Oil palm is an oil crop grown in the tropics. It is classified based on two criteria, which are types and fruit form.
(i) Fruit types
Under this, oil palm is classified on the basis of external variation (morphology). These include size of leaves, fronds, maturity, and adaptability to environment. External classification of oil palm into four fruit types is as follows:
(a) Nigrescens: This is the most common oil palm fruit type widely distributed throughout the world. It has black colour when unripe and crimson-red with top still black when ripe.
(b) Virescens: This is the oil palm fruit type which has green colour when unripe due to the absence of anthocyanic pigment. When ripe, the colour turns brick-red or reddish orange with top still green.
(c) Albescens: This is the classification of oil palm fruit type in which the fruit is almost white when unripe due to the absence of carotenoid pigments. When ripe, the colour turns pale yellow. The oil extracted from this fruit type is free of carotene content.
(d) Poissoni: This fruit type usually has a mantle of outgrowth around the main fruit.
(ii) Fruit form
Here oil palm fruits are classified based on the internal variation (Anatomy). The first form includes:
(a) Macrocarya form: This has a very thick shell usually 6-8mm thick. It has very thin pericarp and mesocarp. It yields low oil from its mesocarp. This is mostly grown in rainforest belt of West Africa.
(b) Dura form: This fruit form has large kernels and the mesocarp is fairly thin but not as thin as macrocarya. It yields a lower oil content than the macrocarya.
(c) Pisifem form: This usually has thick mesocarp, small kernel and has fibre rings. It is a very infertile palm and fruit rots prematurely. Pisifera is most often grown for breeding and not for commercial purpose due to low fruit retention capacity.
This is a cross between pisifera and Dura. It has thinner shell than Dura and thicker shells than pisifera. Tenera is grown on commercial basis due to its high oil content. It is extensively grown in many plantations in Rivers, Edo, Ondo States. It is produced at Nigerian Institute for Oil Research NIFOR, in Edo State, Nigeria.
Oil palm is a tropical crop. It requires high amount of rainfall and grows best where rainfall is between 1800 -2400mm per annum. Rainfall should be evenly distributed throughout the months of the year. Oil palm needs high temperature. The mean maximum temperature is 29-33degrees C and mean minimum of 22-24degrees C, seedling growth is stopped at 15 degrees C. It also requires a high amount of sunshine, deep loamy or sandy-loam soils with a loose pad that is rich in humus also with good porosity. Available nutrients include calcium, ca.magnesium, mg., with a pH range from 4-6 for optimum growth of oil palm.
The seeds of oil palm are planted in a temporary medium for all the seeds to fore sprout into seedlings using grounded, raised tray, and by the use of polybags as precursory materials. Sprouting of seeds into seedlings takes between 4-5 days. This pre-nursery practice is necessary as it ensures even germination of seeds into seedlings at a given range of time. The seedlings are then transplanted to the main nursery using raised wooden or concrete trays initially favoured by NIFOR and the standard dimension used was 45 inches x 21 inches x 6 (L x B x H). The trays were filled with sterilised top soil or peat or sand screened with X mesh sieve and tray are normally perforated (holes are bored into the tray) to ensure good drainage period of pre-nursery, which is between 4-6 months.
The nursery can also be raised using ground bed, raised tray, and polybags method. The seedlings at 4-5-leaf stage from the pre-nursery are normally transplanted to the main nursery and left to grow for about 9-12 months before finally transplanting the seedlings to the permanent site or field. The colour of the bag should be black. This is to function as a shielding medium from the high intensity of sunlight on the foliage leaves in the seedlings. The procedures in oil palm nursery practices include selection, preparation of site and planting. Under selection of site, this requires that the nursery site should be close to the permanent site or plantation that should be flat and fertile. Preparation of site, during nursery implies clearing, plowing, collection of top soil to fill polybags or raised. Keep polybags at correct spacing of 46cm square. Planting of the seedlings during nursery should be done in March/April, and completed in May. Ensure that the radicle points downwards and plumule upwards.
The post-nursery maintenance practices carried out after planting oil palm seedlings in the permanent site or field include: mulching, watering, shading, fertiliser application, weed control and pest control.
Mulch immediately after planting with decaying bunch refuse leaves or wood shavings.
