Castor Plant History & Overview
The castor plant has been known to man for ages. Castor beans have been found in ancient Egyptian tombs dating back to 4000 B.C. , and the oil was used thousands of years ago in wick lamps for lighting. To many people the castor plant is just an overgrown, undesirable weed and yet it produces one of nature’s finest natural oils.
Castor (Ricinus communis L.) is an important non-edible oilseed crop.It is cultivated around the world primarily because of the commercial importance of its oil. India is the world’s largest producer of castor seed and meets most of the global demand for castor oil, contributing over 60% of the entire global production.
The shiny seeds of castor plants have very beautiful and intricate designs. Like the fingerprints of humans, the beautiful designs on castor seeds exhibit infinite genetic variation, and no two seeds have the same design.
The seed pod is composed of three sections or carpels which split apart at maturity. Each section contains a single seed, and as the carpel dries and splits open, the seed is often ejected with considerable force.
Castor oil is extracted from the seeds by either pressing or solvent extraction.
Plant Description
Coarse perennial, 10–13 m tall in the tropics, with the stem 7.5–15 cm in diam., but usually behaves as an annual in the temperate regions 1–3 m tall; stems succulent, herbaceous, very variable in all aspects; leaves alternate, orbicular, palmately compound, 1–6 dm broad, with 6–11 toothed lobes, glabrous; flowers numerous in long inflorescences, with male flowers at the base and female flowers at the tips; petals absent in both sexes, sepals 3–5, greenish; stamens numerous, 5–10 mm long; ovary superior, 3-celled with a short style and 3 stigmas; fruit a globose capsule 2.5 cm in diameter, on an elongated pedicel, usually spiny, green turning brown on ripening, indehiscent in modern cultivars, usually containing 3 seeds; seeds ovoid, tick-like, shiny, 0.5–1.5 cm long, carunculate, vari-color with base color white, gray, brownish, yellow, brown, red, or black, with the outer pattern gray or brown to black, the pattern varying from fine to coarse, veined or finely dotted to large splotches, poisonous and allergenic, possibly fatel, from 1,000 to 11,000 per kg, commercial varieties having 2200 to 3200 per kg (Reed, 1976).
Plant Ecology
Ranging from Cool Temperate Moist to Wet through Tropical Desert to Wet Forest Life Zones, castorbean is reported to tolerate annual precipitation of 2.0 to 42.9 dm (mean of 68 cases = 12.7) annual temperature of 7.0 to 27.8°C (mean of 68 cases = 20.4) and pH of 4.5 to 8.3 (mean of 29 cases = 6.5). Grows best where temperatures are rather high throughout the season, but seed may fail to set if it is above 38°C for an extended period. Plant requires 140–180 day growing season and is readily killed by frost. Irrigated crops require 2–3.5 acre-feet of water to produce satisfactory yields. High humidity contributes to the development of diseases. Plants do best on fertile, well-drained soils which are neither alkaline nor saline; sandy and clayey loam being best.
Castor Cultivation
Castor is propagated entirely by seed treated to resist disease. Seeds retain their viability 2–3 years. After seedbed has been deeply cultivated, seed of the dwarf cvs in mechanized countries are planted 3.7–7.5 cm deep in rows 1 m apart; seeds about 25 cm apart in the rows; at rate of 15 kg/ha. For unmechanized societies which prefer larger cvs, seeds are planted 60 by 90 cm apart, 2–4 seeds per hole, and then thinned to one plant; this gives about 30,000 plants/ha. Cultivate shallowly until 0.6–0.9 m high. Irrigation is usual practice in the United States; in India castor is a dryland crop. Castor exhausts the soil quickly. In the United States 45–135 kg/ha of nitrogen is added in split applications. Leaves, stalks and seed hulls are disked into the field following harvest. In India 89 kg/ha of nitrogen gives the highest yields. Where phosphorus is deficient, 40–50 kg/ha of P2O5 is recommended. In Australia 200 kg/ha of superphosphate is applied. Furrow irrigation is preferred, but subirrigation reduces weed problems. Normally irrigation commences after plants have 6–8 leaves; overirrigation on heavy soils should be avoided; final irrigation should be 3–4 weeks before harvest. In the United States 1,500 to 2,000 cu m of water per hectare is applied during the growing season. In Brazil 2,400 cu m of water is applied during the 3 months between flowering and harvest, with about 400 cu m being applied at each irrigation at 15 day intervals. Seed may be planted by hand or with a corn planter with special plates, after the soil has become warm and out of danger of frost. Time varies with the locality; Illinois, early May; Venezuela, June–July; Australia, August–December; Morocco, March; Brazil (south), September–November; Brazil (north), January–March; India, July; Taiwan, August–September or April–May. For seed increase, castor should be planted on fallow land, and should not follow small grains or another castor crop. In India it is rotated with ragi, groundnuts, cotton, dryland chillies, tobacco or horsegram (Reed, 1976).
