Castor is an important industrial oilseed crop. Castor finds a place of prestige in the cropping systems of dry-land agriculture in semi-arid zones of India, because of its deep root system, drought hardiness, and quick growth. India occupies the second prestigious position in worlds castor market after Brazil. India also exports substantial part of its total castor produce to earn foreign exchange.Castor oil finds a number of uses for domestic, medicinal and industrial purposes. Castor oil contains a very high percentage (approximately 85 per cent) of hydroxy fatty acid known as recinoleic acid. Recinoleic acid can be treated by dehydration. This dehydrated castor oil is in demand for paints and varnishes because of its non-yellowing quality.Castor oil is used as a lubricant in all moving parts of machinery, and for internal combustion engines especially those used in airplanes.
It is also used as an illuminant, giving a bright and steady flame and burning much longer than any other vegetable oil. Hydrogenated castor oil is used in polishes, ointments, waxes, printing inks, cosmetic, hair dressings, soaps and disinfectants. Castor oil is also used as a purgative. In dyeing industries, it is used for the preparation of `Turkey red.
Castor oil is used in many veterinary uses. It is used externally as an emollient. It is also used as a soothing medium when dropped into the eyes of animals after removal of foreign bodies.
The castor oil cake is a valuable manure, but owing to the presence of the poison `ricin it is unfit for cattle feed. It contains about 5.5 per cent nitrogen, 1.8-1.9 per cent phosphorus and 1.1 per cent potash.
Area of Cultivation
The castor plant grows throughout India up to an elevation of 2500 metres. Andhra Pradesh, Gujarat, Orissa and Karnataka are the important castor growing states.
Season
Castor requires a moderately high temperature 20-27°C with low humidity throughout the growing season. It grows best in areas where there are clear warm sunny days. Prolonged cloudy weather with high temperature at the time of flowering results in poor seed set. High temperature above 41°C at flowering time even for a short period results in blasting of flowers and poor seed set. The plant is considered to be very resistant to drought but even then about 80-1000 mm evenly distributed rainfall in required for optimum growth. Heavy rainfall at flowering reduces the yield. Castor plant is very susceptible to frost.
Soil
Castor can be raised practically on any type of soil, but as with a number of other plants, a well drained loam will produce the optimum yield. Very heavy clays and marshy conditions are unfavourable for proper growth. The cultivation of castor should, however, be confined to the upland areas as this crop is highly susceptible to water logged conditions. The crop can also not tolerate alkalinity of soil but can withstand slight to moderate acidity of soil.