Planting, cross breeding and disease of oil palm

Planting

For each hectare of oil palm, which is harvested year-round, the annual production averages 10 tonnes of fruit, which yields 3,000 kg of pericarp oil, and 750 kg of seed kernels, which yield 250 kg of high quality palm kernel oil as well as 500 kg of kernel meal. Palm fronds and kernel meal are processed for use as livestock feed^[7].
All modern, commercial planting material consists of tenera palms or DxP hybrids, which are obtained by crossing thickshelled dura with shell-less pisifera. Although common commercial pregerminated seed is as thick-shelled as the dura mother tree, the resulting tree will produce thin-shelled tenera fruit. An alternative is to pre-germinated seed, once constraints to mass production are overcome, is tissue-cultured or “clonal” palms which provide “true copies” of high yielding DxP palms.
It is essential for an oil palm nursery to have an uninterrupted supply of clean water and topsoil which is both well-structured and sufficiently deep enough to accommodate three rounds of on-site bag-filling. Approximately 35ha can grow enough seedlings over a three-year period to plant a 5,000ha plantation. Pre-nursery seedlings must be watered daily. Whenever rainfall is less than 10 mm per day, irrigation is required, and the system must be capable of uniformly applying 6.5mm water per day.
Pre-nursery seedlings in the four-leaf stage of development (10 to 14 weeks after planting) are usually transplanted to the main nursery, after their gradual adjustment to full sunlight and rigid selection process. During culling, seedlings that have “grassy”, “crinkled”, “twisted”, or “rolled” leaves are discarded.
Weeds growing in the polybags must be carefully pulled out. Herbicides should not be used. Numerous insects (e.g., ants, armyworm, bagworm, aphids, thrips, mites, grasshoppers, mealybugs) and vertebrates (e.g., rats, squirrels, porcupine, wild boar, monkeys) are pests in oil palm nurseries and must be carefully identified before control measures are implemented.
After eight months in the nursery, normal healthy plants should be 0.8–1 m in height and display 5 to 8 functional leaves.

Oil palm plantations in the municipality of Aracataca, Colombia.

The proper approach to oil palm development begins with the establishment of leguminous cover plants, immediately following land clearing. It helps prevent soil erosion and surface run-off, improve soil structure and palm root development, increase the response to mineral fertilizer in later years, and reduce the danger of micronutrient deficiencies. Leguminous cover plants also help prevent outbreaks of Oryctes beetles, which nest in exposed decomposing vegetation. Both phosphorus and potassium fertilizers are needed to maximize the leguminous cover plants’ symbiotic nitrogen fixation potential of approximately 200 kg nitrogen/ha/yr and are applied to most soils at 115 to 300 kg phosphorous oxide/ha and 35 to 60 kg potassium oxide/ha. Young palms are severely set back where grasses are allowed to dominate the inter-row vegetation, particularly on poor soils where the correction of nutrient deficiencies is difficult and costly.

[edit] Crop nutrient

Oil palm tree

Nutrient uptake is low during the first year but increases steeply between year one and year three (when harvesting commences) and stabilizes around years five to six. Early applications of fertilizer, better planting material, more rigid culling has led to a dramatic increase in early yields in third to sixth years from planting. In regions without any serious drop in rainfall, yields of over 25 tonnes of fresh fruit bunches per hectare have been achieved in the second year of harvesting.
Nitrogen deficiency is usually associated with conditions of water-logging, heavy weed infestation and topsoil erosion. Symptoms are a general paling and stiffening of the pinnae which lose their glossy lustre. Extended deficiency will reduce the number of effective fruit bunches produced as well as the bunch size.
Phosphorous deficient leaves do not show specific symptoms but frond length, bunch size and trunk diameter are all reduced.
Potassium deficiency is very common and is the major yield constraint in sandy or peaty soils. The most frequent symptom is "confluent orange spotting". Pale green spots appear on the pinnae of older leaves; as the deficiency intensifies, the spots turn orange or reddish-orange and desiccation sets in, starting from the tips and outer margins of the pinnae. Other symptoms are "orange blotch" and "mid-crown yellowing". In soils having a low water holding capacity (sands and peats) potassium deficiency can lead to a rapid, premature desiccation of fronds.
Copper deficiency is common on deep peat soils and occurs also on very sandy soils. It appears initially as whitish yellow mottling of younger fronds. As the deficiency intensifies, yellow, mottled, inter-veinal stripes appear and rusty, brown spots develop on the distal end of leaflets. Affected fronds and leaflets are stunted and leaflets dry up. On sandy soils, palms recover rapidly after a basal application of 50 grams of copper sulphate. On peat soils, lasting correction of copper deficiency is difficult, as applied copper sulphate is rendered unavailable. A promising method to correct copper deficiency on peat soil is to mix copper sulphate with clay soil and to form tennis-ball sized “copper mudballs” that are placed around the palm and that provide a slow-release source of available copper.
Healthy, well selected seedlings are a pre-condition for early and sustained high yield. In most cases granular multinutrient compound fertilizers are the preferred nutrient source for seedlings in the nursery. Where sub-soil is used to fill the polybags, extra dressings of Kieserite may be required (10-15 g every 6 to 8 weeks). Where compound fertilizers are not available, equivalent quantities of straight materials should be used.
To maintain good fertilizer response and high yields in older palms (selective) thinning is often necessary.

