Papers : Oil Palm Agronomy

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Selected Papers in International Journals

Moradi, A., Teh, C.B.S., Goh, K.J., Husni, M.H.A. and Ishak, C.F. (2013) Decomposition and nutrient release temporal pattern of oil palm residues. Annal Applied Biology (In press)

Moraidi, A., Teh, C.B.S., Goh, K.J., Husni, M.H.A. and Fauziah, C.I. (2013) Soil organic C sequestration due to different oil palm residue mulches. In: Hamdan J. & Shamshudin, J. (Eds.). Advances in tropical soil science. Vol. 2. University Putra Malaysia, Serdang. (Accepted).

Ooi S.E., Choo C.N., Zamzuri .I, and Ong-Adullah M. ,2013. Candidate hormone-responsive markers for callogenesis of oil palm (Elaeis guineensis Jacq.). Journal of Oil Palm Research, 25(1): 9-21.

Lee, Y.P., Goh, K.J. and Teh, C.B.S. (2013) Effects of various acidity levels on the growth of oil palm seedlings and their nutrients uptake. In: Hamdan J. & Shamshudin, J. (Eds.). Advances in tropical soil science. Vol. 2. University Putra Malaysia, Serdang. (Accepted).

Ng, P.H.C., Goh, K.J. and Mahamooth, T.N. (2013) Challenges in fertiliser and cover crop management. The Planter 89 (1047): 409 – 431

Kok, S.M., Goh, Y.K., Tung, H.J., Goh, K.J., Wong, W.W. and Goh, Y.K. (2013) In vitro growth of Ganoderma boninense isolates on novel palm extract medium and virulence on oil palm seedlings. Malaysian J. Microbiology 9(1): 33 – 42.

Melling, L., Chaddy, A., Goh, K.J. and Hatano, R. (2013) Soil CO2 fluxes from different ages of oil palm in tropical peatland of Sarawak, Malaysia as influenced by environmental and soil properties. Acta Hort. 982, ISHS 2013 (Proc. IS on Responsible Peatland Mgt. & Growing Media Production): 25 – 36.

Melling, L., Tan, S.Y., Goh, K.J. and Hatano, R. (2013) Soil microbial and root respirations from three ecosystems in tropical peatland of Sarawak, Malaysia. J. Oil Palm Research 25 (1): 43-56.

Moraidi, A., Teh, C.B.S., Goh, K.J., Husn, A.M.H. and Fauziah, I. (2012) Evaluation of four soil conservation practices in a non-terraced oil palm plantation. Agronomy J. 104 (6): 1727 – 1740.

Ooi S.E., Choo C.N., Zamzuri I. and Ong-Adullah M. 2012. A candidate auxin-responsive expression marker gene, EgIAA9, for somatic embryogenesis in oil palm (Elaeis guineensis Jacq.). Plant Cell Tiss Organ Cult, 110: 201-212.

Kimura, S.D., Melling, L. and Goh, K.J. (2012) Influence of soil aggregate size on greenhouse gas emission and uptake rate from tropical peat soil in fores and different oil palm development years. Geoderma 185-186: 1-5.

Lee, Y.P., Teh, C.B.S., Goh, K.J. and Moraidi, A. (2012) Effects of four soil conservation methods on soil aggregate stability. Malaysian J. Soil Sci. 16: 43 – 56.

Teh, C.B.S., Goh, K.J., Law, C.C. and Seah, T.S. (2011) Short-term changes in the soil physical and chemical properties due to different soil and water conservation practices in a sloping land oil palm estate. Pertanika J. Trop. Agric. Sci. 34(1): 41-62.

Ng, P.H.C., Gan, H.H. and Goh, K.J. (2011) Soil nutrient changes in Ultisols under oil palm in Johor, Malaysia. J. Oil Palm and the Environment 2: 93 – 104.

Tang, S.Y., Hara, S., Melling, L., Goh, K.J. and Hashidoko, Y. (2010) Burkholderia vietnamiensis isolated from root tissues of Nipa palm (Nypa fruticans) in Sarawak, Malaysia, proved to be its major endophytic nitrogen-fixing bacterium. Bioscience, Biotechnology and Biochemistry 74(9): 1972-1975.

Teh, C.B.S., Goh, K.J. and Kamarudin, K.N. (2010) Physical changes to oil palm empty fruit bunches (EFB) and EFB mat (Ecomat) during their decomposition in the field. Pertanika J. Trop. Agric. Sci. 33 (1): 39-44.

Petronella G. A., Mohd, K. Y., Nik, M. M., Goh, K. J. and Gan, H. H. 2009. Effect of N and K Fertilizers on Nutrient Leaching and Groundwater Quality under Mature Oil Palm in Sabah during the Monsoon Period. American Journal of Applied Sciences 6 (10): 1788-1799.

Anuar A.R., Goh K.J., Tee B.H. and Ahmed O.H. 2008. Spatial variation of soil inorganic N in a mature oil palm plantation in Sabah, Malaysia. American Journal of Applied Sciences 5 (9) : 1239-1246.

