Abstract
E. guineensis, the oil palm or African oil palm, is native to equatorial Africa, although the only other species in the genus (E. oleifera) is indigenous to South and Central America. E. guineensis, however, is the major economic species: fruits of E. oleifera have a much lower oil content and are used only locally (Westphal and Jansen, 1989). However, E. guineensis was introduced into South America during the time of the slave trade, and naturalized groves are reported in coastal areas of Brazil near Bélem. In the mid-1800s it was introduced to South-East Asia via the Botanic Gardens in Bogor, Indonesia. The first oil-palm estates in Sumatra (since 1911) and Malaysia (since 1917) used plant material from second- and third-generation descendants of the original Bogor palms, from which one of the breeding populations, the Deli Dura, is derived (Westphal and Jansen, 1989). After soyabean, E. guineensis is the second most important crop worldwide for the supply of edible vegetable oil. Palm oil kernel, for example, is a major agricultural export from Malaysia, and South-East Asia is the main area of production.E. guineensis yields two types of oil: palm oil from the fleshy mesocarp, and palm-kernel oil from the kernel, in a volume ratio 10:1. Most palm oil is used in food preparation (margarines, and industrial frying oils used to prepare snack foods, etc.). Palm-kernel oil is similar in composition and properties to coconut oil, and is used in confectionery, where its higher melting point is particularly useful. It is also used in the manufacture of lubricants, plastics, cosmetics and soaps. The oil palm is a monoecious, erect, single-stemmed tree usually 20-30 m high. The root system is shallow and adventitious, forming a dense mat in the top 35 cm of the soil. The main stem is cylindrical, up to 75 cm diameter. E. guineensis palm fronds are not as suitable for thatching as other palm species, as the leaflets attach to the rachis at two angles. The oil palm is indigenous to the lowland humid tropics, and thrives on a good moisture supply and relatively open conditions. It can tolerate fluctuating water-tables with periods of standing water, although continuously flooded conditions are unsuitable. Sites often selected as suitable for oil palm are swamps, riverbanks, or sites considered too moist for tropical rain forest trees. Rainfall is often the major factor limiting production in plantations: highest yields occur where rainfall is evenly distributed throughout the year, with an optimum of 150 mm per month (Westphal and Jansen, 1989). Oil palms can grow on a variety of soil types, from sandy soils to lateritic red and yellow podzols, young volcanic soils, alluvial clays and peat soils; water-holding capacity appears to be the most important soil criterion. It is a demanding crop in terms of soil nutrients. The oil palm also has potential for incorporation into agroforestry practices. Traditional oil palm management in some areas of West Africa often incorporated both pure oil palm groves (perhaps selectively retained), scattered oil palms within temporary fields, and unexploited oil palms in mixed forest (Gupta, 1993). Harvesting of fruits usually starts about 2½ years after field planting; bunches ripen throughout the year and so harvesting usually takes place at intervals of 2 to 3 weeks in any particular area. Because oil palm is so responsive to environmental conditions, yields may vary greatly. However, over the lifetime of a palm tree, yields generally rise to a maximum in the first 6-8 years (after field planting), and will subsequently decline slowly. In Malaysia and Sumatra, well-managed plantations yield between 24 and 32 tonnes/hectare of fruit bunches; the oil yield from this will be between 4.8 and 7 tonnes/hectare. Oil palm plantations are often regarded as a better use of the land than annual food crops in humid tropical areas where soils are prone to leaching: the plantations provide continuous ground cover, and the palm canopy helps protect against soil erosion. Oil palm stems are increasingly used as a raw material for paper and composite board production. This area has big prospects in wood-based industries. It is recommended that more research is undertaken into the properties and utilization. Propagation techniques, the management of pests and diseases, and genetic resources are other areas in which studies could usefully be undertaken.
Comparative study of tyre ash and palm kernel oil cake as back-filling agents for effective grounding
