Oil Palms (Elaeis guinensis Jacq.), from Greek, meaning “oil”, belongs to palm family, used in commercial agriculture in the production of palm oil. Oil is extracted from both the pulp of the fruit (palm oil, an edible oil) and the kernel (palm kernel oil, used in foods and for soap manufacture). Mature trees are single-stemmed, and grow to 20 m tall. The leaves are pinnate, and reach between 3-5 m long.
Introduction
Oil palm requires evenly distributed annual rainfall of 2000 mm without a defined dry season. In areas with dry spell, a deep soil with high water holding capacity and a shallow water table augmented with copious irrigation will satisfy the water requirement of the palm.
Temperature can be a limiting factor for oil palm production Best oil palm yields are obtained in places where a maximum average temperature of 29-33oC and minimum average temperature of 22-24oC are available. Higher diurnal temperature variation causes floral abortion in regions with a dry season.
The crop requires 1800-2000 sunlight hours annually, more than 300 cal/cm2 / per day, constant sunlight of at least 5 hours per day for better oil palm yield.
Moist, deep and well drained medium textured soils rich in humus content are considered ideal. Gravelly and sandy soils, particularly the coastal sands are not ideal for oil palm cultivation. Heavy clay soils with poor drainage properties may pose problems of aeration during rainy seasons.
How to grow Oil Palm:
Nursery and Management
Nursery is raised by planting germinated sprouts initially in a pre-nursery bed or in polybags in a primary nursery and transplanting them at five leaf stage to a secondary nursery of large sized polybags. Raising seedlings in large polybags without a pre-nursery stage is also being practiced.
The potting mixture is made by mixing top soil, sand and well decomposed cattle manure in equal proportions. Smaller polybags of 250 gauge and 23 x 13 cm size, preferably black are used for raising primary nurseries. These bags are filled with the potting mixture leaving one cm at the top of the bag. A healthy germinated sprout is placed at the center at 2.5 cm depth. While placing the sprout, care must be taken to keep the plumule of the sprout facing upwards and the radicle downwards in the soil. It is better to plant sprouts soon after the differentiation of radicle and plumule. The seedlings are to be watered daily. Application of a fertilizer mixture containing one part of ammonium sulphate, one part of super phosphate, one part of muriate of potash and two parts of magnesium sulphate is recommended at 15 g at one month stage, 45 g at three months stage and 60 g at six months stage per seedling. This has to be applied 6 – 8 cm away from seedlings during the first application, 10-12 cm away during second and 15-20 cm away during the third application in primary nursery. Surface soil is slightly scratched at the time of fertilizer application.
Single Stage Poly Bag Nursery and Secondary Nursery
The germinated seeds can be directly planted into large black polybags with the advantage of avoiding the pre-nursery stage. At present the single stage polybag nursery is recommended in India. Since the plants are to remain in these polybags for more than one year, good quality polybags of 500 gauge and 40 x 45 cm size are to be used. On the lower half of the bag, perforations are made at an interval of 7.5 cm for drainage. A bag can carry 15 – 18 kg of nursery soil depending on the type of soil mixture used.
The water requirement for different stages of growth of seedlings are as follows: 0 – 2 months at 4 mm/day, 2 – 4 months at 5 mm/day, 4 – 6 months at 7 mm/day and 6 – 8 months at 10 mm/day. It is better to supply if feasible the daily requirement in two halves to prevent overflow and wastage caused by one time application. Application of 9 – 18 lit. of water per seedling per week according to the stage of growth and soil type.
Field Planting
Prepare the land for oil palm plantings at least 3 months before transplanting the seedlings to the main field. In soils with low permeability, drainage channels are to be constructed to prevent water stagnation in upper layer of soil.
Age of Seedlings at Transplanting
It is advisable to plant well grown seedlings of 12 – 14 months old. At this stage, a well developed tenera seedling will have a height of 1-1.3 m from base and will have more than 13 functional leaves. These seedlings were found to maintain higher leaf production, bear earlier, produce heavy bunches, give higher fruit/bunch ratio and a higher oil to mesocarp in the first year of harvest.
Selection of Seedlings
All deformed, diseased and elongated seedlings are to be discarded. Differences in the height of healthy seedlings ranging from 90 to 159 cm tend to even up after 14 months of transplanting to maintain.
Time of Transplanting
Transplanting to the main field has to be done during the onset of rainy season. In very impermeable soils and where there is chance for the seedlings to suffer severely during rainy season, proper drainage has to be ensured.
Spacing and Method of Planting
The optimum planting density for oil palm is the density of population that gives maximum production from unit area. Triangular system of planting with 9 x 9 x 9 m spacing accommodates 143 palms/ha. is being recommended. For efficient utilization of solar energy the rows are to be oriented in the North-South direction. Equilateral triangular system of planting with 9 m spacing between palms will allow each plant to occupy the centre of a hexagon thus allowing better use of the area.