[edit] Cross-breeding

Oil palm fruit

Unlike other relatives, the oil palm trees do not produce offshoots; propagation is by sowing the seeds.
Before the Second World War, selection work had started in the Deli dura population in Malaya. Pollen was imported from Africa, and DxT and DxP crosses were made. Segregation of fruit forms in crosses made in the 1950s was often incorrect. In the absence of a good marker gene, there was no way of knowing whether control of pollination was adequate.
It was only after the work of Beirnaert and Vanderweyen (1941) that it became feasible to monitor the efficacy of controlled pollination. From 1963 until the introduction of weevils in 1982 contamination in Malaysia's commercial plantings was generally low. It appears that thrips, the main pollinating agent at that time, rarely gained access to bagged female inflorescences. However, E. kamerunicus is much more persistent, and after it was introduced D contamination became a significant problem. This problem appears to have persisted for much of the 1980s, but in a 1991 comparison of seed sources, contamination had been reduced to below 2% (Rao and Kushairi, 1999), indicating that control had been restored.
A 1992 study^[8] at a trial plot in Banting, Selangor revealed yield of Deli dura oil palms after four generations of selection was 60% greater than that of the unselected base population. Crossing the dura and pisifera to give the thin-shelled tenera fruit type improved partitioning of dry matter within the fruit, giving a 30% increase in oil yield at the expense of shell, without changing total dry matter production.

[edit] Disease

Basal stem rot, caused by the fungus ganoderma, is the most serious disease of oil palm in Malaysia and Indonesia. Previously, research on basal stem rot was hampered by the failure to artificially infect oil palm with the fungus. Although Ganoderma had been associated with BSR (Thompson, 1931), proof of its pathogenicity to satisfy Koch’s postulate was only achieved in the early 1990s by inoculating oil palm seedling roots (Ariffin and Idris, 1991) or by using rubber wood blocks (Khairuddin, 1990). A reliable and quick technique for testing the pathogenicity of the Ganoderma fungus by inoculating oil palm germinated seeds.^[9]
This fatal disease can lead to losses as much as 80% after repeated planting cycles. Ganoderma produces enzymes that degrade the oil palm tissue and affect the infected oil palm xylem thus causing serious problems to the distribution of water and other nutrients to the top of the palm tree.^[10] Ganoderma infection is well defined by its lesion in the stem. The cross section of infected palm stem shows that the lesion appears as a light brown area of rotting tissue with a distinctive irregularly shaped darker band at the borders of this area.^[11] The infected tissue become as an ashen-grey powdery and if the palm remains standing, the infected trunk rapidly become hollow.^[12]
In a 2007 study in Portugal, scientists suggest control of ganoderma on oil palms would benefit from further consideration of the process as one of white rot. Ganoderma are extraordinary organisms capable exclusively of degrading lignin to carbon dioxide and water: celluloses are then available as nutrients for the fungus. It is necessary to consider this mode of attack as a white rot involving lignin biodegradation, for integrated control. The existing literature does not report this area and appears to be concerned particularly with the mode of spread and molecular biology of ganoderma. The white rot perception opens up new fields in breeding/selecting for resistant cultivars of oil palms with high lignin content, ensuring the conditions for lignin decomposition are reduced, and simply sealing damaged oil palms to stop decay. It is likely that spread is by spores rather than roots. The knowledge gained can be employed in the rapid degradation of oil palm waste on the plantation floor by inoculating suitable fungi, and/or treating the waste more appropriately (e.g. chipping and spreading over the floor rather than windrowing).^[13]
Endophytic bacteria are organisms inhabiting plant organs that at some time in their life cycle can colonize the internal plant tissues without causing apparent harm to the host.^[14] Introducing endophytic bacteria to the roots to control plant disease is to manipulate the indigenous bacterial communities of the roots in a manner, which leads to enhanced suppression of soil-born pathogens. The use of endophytic bacteria should thus be preferred to other biological control agents as they are internal colonizers, with better ability to compete within the vascular systems, limiting Ganoderma for both nutrients and space during its proliferation. Two bacterial isolates Burkholderia cepacia(B3) and Pseudomonas aeruginosa(P3) were selected for evaluation in the glasshouse for their efficacy in enhancing growth and subsequent suppression of the spread of BSR in oil palm seedlings.^[15]
Little leaf syndrome has not been fully explained but has often been confused with Boron deficiency. The growing point is damaged, sometimes by Oryctes beetle. Small, distorted leaves that resemble Boron deficiency emerge. This is often followed by secondary pathogenic infections in the spear that can lead to spear rot and palm death.^[16]