Harvesting
Non-mechanized societies prefer shattering cvs, as opposed to the non-dehiscent dwarf strains developed in the United States. Fruits are harvested when fully mature and the leaves are dry, in about 95–180 days depending on the cv. In tropics, harvest is from wild or native plants. Planting and harvesting may be done by hand methods or be completely mechanized. Harvesting should begin before rainy season in tropical regions, but in dry regions it is best to harvest when all fruits are mature. In India fruit is picked in November; in the United States harvesting begins in October. In the tropics most harvesting is by hand; the spikes are cut or broken off, the capsules stripped off into a wagon or sled, or into containers strapped on the workers. Unless the capsules are dry, they must be spread out to dry quickly. In India fruits are collected and spread in piles to dry in the sun until they blacken. In the United States drying may be accomplished by frost or by the use of defoliants; chemical defoliants are also used in Australia. In South Africa and Australia modified wheat headers are used for harvesting; in the United States more expensive harvesters are used which shake capsules from plants by jarring plants at their bases. Relative humidity of 45% or less is required for efficient operation with mechanical harvesters. Seed capsules shatter easily in most cvs. Some indehiscent varieties are threshed by ordinary grain thresher at 400–800 r.p.m. cylinder speed. After harvesting, seeds must be removed from the capsules or hulls, usually with hulling machines if capsules are dry. Percentage of seed to hull averages 65–75, depending upon the maturity of the seed at harvest. In India seeds are beaten out with sticks, winnowed and screened to remove hulls and trash. In South Africa, Brazil and the United States seed is decorticated with special castorbean decorticators. When small amounts of seed are involved, they may be decorticated on a rubbing board. An ordinary thresher is rarely suitable since the beater bar or peg drums break up the soft seeds. Castor oil is manufactured by running cleaned seed through the decorticating machines to remove the seed coat from the kernel; the more complete this operation the lighter the oil. Castor seeds cannot be ground or tempered as flaxseed or soybeans. Unbroken or uncrushed seeds should be gotten to the press. Preheating may make heavy viscous oil more mobile. Seed is put in ‘cage’ press, and number 1 oil is obtained, which needs little refining but has to be bleached. Oil remaining in the press-cake is extracted by solvent methods and is called number III oil, which contains impurities, and cannot be effectively refined. Castorbean oil can be stored 3–4 years without deterioration.
Yields & Economics
Average seed yields range from 900–1000 kg/ha under irrigation, and 300–400 kg/ha without adequate moisture. Some improved open-pollinated varieties in Brazil and the United States yield 1,300 kg/ha, with exceptional yields up to 5,000 kg/ha. Average Indian yields are 560 kg/ha. Oil content of seeds varies from 35 to 55%, suggesting potential oil yields of 200–2,750 kg/ha. In February 1982, the U.S. Bureau of Census noted “surprising” castor oil consumption. In the U.S. nearly 4,000 MT of the oil was used, an increase of ca 1,500 MT over January. In April of 1982, prices ranged from 42 to 72 cents per pound (92 to $1.58/kg) depending on quality and grade (CMR, April 26, 1982). During and since World War II, castor production increased in South America, Thailand and Haiti. In 1952, about 50,000 kg of castor oil was imported in the United States, mostly from India, Belgium, West Germany, Holland, Peru, Manchuria, China, Argentina, Mexico, Brazil and Paraguay; and 65,000,000 kg of seeds, mostly from Brazil, Ecuador, Thailand, India, Haiti and Ethiopia. World production was 723,000 MT on 1,285,000 kg, yielding 560 kg/ha. Wholesale prices for beans in 1969 from India was 15.2 cents/kg and from Europe 16.6 cents/kg. In 1971 prices from Brazil were $293/T. Prices vary: Italy 93.1 cents/kg producer price; Spain 66.6 cents/kg, export price; and the United States 85.3 cents/kg, import price. In 1970 more than 469,000 MT of oil was produced in the world, representing about 1% of the oil market. The 1980 projection was for 554,000 MT, which is a 4.2% increase.