Anuar, A.R., Goh, K.J., Tee, B.H. and Ahmed, O.H. 2008. Spatial-temporal yield trend of oil palm as influenced by nitrogen fertilizer management. Am. J. Applied Sciences 5(10): 1376-1383.

Anuar, A.R., Goh, K.J., Tee, B.H. and Ahmed, O.H. 2008. Transforming spatial-temporal yield maps to classified management zone maps for efficient fertilizer management of oil palm. Am. J. Applied Sciences 5(10): 1392-1396.

Melling, L., Hatano, R. and Goh, K.J. 2007. Nitrous oxide emissions from three ecosystems in tropical peatland of Sarawak, Malaysia. Soil Science and Plant Nutrition 53: 792-805

Melling, L., Hatano, R. and Goh, K.J. 2006. Short-term effect of urea on CH4 flux under the oil palm (Elaeis guineensis) on tropical peatland in Sarawak, Malaysia. Soil Science and Plant Nutrition 52: 788-792.

Soh, A.C., Goh, K.J. and Kee, K.K. 2006. Research and innovation toward sustainable palm oil production. Journal of Science and Technoloy in the Tropics 2: 77-95.

Melling, L., Hatano, R. and Goh, K.J. 2005. Global Warming Potential of Tropical Peatland of Sarawak, Malaysia. Phyton – Annales Rei Botanicae Special Issue (APGC 2004) Vol. 45 (4): 275 – 284.

Melling, L., Hatano, R. and Goh, K.J. 2005. Methane fluxes from three ecosystems in tropical peatland of Sarawak, Malaysia. Soil Biology and Biochemistry 37: 1445 – 1453.

Melling, L., Hatano, R. and Goh, K.J. 2005. Soil CO2 flux from three ecosystems in tropical peatland of Sarawak, Malaysia. Tellus 57B: 1-11.

Ooi L.H. and Heriansyah 2005. Palm pulverization in sustainable oil palms replanting. Plant Production Science 8 (3): 345-348.

Soh A.C. 2004. Selecting the ideal plant : what you see is not necessarily what you get. Journal of oil palm research Vol 16 No. 2 : 121-128.

Soh A.C., Gan H.H., Wong G., Hor T.Y. and Tan C.C. 2003. Estimates of within family genetic variability for clonal selection in oil palm. Euphytica, Kluwer Academic Publishers, Netherlands 133 : 147-163.

Soh A.C., Wong G., Hor T.Y., Tan C.C. and Chew P.S. 2003. Oil palm genetic improvement. In: Janick, J. (ed.) Plant Breeding Reviews Vol. 22. John Wiley & Sons, New Jersey, pp. 165-219.

Cocoa: Weed Control

Effects of weeds on cocoa

There is very little information reported in Malaysia or elsewhere on the effects of weeds on growth or yield of cocoa. Wood (1975) has cited a few references from Ghana and Trinidad where it appears that improved weed control is beneficial to growth and the number of seedlings that needed replacement. Brown and Boeteng (1972) obtained best growth of seedlings with spraying paraquat alone compared to paraquat followed up with dalapon and hand weeding (Table 5).

Table 5 : Effects of weed control on cocoa stem diameter (cm) in Ghana
(Brown and Boateng, (1972)

In Malaysia although there is no trial data, it is obvious from observations that cocoa seedlings grow poorly in weedy conditions and that seedlings in such areas are frequently very uneven in growth.

Weeds probably affect growth of cocoa in the following manner:-

• Compete for moisture
• Compete for nutrients
• Compete for light i.e. shade out the cocoa
• Climb up and ‘choke’ plants
• Cause poor access
• Affect growth of the shade plants in much the same manner as for cocoa and thereby affect the growth of young cocoa seedlings.

In the stages of early growth, moisture stress in particularly critical to the young cocoa seedlings. To reduce the stress, the cocoa plants defoliate their lower leaves. This has a subsequent severe effect on rate of establishment, early growth and initial yields from the loss of photosynthetic capability and nutrient reserves in the leaves.

It is therefore especially important that weed competition is minimal during early growth stages of the cocoa plant. This will enable good even growth which is an essential ingredient for high early yields.

From the third year in a well-established cocoa planting canopy coverage of the ground is significant and the heavy shade from the cocoa has greatly reduced weed growth. However in uneven plantings, usually also accompanied by high light availability, weed growth is still vigorous and competition could be significant still.

Weed problems are usually minimal in the good stands of cocoa from the fifth year when thick canopy coverage and layer of cocoa litter has been built up.

Weed Control programmes

The main aims of the weed control programme should be:-

• to minimize competition for moisture
• to minimize competition for nutrients
• to prevent weeds climbing up and engulfing the plants
• to allow easier access to the bushes for field operations

As discussed earlier, weed competition is more critical in young cocoa and weed control programmes should reflect this. The weed control programmes may therefore be broken down to the following stages:-

• Pre-planting
• Establishment of shade
• Young immature cocoa in pre-jorquette, say 0-½ year
• Immature cocoa, say ½-1½ year.
• Young mature cocoa, say 1½ – 4 years
• Mature cocoa, say 5 years +

Measures recommended are given in Appendix 1.