Seedlings are supplied with adequate water using watering device such as watering can; Each polybag requires two litres of water applied one to two equal amounts weekly. Increased water supply to the seedling should be done during dry season and less during wet season. This is practised to promote the rapid growth of the seedlings in the medium.
In southern Nigeria, shading is not necessary if the nursery is established at the right time; but if nursery is established in the dry season, it is necessary to provide shade.
(iv) Fertiliser Application:
Mixture of N. P. K. Mg at the ratio of 1:1:1:2 is recommended. Nitrogen has to be in the form of (NH 4)2SO4, K as Murate of potash and Mg as Magnesium sulphate. This mixture has to be applied at the rate of 56g/seedling in the 2nd and 8th months after planting (note: there is no compound fertiliser for oil palm nursery). The application is made by removing the mulch and applying the fertiliser in a ring form around the palm seedling.
(v) Weed Control:
Oil palm seedling grows slowly and does not compete with weeds, thus remove the weeds as soon as they sprout. In the polybag nursery, remove weeds both inside and outside the polybag using hand. Herbicides may be used. These include Simazine and Duron applied at the rate of 2kg a.i/ha for the nursery. Do not use contact herbicides (paraquate or glyphosate) or phenoxic herbicides (2, 4 D and 2,4, 5, T) on oil palm nursery.
(vi) Pest Control:
The oil palm nursery is attacked by pests such as snails, crickets, caterpillars, grasshoppers, etc. Spray regularly with Di.thane M45.
This is the most expensive operation in oil palm industry. Procedures followed include:
(i) Choice of site:
The site chosen for oil palm plantation must meet these conditions: availability of large acres of land, accessibility to a major road, availability of water for nursery, the topography of the land must be flat, fertile soil, availability of adequate rainfall.
(ii) Land preparation:
The land preparation is carried out in steps through the following operations;
(a) Under brushing: This is simply cutting the undergrowth to allow easy access to the land.
(b) Lining Out: Planting points are marked out at distance of 9 metres triangular.
(c) Felling of Trees: The trees are felled in a different direction as the rows of palms are usually in a N-S direction. Felling is done using axes and matchets or motor saw as the case may be.
(d) Burning: The burning of the fallen branches of trees is done. If the plantation is established on farmland, the practice must be avoided. Burning reduces cost of clearing and allows work to take off in time, controls weeds and increases the Potassium content of the soil, but leads to loss of organic matter.
(iii) Spacing of layout:
This depends on the terrain of the land. For flat lands, the 9m triangular spacing should be adopted.
(iv) Field planting:
(a) Time of planting: It is most ideal to plant early in the rains. In Rivers State, it is best to plant in March/April. Planting of seedlings in the field should be completed before May.
(b) Holing: Holes should be dug prior to planting about 30cm, in sandy soil and larger holes of 60-90cm3 in heavy soils.
(c) Methods of planting:
(i) Ball of earth:
This is used for planting polybag seedlings which are planted with whole soil. During planting, care should be taken to remove the polybag without damaging the roots of the seedling. The ball of soil should be completely levelled but the surface of the ball should be in the same level as the soil surface such that the stem of oil palm is raised above the levelled soil.
(ii) Naked root system: It is adopted if plantation is far from the Nursery. The polybag and ball of earth should be removed before transportation. The root should be dipped in a clay slurry. Tie the seedlings in bundles (in sack, grasses or banana leaves). With this method, many seedlings can be transported easily. In this system, holes should be shaped like a cross with a slight elevation at the centre. Roots should be spread evenly in the four arms of the cross, fill the hole with top soil and press firmly. Note: Percentage establishment is greater in ball of earth method.
This is done to protect the young seedlings from rodents (squirrel) cutting-grass, porcupine, etc.) immediately after planting by the use of wire collar. The protection should be placed 30cm from the base of the seedlings, while the height of the wire collar should be 45cm and diameter of 23cm. In the absence of the wire collar, wire netting, split bamboo sticks could be used. Also keep domestic animals away from the plantation.
Replacement is carried out in order to fill the spaces created by plants which failed to grow as a result of stress or pest attacks in the field. It should be done at the early stage of the plantation establishment and in short in the first two years so as to enable the uniformity and the maturity of the plants, at the same period in the field.