Transporting Seedlings and Preparing Pits
While transporting seedlings to the planting site one hand is placed at the bottom of the bag while holding the plant collar with the other one. Leather gloves can be used to avoid injury with spines of the leaves.
Pits of 60 cm3 are taken prior to planting and filled with surrounding top soil and allowed to settle. Rock phosphate is applied at 200 g per planting pit. Nitrogen is not usually applied in the planting pits as the application of fertilizers may damage the root system and affect survival of the plants if there is a dry period soon after planting. Nitrogen and potassium are usually applied 4 – 6 weeks after planting. In Mg deficient soils, magnesium is applied at 100 g as anhydrous MgSO4 or 200 gram salt per seedling.
Replacement and Gap Filling
Field inspection is carried out one to two months after planting to gap fill dead plants. Replanting is carried out during the onset of next monsoon. These palms are to be given special care so that they can catch up with the rest of the plantations. Early production of more female inflorescence in the initial 30 months, is an indication of high yields and all those that fail to produce female bunches will remain as poor yields. However, replacements are found to be affected to some extent by the vigorous growth of the neighboring palms which will shade the replanted palms.
Fertilizer Requirement
Based on the fertilizer experiments conducted under rain fed conditions in India, the following fertilizer schedule is recommended for oil palm until specific results are derived from multilocational fertilizer trials.
Method of Fertilizer Application
The fertilizers are preferably applied in two equal split doses during May – June and September -October by uniformly spreading them within a 2 meter circle around the base of the palm and forking to incorporate them into the soil. Supply of sufficient quantity of green leaves or compost is advantageous especially where the soil is poor in organic matter content. Mg deficiency can be corrected through the application of 500 g of MgSO4 /palm/year.
Urea is found to be the most economic nitrogen source if losses by volatilization and leaching are minimized. Rock phosphate and muriate of potash are the best source for phosphorus and potassium respectively. During the initial years fertilizers may be applied within the area covered by the crown canopy. In the case of older palms, fertilizers are applied depending on the concentration of roots and are usually applied in the weeded circle. Appropriate soil conservation methods such as growing cover crops and platform cutting (on sloppy lands) enhance the efficiency of fertilizers by preventing losses through run off.
Water Requirement
Continuous soil moisture availability encourages vigorous growth and increased yield of oil palm. Adequate supply of water, good soil depth and water holding capacity contribute to water availability. In oil palm as water deficiency increases, stomata will remain closed and the development and opening of spear will be inhibited. Water deficiency adversely affects flower initiation, sex differentiation and therefore, results in low sex ratio due to production of more male inflorescences. It is established that oil palm needs 120 – 150 mm of water to meet its monthly evapo-transpiration needs. In areas where perennial water source is available, basin irrigation is possible. But where the terrain is undulating and water is scarce during summer months, drip irrigation is recommended to keep four drippers per palm in the weeded palm circle to supply at least 90 liters of water per palm per day during summer months which will vary according to the ETP values in a locality.
Weed Control
The basin area of oil palm is kept free of weed growth through ring weeding. It is more important for young palms, roots of which are to be kept free from competition from weed. Depending on the extent of weed growth and rainfall, hand weeding is carried out even up to four times in a year during early years of the plantation which is progressively reduced to two rounds a year.
Herbicide application has become common in recent years. Care must be taken in the choice of herbicide and its application to prevent the damage of young palms. It is recommended to preferably apply contact herbicides rather than translocated herbicides. Translocated herbicides like Paraquat which is inactivated when contacted with soil are also used. Herbicides such as 2, 4-D, 2, 4-5-T, halogenated aliphatic acids Dalapon and TCA are found to produce abnormalities in oil palm seedlings and are to be avoided. Herbicide mixtures of 2 kg a.i. of Paraquat with 3 – 4 kg Atrazine Monuron and Diuron per ha sprayed/ground applied twice a year has been found to give control of weeds.
Maintenance of Paths
In young plantation, the maintenance of paths is important for inspection and in later years for harvesting. This is carried out by timely weed control as done in the case of ring weeding.
Ablation
The bunches produced initially will be very small and have low oil content. Removal of such inflorescences is called ablation or castration. Removal of all inflorescences during the initial three years is found to improve vegetative growth of young palms so that regular harvesting can commence after three and half years of planting. Ablation is done at monthly interval by pulling out the young inflorescence using gloves or with the help of devices such as narrow bladed chisels. Ablation improves drought resistance capacity of young palms by improving shoot and root growth especially in low production areas where dry condition exists.