APPENDIX 1 Weed Control Programme in Cocoa

1. Pre-planting stage. No cocoa or shade trees have been planted and the opportunity should be taken, if possible and feasible, to eradicate perennial weeds and all creepers. At this stage, the most effective chemicals against the weeds may be used as no cocoa or shade plants are present. Such opportunities are most applicable in plantings from belukar or regenerated secondary jungle and probably least applicable under thinned jungle.

2. Establishment of shade. In under thinned jungle situations, where there have been no delay after thinning and in planting up of the permanent shade stand, weed problems are usually minimal and confined mainly to thinning out unwanted trees and spot spraying of weeds which have established in the open areas.

However, if as sometimes is the case, there have been delays or hold-ups after thinning or the jungle has been thinned by natural causes including fires, there could be massive regeneration of weeds which need to be controlled for quick and successful establishment of the shade trees to be planted.

When plantings are monoculture cocoa and planted shade are to be established, regular weed control rounds are required. Usually strips along the planting rows are sprayed regularly to minimize competition.

In attempting to achieve high early yields and to minimize shade manipulation, often shade levels are kept minimal in thinned jungle plantings. This predisposes weed growth especially where seed build-up has occurred after delays in planting programmes etc.

In monoculture cocoa where good uniform establishment of shade is essential for successful and even establishment of cocoa, the weeds must be kept under control for the shade trees to grow well. Usually under these conditions, light is not a constraint and weed growth is luxuriant unless controlled. Weed problems may be expected to be more severe in mono-cocoa areas than under thinned jungle.

3. Young immature cocoa areas. At time of planting cocoa, usually shade levels are between 20-40% in well prepared areas and weed seed build-up has been substantial especially in mono-cocoa areas. It is usual to spray out a blanket herbicide spray to suppress the weed growth before cocoa is planted.

Growth of the cocoa seedlings is not as good initially in cleared jungle areas so that allowance for this in the weeding programme should be given.

Regular weeding programmes are essential to obtain good establishment and even growth. Minimal weed competition at immaturity will allow good and even growth of the planting which in turn will shade out the weed more quickly thereby reducing overall weed control effort.

Hand weeding is recommended initially to ensure minimal damage to the seedlings in case of accidental spray drift.

4. Immature cocoa areas. Regular weeding rounds are still required as considerable light is still available to the weeds still. A good stand will reduce weeding problems so that the policy of full stands and supplying dead/vacant points and poorly growing plants has a beneficial effect on weed control.

At this stage only herbicide spraying is preferred for maintaining the rings and strips as there is minimal damage to roots and soil disturbance.

5. Young mature cocoa areas. Weed problems are expected to be much reduced at this stage as shade from the cocoa canopies increase. Particular problems are expected from the more open areas and where cocoa growth has not been good or where poor growth/vacant points exist. As the weeds present are expected to further retard growth if not controlled, a two-pronged effort to attain good weed control and promote growth of the plants through mulching, additional fertilizer and shade etc. is often required.

6. Mature cocoa areas. At this stage, weed control should be minimal and confined to areas between canopies where there is more light. By now all excess shade trees should have been removed.

The weed control programme are therefore based on the following principles:-

• minimise weed problems before planting of shade trees and cocoa
• good weed control in establishment phase of shade trees and cocoa by following regular weeding rounds
• differential weed control techniques depending on growth of cocoa and amount of light expected which affects weed growth
• allowing low soft grasses to establish where competition with cocoa is minimal so that run-off and erosion is minimised. In mature cocoa especially, they may also be useful in reducing nutrient loss from the fertilizer applications made.

As far as possible, weed control measures should be timed in conjunction with fertilizer applications. Otherwise weeds present may take up nutrients needed by the cocoa and reduce the growth of the latter.

While the above are direct measures taken on the weeds, as inferred from the discussions, ensuring good growth of the cocoa is also an effective means of the cocoa.

Mulching of the bushes with empty waste bunches of oil palm or coconut husk and similar materials is particularly to be encouraged as it promotes growth and reduce weed growth directly. Where possible this should be considered especially in special situations eg. supplies, very open areas, compact soil areas etc.

A guide on palm circle size or strip width to be kept clean for various ages of cocoa plants and shade trees (Gliricidia) is given in Table 6.

Table 6 : Recommended circle or strip sizes for cocoa

na = not applicable

Strip spraying is usually preferred when weed growth is thick as access is also improved.

Hand-weeding in cocoa

Weeding by hand with a small light changkol or sickle is recommended only in the first few months after planting when the plants are small and have no brown bark. The weeds should be removed without disturbance or damage to the cocoa roots and soil. To achieve this, there should be minimal scraping of the soil.

Good supervision is very important and care taken that plants are not damaged or even cut especially in thick weed conditions.

