in grain yield (Benge 1989). Neem, windbreaks on a smaller scale have also been grown along sisal plantations in coastal Kenya. Large scale planting of neem has been initiated in the Kwimba Afforestation Scheme in Tanzania.
In countries from Somalia to Mauritiania, neem has been used for halting the spread of the Sahara desert. Also, neem is a preferred tree along avenues, in markets, and near homesteads because of the shade it provides. However, neem is best planted in mixed stands. It was probably no coincidence that Emperor Ashoka, the great ruler of ancient India, in the 3rd century BC, commanded that the neem be planted along the royal highway and roads along with other perennials-tamarind, Tamarindus indica and mahua, Madhuca longifolia var. latifolia. Neem has all the good characters for various social forestry programs.
Neem is an excellent tree for silvipastoral system involving production of forage grasses and legumes. But according to some reports (Radwanski and Wickens 1981), neem cannot be grown among agricultural crops due to its aggressive habit. Others say that neem can be planted in combination with fruit cultures and crops such as sesame, cotton, hemp, peanuts, beans, sorghum, cassava, etc., particularly when neem trees are still young. The neem tree can be lopped to reduce shading and to provide fodder and mulch. Recent advances in tissue culture and biotechnology should make it possible to select neem phenotypes with desirable height and stature for use in intercropping and various agro-forestry systems. The alleloopathic effects of neem on crops, if any, need to be investigated.
BIOMASS PRODUCTION AND UTILIZATION
Full grown neem trees yield between 10 to 100 tons of dried biomass/ha, depending on rainfall, site characteristics, spacing, ecotype or genotype. Leaves comprise about 50% of the biomass; fruits and wood constitute one-quarter each. Improved management of neem stands can yield harvests of about 12.5 cubic meter (40 tons) of high quality solid wood/ha.
Neem wood is hard and relatively heavy and religious icons in some parts of India. The wood seasons well, except for end splitting. Being durable and termite resistant, neem wood is used in making fence posts, poles for house construction, furniture etc. There is growing market in some European countries for light-colored neem wood for making household furniture (H. Schmutterer, personal communication). Pole wood is especially important in developing countries; the tree’s ability to resprout after cutting and to regrow its canopy after pollarding makes it highly suited to pole production (National Research Council 1992). Neem grows fast and is a good source of firewood and fuels; the charcoal has high calorific value.