Pruning of Leaves
In oil palm two leaves are produced per month. Therefore, it becomes necessary to prune excess leaves so as to gain access to bunches for harvest. Severe pruning will adversely affect both growth and yield of palm, cause abortion of female flowers and also reduce the size of the leaves. It was suggested that palms aged 4 – 7 years should retain 6 – 7 leaves per spiral (48 – 56), those aged 8 – 14 years 5 – 6 leaves per spiral (40 – 49) and those above 15 years should have 4 – 5 leaves per spiral (32 – 40). Leaf pruning is carried out in India using chisels so that leaf base that is retained on the palm is as short as possible or otherwise it may catch loose fruits, allow growth of epiphytes and the leaf axils form a potential site for pathogens. The leaf petioles are removed by giving a clear cut at a sufficient distance from the base of the petiole using a sharp chisel for young palms and with the long sickle in taller palms.
Pruning is preferably carried out at the end of the rainy season. It is also better to carry it out during the low crop season when laborers are also available. Pruning is confined to only lower senile leaves during initial harvests but when canopy closes in later years, leaves are cut so as to retain two whorls of fronds below the ripe bunch.
Insect pollination in oil palm
The oil palm, hitherto though to be wind pollinated, has been now proved to be an a insect pollinated species. From West Africa, the original home of oil palm, eight species of pollinating weevils were reported. Occurrence of Eldeidobius kamerunicus in the oil palm plantations of Kerala was introduced during 1985 from where it was introduced and got established in little Andamans during 1986.
The weevils are dark brown in color. Adult weevils feed on the anther filament. Eggs are deposited inside the male flowers and larva feeds on the spent flowers. Life-cycle is completed within 11 to 13 days. Males live longer than females. The activity of the insects is in accordance with the receptivity of the male and female inflorescences. It was roughly estimated that 40 palms in a grove might be the minimum to sustain a sufficiently high continuous population of pollinators to pollinate. All are receptive female inflorescences. The weevils carry maximum pollen during the third day of antheses. Antennae, rostrum, thorax, legs etc. are the main sites of pollen land. E.kamerunicushas a fairly good searching ability. It can survive in dry as well as in wet seasons.
Introduction of weevil in India increased the fruit let from 36.8 percent to 56.1 percent resulting in 40 per cent increase in F/B ratio. The maximum attainable pollination potential was as much as to cent percent with 57 percent increase in FFB weight.
For introduction, male flowers cut from palms which have the weevils are transferred to a plantation where one wishes to introduce. In order to make sure that they are not carrying any plant pathogens to other area/countries, we have to breed them under laboratory conditions for seven or eight generations before introduction.
Harvesting
Proper and timely harvesting of fruit bunches is an important operation which determines the quality of oil to a great extent. The yield is expressed as fresh fruit bunches (FFB) in kg per hectare per year or as oil per hectare per year. The bunches usually ripen in six months after anthesis. Unripe fruits contain high water and carbohydrate and very little oil. As the fruit ripens oil content increase to 80 – 85% in mesocarp. Over ripe fruit contains more free fatty acids (FFA) due to decomposition and thus increases the acidity. Usually the ripe fruits, attached to the bunches contain 0.2 to 0.9% FFA and when it comes out of extraction plant the FFA content is above 3%. Ripeness of the fruit is determined by the degree of detachment of the fruit from bunches, change in color and change in texture of the fruit. Ripening of fruits start from top downwards, nigrescens fruits turning reddish orange and the virescens (green) to reddish brown. Fruits also get detached from tip downward in 11 – 20 days time. Ripeness is faster in young palms than in older palms for the bunches of equal weight. The criteria used in determining the degree of ripeness based on the fruit detachment are as follows:
- a) fallen fruits: 10 detached or easily removable fruits for young palms and 5 for adult palms,
- b) number of fruits detached after the bunch is cut; 5 or more fruits/kg of bunch weight,
- c) quantity of detachment per bunch; fruit detachment on 25% of visible surface of bunch.
These criteria could be applied with flexibility.
Frequency of Harvesting
Harvesting rounds should be made as frequent as possible to avoid over ripening of bunches. A bunch which is almost ripe but not ready for harvest for a particular harvesting round should not be over-ripe by next round. In lean period of production, harvesting can be made less frequent and it should be more frequent in peak periods. Harvesting rounds of 7 – 14 days are generally practiced. Other factors determining frequency are, extraction capacity of the mill, transportation facilities, labor availability and skill of the workers. In India, harvesting is usually carried out with a chisel of 6 – 9 cm wide attached to a wooden pole or light hollow aluminum pipe, Bunches are cut without damaging the petiole the leaf that supports it. Use of narrow chisel is usually carried out till the palm reaches two meters above the ground. For taller palms up to 4 meters, a wider chisel of 14 cm is used. The curved knife is attached to a long bamboo or aluminum pole with screws or steel wires to harvest from taller palms. In uneven stands, an adjustable, telescopic type of pole is in use.
Yield of Oil Palm
In well maintained garden the yield of oil palm will be as furnished below:
Source: agritech.tnau.ac.in, en.wikipedia.org; Photos: agritech.tnau.ac.in