Herbicides for weed control in cocoa

In view of the shallow and superficial roots of cocoa, control of weeds by herbicides in cocoa is preferable to hand weeding with changkol or sickle. However, especially when the plants are small, serious damage may be caused by herbicide drift.

Commencement of use of herbicide spraying in cocoa should therefore be when the plants are large enough and with some brown bark and with sufficient leaves not to be significantly damaged by herbicide if some leaf scorch should happen. The sprayers should also be skilled and careful.

Herbicides have different effects on cocoa (Brown and Boeting, 1972; Tan et al. 1972) and many are less safe to use in view of very serious damage which my be caused, in particular, by the translocated herbicides eg. the phenoxyacetic acids (2, 4-D and 2,4,5-T) and the halogenated aliphatic acids (dalapon, TCA) on accidental damage.

The literature eg. Wood (1975) cites several suitable herbicide mixtures for cocoa containing the above translocated herbicides and including ureas (eg. diuron and linuron) and the triazines (eg. atrazine and simazine) which are absorbed through the roots. It appears highly dangerous to use these mixtures in view of the potential damage which could be caused to the cocoa particularly in situations with low level skilled workers and supervision.

Paraquat is now commonly used because it is a contact herbicide and the safest due to its non-effect on brown bark. Its quick scorching action is useful in frequently wet situations. The main defect is that it is not very effective against Paspalum spp. and other established weeds so that frequent follow-up, spray rounds are required. In very open conditions and with frequent rains i.e. areas favourable to weed growth, significant regeneration is seen within 3 to 6 weeks. Frequent spray rounds are therefore required.

MSMA, another common contact herbicide, has been reported to cause leaf symptoms similar to zinc deficiency and avoidance of its use it generally advocated.

Glyphosphate is a highly effective herbicide against grasses and widely used against lallang and for control of persistent grasses in mature cocoa. There is no information on phytotoxicity in young cocoa.

Flauzifop-butyl which is highly effective against Paspalum spp. And reported to be safe in young cocoa is now being evaluated.

The commonly established shade trees eg. Gliricidia are also equally susceptible to the translocated herbicides.

In view of the above and the very limited range of suitably safe herbicides, the following recommendations are made :-

1. Preplanting : In absence of shade trees and cocoa, the most effective herbicides or herbicide mixtures may be used against the weeds present.

2. Establishment of shade trees : Strip or circle spraying of shade trees with Paraquat at 2-3 l/ha (1½ – 2 pts/ac.) rate depending on amount of light. Higher rates should be used in the open.

In inter-rows, the most effective herbicide mixtures may be used to eradicate the weeds and prepare the areas for cocoa planting but take care to avoid spray drift and contact with the shade trees.

As required, brush killers such as Garlon, and the translocated herbicides as 2,4-D amine alone or in mixtures with Paraquat and MSMA are used. Lallang, a common problem, may also be tackled with glyphosphate or dalapon.

3. Cocoa. Strip or circle spraying with Paraquat at 1.5/3 l/ha (1-2 pt/ac) rate chosen again depending on amount of light.

Persistent grasses may be tackled with glyphosphate spray in mature cocoa. Other persistent broad leaf weeds should be eradicated by hand or brushed/wiped with a brush killer such as Garlon where risk of contact with the cocoa is minimal.

The above recommendations commit the estate to frequent spraying rounds in the early stages of establishment but are probably justifiable in view of the limited period when spraying is required and the dangers posed by “something” going wrong.

In view of the frequent introduction of new herbicides, there is often temptation to try them. This is encouraged but managers should check on possible side effects from the suppliers and also not use widescale until certain that no harmful side effects are likely.

Herbicide application techniques

The 18 l knapsack sprayer is still commonly used. Advances in herbicide application techniques have been made and CDA sprayers using very low volumes have been widely tried in Malaysia recently. Also available now is the very low volume sprayer, the CP15 from Cooper-Pegler which has a pressure regulator and can possibly spray down to 20 t/ha, a significant reduction in water requirement.

The CDA sprayers are more efficient in usage of herbicides and particularly suitable for the translocated glyphosphate against lallang and other grasses. Reductions of chemical requirement by 1/2 to 2/3 have been claimed and the technique should be used in lallang blanket and spot spraying situations. The droplets are however more susceptible to drift and use in very exposed young immature cocoa may not be advisable.

As spray drift is to be avoided as far as possible, use of the correct nozzle with the conventional knapsack sprayer will help. Polijet tip nozzles from ICI to be used in conjunction with paraquat are given in Table 7.

Table 7 : ICI polijet nozzles

* Throughput at normal spraying pressure of 15 p.s.i.
** Swathe achieveable at nozzle height of 45 – 50 cm

The yellow polijet nozzle appears most suitable for use in young immature and young mature cocoa and spot spraying situations while the green polijet nozzle is probably best for mature cocoa.

Of course, good maintenance and calibration of the sprayers and nozzles is necessary to ensure good results as well as avoid damage by leaking pumps and misdirected sprays from damaged nozzles.

The use of spray shields to minimise danger of accidental drift especially in young cocoa is encouraged.