(iii) Planting cover crops:
In Nigeria, mixture of three legumes are recommended for oil palm plantation, Calapogonum mucunoides, centrosema pubescens and Puereria phaseoloides. Seeds are mixed and planted. Calapogonum mucunoides and Centrosema pubescens seeds are usually soaked in concentrated sulphuric acid, H2SO4 for 15-20 minutes to break dormancy (inactive state of embryo’ in seed which prevents germination). Pueraria is soaked for 30 minutes and then washed with distilled water. Cover crops are advantageous in weed control, supply or organic matter, and protection of soil surface against erosion.
Weed control in oil palm plantation can be effectively carried out through manual, chemical or mechanical method.
(i) Manual method:
In manual method, hand slashing (cutlassing) is done regularly. Regular cutlassing 3-4 times a year is ideal for palm 1-8 years old, but beyond 8 years, cutlassing interval should be once in a year. It could be done as inter-row maintenance and also as ring weeding around the plant. Weeding 1 metre radius and 1.5m radius is normal for younger and older palm respectively, if ring weeding is adopted.
(ii) Chemical method:
In chemical method, contact and systemic herbicides are used. Some of these herbicides are Asalox, Ametryne, Paraquat, and simazine, Duron (aramaxone). Glyphosate is a selective herbicide. It kills other weeds except legumes. Knap sack is normally used in applying their formulations.
(iii) Mechanical method: Mechanical weed control is carried out using farm implements attached to tractors. The Implement includes slushier, mower, rollers and cultivators, etc. These are mainly used for interval maintenance in developed countries. But it may not be popular practice in Nigeria.
Oil palm is widely adapted to varied nutrients supply in soils. Optimum yields of oil palm is attainable in a large plantation when a compound fertiliser is applied containing Nitrogen, Phosphorus, Potassium and Magnesium in the ratio 12.12:12:12. (i.e N. P. K Mg. 12: 12: 12: 12). The fertiliser application is done according to the age of the oil palm at 6 weeks after planting (October), and 6 months after planting, the rate (Kg/palm) of N. P. K Mg are 1/4, 1/4, 1/4, 1/4, and 1/4, 1/4, (No. K, Mg) respectively, While, in the 1st year, 2nd year and 3-15 years of early rains (May). The fertiliser applications of the same nutrients are 1/2, 1/2, 1/2, 1/2, 1: 3/4, 3/4, 3/4, and 1: 3/4, 3/4, 3/4, respectively.
Harvesting of transplanting oil palms is done in 3-4 years when the fruit bunch just begins to lose a few fruits. The techniques of harvesting includes cutting of bunches from the tree using the farm implement such as go-to-hell or Malayan knife that can reach the ripe bunch of fruit which grow from the ground. The pole knife or Malayan knife is popularly called go-to-hell. Chisel method or use of climbing ropes are used for harvesting ripe oil palm fruits, collection of loose fruits and transportation. In the three methods of harvesting the fruits, it is only the fresh leaves which hinder the removal of the bunch. Hence should be cut off.
The processing of fruits may be carried out either by traditional or modern method. Traditional method: The processes involved in the traditional method are outlined below:
(i) Processing to obtain the loose fruit.
(ii) Boiling of the fruit (to soften the mesocarp and stop the formation of free fatty acids caused by the enzyme (lipases) which act on fats.
(iii) Pounding on wooden or ground based drum mortar.
(iv) Separation of the kernel from pulp by pressing out the oil using screw press.
(vi) Storage of oil for sale.
This is the method used for commercial scale production of palm oil in large oil palm estates.
(i) Sterilisation – This is carried out using horizontal or vertical steriliser. The length of time of sterilisation of fruits in the sterilizing equipment depends on the freshness of the fruit. Freshly harvested fruit should be kept for an hour. The sterilisation of fruits helps to kill the bacteria and fungi and stops the formation of free fatty acid. It also softens the mesocarp, which is the part containing the raw oil in the oil palm fruits.
(ii) Stripping of the fruits from the bunch.
(iii) Maceration (Depulping or digestion) and separation of the pulp from the kernel. The kernel is pressed to produce kernel oil.
(iv) Oil extraction using hydraulic press, screws or centrifugal press.
(v) Clarification of the oil – Oil is mixed with water and boiled.
