Neem is a stout tree with a rather short stem. They are native to India and other southeastern countries. A Neem tree generally grows up to 12-15 meters. They are best known for their medicinal properties. Neem tree is one of the richest reserves of secondary metabolites, mainly tetranortriterpenoids (limonoids), which are known to be responsible for insecticidal and wide pharmaceutical activities. The mature seed kernel and fruit were found to contain the highest amount of limonoids.
Neem oil is a vegetable oil pressed from the fruits and seeds of the Neem tree. It is perhaps the most important of the commercially available products of Neem. The oil is generally light to dark brown, bitter and has a rather strong odor. It comprises of mainly triglycerides and large amounts of triterpenoids compounds, which are responsible for the bitter taste. It is hydrophobic in nature and in order to emulsify it in water for application purposes, it must be formulated with appropriate surfactants. Neem oil also contains steroids (campesterol, beta-sitosterol, and stigmasterol) and a plethora of triterpenoids like azadirachtin, nimbin, picrin, and sialin. of which Azadirachtin is the most well-known and studied. The Azadirachtin content of Neem Oil varies from 300ppm to over 2000ppm depending on the quality of the neem seeds crushed. The method of processing is likely to affect the composition of the oil, since the methods used, such as pressing (expelling) or solvent extraction are unlikely to remove exactly the same mix of components in the same proportions. The Neem oil yield that can be obtained from neem seed kernels varies also widely in literature and varies from 25% to 45%.
The oil can be obtained through pressing (crushing) of the seed kernel both through cold pressing and through a process incorporating temperature controls. Neem seed oil can also be obtained by solvent extraction of the neem seed, fruit, oilcake or kernel. Using hexane this solvent-extracted oil is of a lower quality as compared to the cold pressed oil and is mostly used for soap manufacturing.
Before the oil can be taken out of the oilseed, the seeds are first ground up into a paste. Next, those ground up seeds are washed or purged with a solvent (also known as a petroleum distillate) such as hexane, to release the fat in the seed. To remove that solvent from the oil, it is “flashed off” through heat in a sealed chamber. Then the oil/solvent blend is heated to approximately 212˚ F, distilling off the solvent and theoretically leaving virtually no detectable levels in the oil if the proper techniques have been applied. However, microscopic portions of up to 25 parts per million (25 ppm) of hexane can theoretically remain in the meal, which has been a point of high debate in the natural food industry. Finally, that oil is then subject to the refining process, also known as “RBD” or Refined, Bleached & Deodorized in the industry. Solvent expelling gets 97-99% of the oil out of the seed.
Expelled pressing uses a press to physically squeeze the oil out of the seed, rather than use chemicals. With this method, no solvents are used in the process, and therefore don’t have the chance of having any hexane residue left over. Expeller pressing gets 87-95% of the oil out of the seed, so there is some oil still left over after pressing (though some claim as little as 65% is removed, so this is debated). Therefore, this option is not the cheapest, which can make this oil more expensive than the solvent expelled standard.
Cold pressed seed oils must be produced below 122˚ F and should only apply to fully unrefined oils that are not heated later during the refining process. The cold pressing process typically removes the least amount from the oil from the seed, making it the least efficient and the most expensive process available.
Formulations made of Neem oil also find wide usage as a bio-pesticide for organic farming, as it repels a wide variety of pests including the mealy bug, beet armyworm, aphids, the cabbage worm, nematodes and the Japanese beetle. Neem Oil is non-toxic to mammals and birds as well as many beneficial insects such as honeybees and lady bugs. Neem oil also controls black spot, powdery mildew, anthracnose and rust.
Neem seeds that have been crushed to produce oil do not go to waste. When dried, the resultant ‘cake’ contains nutrients that work as an organic pesticide and fertilizer that provides nourishment for soil.
Since early times neem is being used as a natural fertilizer in India. It had become very popular due to its dual impact of soil enhancer as well as pest-repellent. The cakes, as well as neem leaves, are used to fertilize the soil and to improve soil quality.
|Composition of Neem Cake|
|(N)||Nitrogen||(2.0% to 5.0%)|
|(P)||Phosphorus||(0.5% to 1.0%)|
|(K)||Potassium||(1.0% to 2.0%)|
|(Ca)||Calcium||(0.5% to 3.0%)|
|(Zn)||Zinc||(15 ppm to 60 ppm)|
|(Cu)||Copper||(4 ppm to 20 ppm)|
|(S)||Sulphur||(0.2% to 3.0%)|
|(Mg)||Magnesium||(0.3% to 1.0%)|
|(Fe)||Iron||(500 ppm to 1200 ppm)|
|(Mn)||Manganese||(20 ppm to 60 ppm)|
Neem cake can help retain water for the soil and improve its porosity as well as protects the roots from plagues and illnesses. Neem cake inputs more nitrogen, phosphorous, potassium, calcium and magnesium than common manure, making it ideal food for micro-organisms. Neem strengthens the organic content in the soil by reducing its alkalinity and producing organic acids on decomposition. Being completely natural, neem is compatible with soil microbes, nurtures healthy bacteria and ensures stronger texture, higher water holding capacity and aeration in the soil, all contributing towards better root development.
Neem makes the soil more fertile due to an ingredient that blocks soil bacteria from converting nitrogenous compounds into nitrogen gas. As a nitrification inhibitor, neem prolongs the availability of nitrogen to both short duration and long duration crops. Neem seed cakes can be mixed with urea or any other fertilizers (which have nitrogen). It will increase their efficiency by reducing their nitrogen releasing rate. So the fertilizers remain in the soil for much longer..
When mixed with soil it produces organic acids. So it reduces the alkalinity of the soil. Neem oil cakes improve the appearances of fruits and vegetables. It also strengthens roots, and grows the foliage. It works very well when mixed with compost or other organic fertilizers. Applying neem with nitrogenous fertilizers can slow down the conversion process. This increases the efficiency of the soil. In India, it is extensively used in cash crops like turmeric, sugarcane, banana etc. In growing flowers and vegetables, neem oil cakes are a good alternative to chemical fertilizers.
Neem seed cakes are very useful in controlling nematode population. It is also effective against many soil pathogens. Neem seeds and cakes contain nortriterpenoids and isoprenoids, which are nematicidal in nature.