Proper safety precautions with the equipment and herbicides are advisable in view of the high toxicity of the principal herbicide used i.e. paraquat and all workers and staff involved should be made aware of the dangers of the chemicals used and precautions which are required including proper storage and labeling of herbicides, proper functioning and use of equipment, protective clothing and other gear as necessary, proper handling of the herbicides and washing up immediately after work.

Assessment of results

The weed control measures taken should be assessed for the following :-

• achievement of objective in terms of kill and area covered
• standard of spraying or weeding
• productivity of labour
• costs of control

Continuous evaluation of results achieved is essential not only because of the need to improve results all the time in good management practice but because spraying, weather and labour input conditions after very considerably and cause different results from expectation. Quick repeat spraying follow-up action may sometimes be required which will result in lower costs and better control of the weeds and growth of the cocoa in the long run.

Discussion

The answers to the possibilities posed at the beginning of the paper therefore are as follows:_

• there are very few weed research scientists in this country and they are busy working mainly on crops other than cocoa
• there are still some weed control problems in cocoa, in particular, limited range of safe herbicides to use and frequent repeated spraying required. However the problem is confined mainly to preplanting and the young immature and mature stages of the crop only, say a period of about 3-4 years mainly
• weed control is very important in young cocoa but probably not critical in most situations in mature cocoa
• herbicide usage is low in relation to other crops such as oil palm and rubber, taken over the life of a planting.

Conclusion

For good establishment of cocoa, regular weeding of the shade trees and cocoa seedlings planted is required. Competition from weeds is most severe in young immature cocoa but hand weeding for the first 6 to 9 months and monthly spraying with paraquat is adequate to control the weeds, provided perennial and woody weeds are eradicated before planting. After the cocoa canopies have closed over, weed competition is usually minimal. Overshading from shade trees planted should be avoided.

Delays in weed control in young immature cocoa should be avoided as far as possible and regular assessment of results and early remedial action will be highly advantageous to the cocoa plants.

Reference 
Ooi L.H. and Chew P.S. 1985. Some important agronomic and agricultural practices in cocoa  estates. TDMB Plantation Management Seminar, Kuala Trengganu

Note: The full list of references quoted in this article is available from the above paper.

Cocoa: Pruning

The growth of the cocoa tree has a distinct pattern and differs at different ages. This is illustrated diagrammatically in Fig. 3.

1-4, Stages of the growth of cacao, Theobroma cacao L., Storculiaceae, from Tropical America. -1, Seedling of cacao (copied from Dyant-Najad, 1968). -2, Seedling before the first branching, note the rhythmic branching. 3-, Formation of the first plaglotropic stages. 4-, Adult Cacao. 5-, Base of plaglotropic axes, and the mechanism of the relay in the growth in height, note the parenchymatous dome that terminates the caulomare of the trunk. 6-, Plan of a tier 3 m in diameter, note the articulated structure, the rhythmic growth, and the axillary position of the flowers.

After germination, the seedling grows in height with regular flushes of growth until about 1m to 2m high when upright growth is stopped.

4 to 5 lateral branches (fan branches) are then formed at the jorquette. After a phase of growth, the elongation of growth of the trunk recommences when a new chupon grows out of lateral bud below the jorquette. This new growth is usually vigorous, traverses the whorl of branches and gives rise to a new tier of branches 1m to 2m higher than the first tier or even higher if light is limiting.

If uncontrolled, the above pattern of upright growth can continue for 5 to 6 tiers growing to nearly 10 m high. To make the bushes easier to manage and also to improve yields, it is necessary to control the growth of cocoa by pruning it.

The subject on pruning has been discussed by many authors (Hardy, 1960; Cook, 1966; Chan, 1980 and Jelani et al. 1984)

Pruning requirements differ according to the age and stage of development of the trees and may be briefly described as initial pruning when the trees are establishing, shape pruning to develop a strong well-balanced framework of branches, maintenance pruning to be carried out to maintain a balance between vegetative vigour and fruit production and rejuvenation pruning when vigour and yield of the bushes drop as a result of disease or pest damage.

At all times, pruning should be for a definite purpose as it may be expected that excess removal of foliage will seriously delay growth in young trees and reduce yields in mature cocoa.

The major objectives of pruning are:-

• Height control
• To produce strong/well-balanced framework of branches
• To maintain balance between vegetative vigour/fruit production
• To rejuvenate disease/pest damage bushes
• To promote aeration
• To facilitate access

The above objectives could be achieved through various types of pruning tailored to specific need. The main types of pruning carried out in Malaysia are:-

• Height control pruning
• Number of fan branches pruning
• Water shoots pruning
• Periphery pruning
• Within canopy pruning
• Pest/disease pruning
• Rehabilitation/rejuvenation pruning

For practical reasons, it is necessary to restrict the growth of the cocoa bushes to a manageable height. In Malaysia, the standard practice is to restrict the growth of cocoa to one storey only. However, if the first storey is too low as to hinder field operations, a second storey is allowed to grow. The storey is removed eventually when the second storey is fully developed. Strong dominant branches that grow vertically upward on the fan branches are also removed to restrict height increment (height control pruning).