(vi) Effluent (foamy portion containing water) is removed.
Economic importance of oil palm
(i) Palm oil is the most economically valuable product of oil palm. It is used for cooking food. It is a raw material for soap, margarine and candle making, it is also bleached and used in pomade.
(ii) Kernel: The kernel is processed into kernel oil and palm kernel cake and meal. The kernel oil is medicinal, used in confectioneries, margarine, candle pomade, ice-cream, etc. The meal is used as livestock feed.
(iii) Palm wine tapped from the male inflorescence is also valuable for consumption. Alcohol can be distilled from fermented palm wine.
(iv) Palm bunch refuse is rich in potassium and is used for locally manufactured material. Palm trunk is sawn into timber for building and fencing.
(vi) Kernel shells are used for fuel.
(vii) It earns foreign exchange from export.
(viii) It provides employment.
Oil palm diseases
(a) Antracnose Disease
Causative agent: Fungus.
Species: Botryodiplodia, Palmarum, Melanconium, Elacidis, and Glomerella cingulata and corticium solani.
Transmission: It is transmitted by air-borne spores, which attack plants.
(i) Appearance of brown-black spots along the margin or centre of the leaf.
(ii) Rottening of the infected part.
Prevention and Control:
(i) By applying fungicides such as Dithane M45, 2g/litre. Captan, cuman 6, ziram and perenox.
(ii) By regular weed control in the field.
(iii) Avoidance of overcrowding in the Nursery because it is a nursery disease.
Causative agent: Fungus.
Species: Cercospora elaeidis.
Transmission: It is transmitted through air-borne spores deposited on leaves. It is both a nursery and field disease.
(i) Appearance of brown spots which is surrounded by yellow orange spots.
(ii) Stunted growth.
(iii) It causes spots to coalesce and drying out of tissues.
(i) By good cultural practices such as weeding.
(ii) By spraying fungicides.
Causative agent: Fungus.
Species: Piricularia SPP e.g. Pythium and Phizoctonia.
Transmission: It is a transmitted by soil-borne mycelium which attack the roots of oil palm. It is a root disease of oil palm seedlings. It is common in dry periods.
(i) Necrosis of leaves.
(ii) Change of colour from dull green to brown.
(iii) Rottening of roots.
(iv) Withering of seedlings.
(v) Death of plant.
(i) Adequate watering of plants.
(ii) Planting viable seedlings.
(iii) By spraying at regular intervals with fungicides such as Captain.
(d) Vascular wilts
Causative agent: Fungus.
Species: Fusariun oxusporium.
Transmission: It is transmitted by soil-spores of fungus on young leaves of plants.
(i) Young leaves turns bright-yellow.
(ii) Reduced leaves in plants.
(i) By good cultural practices -stumping before transplanting.
Causative agent: Bacterium.
Species: Fusariun Ozysporium.
Transmission: It is transmitted by soil-borne bacteria which infects the plants through wounds caused either by insects or nematodes.
Leaves break at the base and drag downward.
(ii) Death of plants.
(i) By good cultural practices, such as weeding, and fertiliser application.
(ii) By avoiding infected soil.
(f) Brown Germ
Causative agent: Fungus.
Transmission: It is transmitted by the hyphae which spread on oil palm fruit.
(i) Brown spots appear on leaves.
(ii) Rottening of plants tissues.
(i) By spraying with fungicides.
(ii) Deformed colour due to coalesce, orange spots in severe attack. Pest of Oil Palm.
(iii) These includes, mites, termites, grasshopper aphids, mealybugs, rodents, caterpillars, stroope weevil, spear borer.
(g) Algal spot.
Causative agent: Cephaleuros virescens.
Transmission: It is soil-borne alga infection.
Appearance of orange spots on leaf margin.
(i) Spraying insect pests with insecticides.
(ii) Using traps to control rodents.
(iii) Mites, termites, spear borers are effectively controlled by spraying with Rogor 40.
Oil palm is an oil crop grown in the tropics. It is classified based on two criteria which are fruit types and fruit form. It is under fruit type that oil palm is classified on the basis of its external variation, while under fruit form, oil palm is classified based on its internal variation. Oil palm grows well in a soil with deep loam or sandy-loam and on a soil pH range from 4-6 for optimum growth. It requires a high amount of rainfall.