Energy from Castor Crop
Gaydou et al. (1982) rank oilseeds more promising for energy in Malagasy than sugarcane and cassava. Castor was least promising of the four oilseeds, producing 1,200–2,000 liters oil/ha (equivalent to 11,300 to 18,906 kwh) compared to tung at 1,800–2,700 l, purging nut at 2,100–2,800 l, and oilpalm at 2,600–4,000 l/ha. They calculated ca 1,000 l ethanol for cassava and 2,500 for sugarcane. Yields of 5 MT seeds are reported. When the oil is expressed, the oil cake remaining amounts to 45–50% of production (Devendra and Raghavan, 1978). In some of the dwarf temperate trees (treated as annuals), the straw factor is not much more than one, but perennial tropical trees may have a standing biomass of 25 MT/ha or more. The hull residue is calculated at 0.25 times production. Hulls have about the same fertilizer value as fresh barnyard manure.
Castor Crop Pollination
Castor bean is both self- and cross-pollinated by wind, varying from 5–36% depending on the weather conditions. Pollen sheds readily between 26–29°C, with a relative humidity of 60%. For single cross hybrid seed production, strains giving a 1:1 ratio or pistillate and heterozygous monoecious plants are used, the latter being rogued 1–5 days before flowering begins. Three-way cross hybrids can also be used. For open pollinated types, roguing of all off-types is done after the last cultivation, and for pure seed production isolation necessity depends on the wind velocity. For hybrid and open pollinated types in the United States, stands are isolated 300–720 m, but in areas of less wind velocity, less distance may be sufficient.
Pests that are Harmful to Castor Plant
Several insects are pests. In India the Capsule borer (Dichocrocis punctiferalis) bores into young and ripening capsules; and the Castor semilooper (Achoea janata) are the worst pests. In Tanganyika damage by capsid and myrid bugs are a limiting factor causing immature fruit to drop. Green stinkbugs, leaf-hoppers, leaf-miners and grasshoppers are pests that feed on the leaves. Most insects may be controlled by insecticides. Because some of the varieties are quite tall, wind storms are a potential hazard to a crop.
The Producers
Because of its unlimited industrial applications, castor oil enjoys tremendous demand world-wide. It is cultivated in 30 different countries on commercial scale, of which India, China , Brazil , Russia , Thailand , Ethiopia and Philippines are the major castor growing countries, accounting for almost 90 percent of the world’s production. Historically, Brazil, China and India have been the key producing countries meeting global requirements. However, in early 90’s, Brazilian farmers moved away to more lucrative cash crops, and surge in domestic demand in China made them net importers, leaving India to meet the global demand.
Sowing Time
- Sowing of castor with onset of monsoon is found most beneficial in rained condition. However, sowing can be done up to first fortnight of August without reduction in yield under irrigated condition.
Cropping Season
- In India, which is a major producer of the castor crop, castor planting season is during July or August and harvested around December or January. The seedpods are dried, de-podded and brought to the market immediately after harvesting.
- Castor seeds arrivals start during November in the south of India, whereas in the north (in states such as Rajasthan and Gujarat), the castor seeds season starts from February. Based on this cycle, one can suitably schedule delivery cycles as well.
Price of Castor Seeds
- This is a difficult thing to comment on, since price variations and fluctuations are quite significant for this commodity.
Castor Seed Packaging
The normal packing is either 50 Kgs or 70 Kgs, and the products are usually packed in gunny bags (Gunny Bag Definition from Die.net)
Other Specifications for Castor Seeds
While there are no major specifications for castor seeds, one of the aspects usually considered is the location where the castor seed was grown and harvested.
Castor Plant Chemistry
Per 100 g, the leaves are reported to contain on a zero-moisture basis, 24.8 g protein, 5.4 g fat, 57.4 g total carbohydrate, 10.3 g fiber, 12.4 g ash, 2,670 mg Ca, and 460 mg P. The seed contains 5.1–5.6% moisture, 12.0–16.0% protein, 45.0–50.6% oil, 3.1–7.0 NFE, 23.1–27.2% CF, and 2.0–2.2% ash. Seeds are high in phosphorus, 90% in the phytic form. The castor oil consists principally of ricinoleic acid with only small amounts of dihydroxystearic, linoleic, oleic, and stearic acids. The unsaponifiable matter contains b-sitosterol. The oil-cake from crushing whole seeds contain 9.0% moisture, 6.5% oil, 20.5% protein, 49.0% total carbohydrate and 15.0% ash. The manural value is 6.6% N, 2.6% P2O5, and 1.2% K2O (C.S.I.R., 1948–1976). There are 60 mg/kg uric acid and 7 ppm HCN in the seed. The seeds contain a powerful lipase, employed for commercial hydrolysis of fats, also amylase, invertase, maltase, endotrypsin, glycolic acid, oxidase, ribonuclease, and a fat-soluble zymogen. Sprouting seeds contain catalase, peroxidase and reductase.
The Castor Ricin
The Castor seed contains the deadly poison ricin within it. This is how it gets its botanical name Ricinus communis