Some planters prefer to restrict the main fan branches arising from the jorquette to four only. Usually, there are 4-5 main fan branches when the cocoa branches at a jorquette and it is really not necessary to control the number of main fan branches unless they are not balance (number of fan branches pruning).

To cut down unnecessary growths and improve the usage of assimilates, all water shoots arising from the main trunk should be pruned regularly (monthly). It is important that water shoots are pruned at an early stage of growth. They should be pruned as close to the main trunk as possible. Unless they are pruned flush with the trunk, there is a tendency for numerous water shoots to grow from the base of the improperly pruned water shoots pruning could damage flower cushions and reduce fruiting (water shoots pruning).

Once the cocoa bushes are fairly well developed with self-shading canopy, all the low hanging/droopy branches within 1.00 m to 1.25 m from the ground should be pruned to facilitate access and to encourage more upright growths (perihphery pruning).

Finally, the within canopy/shape pruning is carried out produce an ideal bush growth form having the following characteristics:-

• Strong/well-balanced framework of branches
• Minimal unproductive branches i.e. slender/droopy branches with foliage receiving little/no direct sunlight and badly diseased/moribund branches.
• Foliage concentrating mainly close to canopy surface
• Well aerated canopy
• Minimal obstruction to access/harvesting

Once a desired growth form and canopy is achieved, maintenance pruning should be carried out regularly to maintain a balance between vegetative vigour and fruit production.

Sometimes it is necessary to rehabilitate/rejuvenate a mechanically damaged (eg. falling timber when the shade trees are poisoned) or disease damage bushes (eg. advance stage of VSD infection).

In such cases, a basal chupon near the collar region may be allowed to develop into a full bush to replace the damaged/diseased bushes. Budding of such bushes with high yielding clones have also been tried with satisfactory results.

For best results, pruning should be properly timed. The unwanted branches and water shoots should be pruned in their early stage of growths.

For shaping and maintenance pruning, pruning should be carried out before the main flushing and flowering seasons.

It is advisable to practice monthly or even more frequent water shoots pruning when required. The other types of pruning may be carried out at quarterly intervals.

Always maintain a continuous canopy. Never overprune or expose the jorquette.

Pruning to control VSD is a much debated and controversial subject in Malaysia and will be dealt with under pest and disease.

Reference 
Ooi L.H. and Chew P.S. 1985. Some important agronomic and agricultural practices in cocoa  estates. TDMB Plantation Management Seminar, Kuala Trengganu

Note: The full list of references quoted in this article is available from the above paper.

Cocoa: Shade Management Systems

The subject of shade management systems is a rather complex issue. A multitude of shade trees and combinations are possible. Usually a combination of permanent and temporary shade trees are planted to provide shade for cocoa. Common choices are:-

Temporary shade

Currently the preferred shade trees are coconut, Gliricidia, Leucaena and Cajanus.

The choice of a suitable shade system basically depends on the climatic factors (rainfall and soil moisture principally), soil fertility, adequacy of time for shade preparation, presence or absence of existing shade, sufficiency and efficiency of management inputs and objectives of the planting.

Shade management system and practices followed should be designed to :-

• to attain the shade levels required quickly and easily.
• adjust the shade levels to that required easily.
• maintain shade levels as long as required easily.
• not obstruct or hinder other management work in the area.
• allow for shade requirements of cocoa at maturity.

The key elements involved in choice of a shade management system are therefore:-

• time available.
• shade requirement of cocoa planting.
• shade requirement of cocoa at maturity.
• shade material availability.
• labour and management skills available.
• maintenance and management requirements of the shade.
• objectives of the planting i.e. cocoa mono-culture, cocoa/coconuts, etc..

Clean cleared systems

For a clean cleared system where fast growing shade trees have to be planted to provide shade for cocoa, it is usually necessary to plant the shade trees about a year ahead of cocoa. A combination of Gliricidia and Cajanus can provide adequate shade in 6-7 months (Wills, 1980). For the novices, however, it is prudent to plant the shade trees about a year ahead of cocoa to cater for adverse weather conditions and also for other unforeseen problems such as planting failures, pest and disease attach etc.

A shade management system for a cocoa-coconut intercropping system using Gliricidia as temporary shade and MAWA as minimum permanent shade is briefly outlined below as an example:-
Cocoa-coconut intercropping using Gliricidia as temporary shade and MAWA as minimum permanent shade

Planting schedule/pattern

Plant MAWA at 12m x 12m (69 palms/ha) and Gliricidia maculata at 1.5 m x 3.0 m (1800 trees/ha) about a year ahead of cocoa. Gliricidia should not be planted within 3 m from the coconuts. Cocoa at 3m x 3m (1042 trees/ha). The layout of the planting system is illustrated in Figure 2. Should Gliricidia grow poorly, supplementary shade trees such as Cajanus cajan should be planted in pockets at 1.5 m apart along the Gliricidia rows as a stop gap measure.

Gliricidia shade thinning

The above thinning schedule must be considered together with the shade levels suggested for cocoa in Table 4. Thinning should preferably be carried out during the early part of the wet season when the Gliricidia has refoliated.

Fig. 2 Cocoa/Coconut intercropping MAWA as minimum economic shade

Scale :_ 1cm : 3m

Note:- MAWA and Gliricidia planted one year ahead of cocoa

Under existing shade systems

Another category of planting system is to retain some of the existing shade trees as temporary shades such as planting cocoa under thinned jungle, old oil palm and old rubber trees. The retained temporary shade trees to be removed completely in stages as the cocoa matures and as the planted shade trees (usually a combination of MAWA, Gliricidia and Leucaena) could provide shade for cocoa.

Such system usually entails the adjustment of the existing shade to a suitable level prior to planting cocoa. Usually, as much big trees as possible are removed and the desired intermediate and permanent shade trees are planted prior to planting cocoa.

The main advantage of this system is that it obviates the need to establish temporary shade and hence saves time and probably initial expenditure. However, there is a major drawback in the system. The falling timber from the retained oil palm, jungle/rubber trees when they are poisoned can cause considerable damage to the under planted cocoa if too many big trees are retained. The amount of work and costs incurred in rehabilitating the damage cocoa and clearing/staking the fallen timber can be considerable. This is particularly true for planting under thinned jungle and old rubber.

An example of under thinned jungle system using Gliricidia/Leucaena as intermediate shade and MAWA as permanent shade is outlined below and overleaf in chronological order:-

Planting cocoa under thinned jungle using Gliricidia/Leucaena as intermediate shade and MAWA as final permanent shade

1. under-brushing
2. fell all jungle trees with diameter bigger than 15-20 cm
3. clean clear 120 cm wide rentices for planting cocoa and shade trees. Distance between rentices i.e. between cocoa rows at 3.5 m apart.
4. Selectively fell the bigger of the remaining jungle trees in areas where the jungle tree shade is still too dense.
5. Blanket spray the area
6. Plant a mixture of Gliricidia and Leucaena alternately at 3.5 m x 5.0 m (571 trees/ha)
7. Plant MAWA coconuts at 14m x 10m (71 palms/ha)
8. Plant cocoa at 3.5 m x 2.5 m (1142 bushes/ha)
9. Poison all the remaining jungle trees in stages within one year after the cocoa has been planted.
10. Poison all the intermediate shade gradually as the cocoa matures and when MAWA is able to provide shade for cocoa.

As for the other systems, shade thinning must be considered together with the shade requirements of cocoa outlined in Table 4.

Reference 
Ooi L.H. and Chew P.S. 1985. Some important agronomic and agricultural practices in cocoa estates. TDMB Plantation Management Seminar, Kuala Trengganu

Note: The full list of references quoted in this article is available from the above paper.

Cocoa: Shade and Light

Although cocoa seedlings can be grown in the absence of shade (Cunningham & Burridge, 1960; Lee & Garot, 1971; and Lee, 1978), in most cases, it is usually very difficult to achieve a satisfactory cocoa plantation in Malaysia under fully exposed condition.

Inadequate shade and subsequent moisture stress retards the growth of young cocoa. In extreme cases, 30-50% casualties have been reported. Over-exposure also results in cocoa jorquetting at very low heights thus impeding field access/operations. Another problem excessive light is increased attach by leaf eating insects, particularly cockchafer beetles. Over-exposure also creates problem in weed control.

Over the other hand, excessively shaded mature cocoa produces very poor yields.

The light requirement of cocoa has been extensively reviewed by Owusu (1978). Young cocoa plants grow best at about 30%-60% light, the light requirement of individual leaves on a plant for photosynthesis being met by 3-30% full sunlight.

Harun & Kamariah (1983) reported that for nursery seedlings, the optimal shade regime is 80% shade initially and gradually reduced to 55% shade from the 4^th month onwards.

Murray (1954) reported that best yield was achieved at 50% light without manuring and at 75% light with manuring in Trinidad. Khoo & Chew (1978) noted that the yield of the underplanted cocoa increased linearly with the rate of coconut thinning.

The requirements for light vary between environments and also with the age of the cocoa plants. In general, young cocoa plants require more shade than those with well developed and self-shading canopy. Cocoa grown on fertile soils located in areas with little moisture stress also requires less shade.

For good results, shade regimes must be adjusted to suit the stage of growth of cocoa, soil fertility as well as the environmental conditions.

A suggested shade regimes suitable for Malaysian conditions is given in Table 4.

Table 4 : Suggested % shade levels for cocoa

N.B. : These are expected theoretical % shade levels for best establishment, growth and yields under each condition. Practical considerations, in particular damage from retained initial overhead shadewhich is poisoned out after the first year, however make it necessary often to modify these levels. Other management practices are than implemented to offset the setback from the less than optional shade conditions.

Reference 
Ooi L.H. and Chew P.S. 1985. Some important agronomic and agricultural practices in cocoa estates. TDMB Plantation Management Seminar, Kuala Trengganu

Note: The full list of references quoted in this article is available from the above paper.

Cocoa: Planting Systems

In Malaysia numerous systems of planting cocoa have been tried. Growing cocoa under rubber, oil palm and coconuts have all been reported by various authors (Blencowe, 1967; McCulloch, 1967 and Ramadasan et. al. 1978). At conventional planting distances, rubber and oil palm are too competitive particularly for light to produce good cocoa yields.

However, satisfactory yields of both cocoa and oil palm can be achieved by intercropping cocoa with oil palm planted in wide avenues. (Lee & Hanafi, 1978)

The cocoa-coconut intercropping system has also changed. The days of high coconut stand intercropped with cocoa are past. Present emphasis is to plant more cocoa and use coconut as a minimum economic top shade. Some have gone to the extreme of planting monoculture cocoa. (Wills, 1980 and Basket et al., 1982).

Numerous other cocoa-coconut planting systems and patterns are also commonly practiced. The most common ones are MAWA planted regularly at 9m x 12m to 12m x 12m (69 to 92 palms/ha) as permanent top shade intercropped with cocoa at 3m x 3m (1019 to 1042 bushes/ha). Temporary shade such as Gliricidia maculata and Gajanus Cajun are planted together with MAWA about a year ahead of cocoa to provide initial shade. The temporary shade trees are gradually removed completely in stages as the MAWA matures.

More recently, planting of MAWA or oil palm in twin rows in wide avenues intercropped with cocoa has also been tried on experimental scales. The main advantage of this system is that field mechanization can be carried out with ease. Machinery and field workers can move along the wide paths in between the MAWA/oil palm twin rows without undue impediment.

The planting patterns are illustrated in figures 1 and table 3.

The main reason for intercropping cocoa with coconuts or oil palm is that such systems utilize the land more efficiently than the monocrop systems. Since mature cocoa requires some protective shade, it is logical that planting shade trees producing economic crops would improve the viability of a planting. However, they should not be too competitive, particularly for light. In this regard, coconut is superior to oil palm. From an agronomic point of view, an evenly spaced shade (eg. coconut at 12 m x 12 m) is better than shade trees planted in avenues (eg. intercropping systems listed in table 3). However, each system has its advantages and disadvantages and these must be tailored to suit one’s objectives.

Fig : 1 : MAWA/oil palm in twin rows in wide avenues intercropped with cocoa

Cocoa: Nursery Practices

Nursery practices should be geared to produce really well grown and vigorous seedlings free from major pests and diseases. There is really no substitutes for starting off with really well nursed planting materials. Cutting corners in the nursery such as overcrowding the seedlings to save space and planting out small undersized seedlings usually only ends up more costly in the fields. Small seedlings are more difficult to look after in the field. They cannot withstand adverse growing conditions as well as the well grown seedlings and also come into bearing much later. Longer immature period means higher cost and poorer cash flows.

Major nursery operations and the recommended practices are briefly outlined below:-

Ordering cocoa seeds

Seeds must be ordered well in advance from several reputable sources particularly where large plantings are involved.

Essentially, one must ensure that adequate quantities of the desired crosses are available for planting at the correct time.

The number of seeds that must be ordered depend on the planting density, expected losses in the nursery from non-germination, runts, poor growth, pests/disease damage and losses in the field after planting.

For example if	:-	the number of planting points	=	A,
		the number of non-germination	=	x %
		the number of nursery losses	=	y %
		the number of field losses	=	z %
The number of seeds that must be ordered

Under normal circumstances, about 40% extra seeds must be ordered to allow for non germination, nursery culling and supplying.

Nursery site/space/shade

Nursery site should be well drained, close to cheap sources of adequate and reliable water supply and good top soil (potting media) and to the area to be planted; well protected from animals and theft and within easy reach for supervision.

The allotted area should allow for spacing of polybags and also for drainage, paths and transport access. For good growth and to avoid etiolation, the seedlings should be spaced depending on the nursery period (Table 2).

Table 2 : Nursery spacing and polybag size

The ideal shade for nursery is one that can be adjusted to transmit the required amount of light for optimal growth. At sowing, the shade should be about 80%. The shade regime should be gradually reduced to about 50% at field planting, usually at 5-7 months.

Potting media/polybag filling

Only good top soil, preferably from the top 75 mm of soil should be used for filling the bags. The soil medium should allow good drainage and root growth and should not disintegrate when the bag is removed at transplanting. Recommended textures are sandy clay loam to clay loam.

If heavy clay has to be used, coarse river sand in the ratio of 1:4 should be added to improve drainage and aeration. A homogeneous mix may be achieved with the aid of a rotavator/cement mixer.

Basal fertilizers if recommended should be mixed thoroughly with the potting medium. This can be satisfactorily done in convenient heaps with the aid of a changkul/spade. However, it is important that the soil to fertilizer ratio should be correctly calibrated.

pH of soil, if not already known, should be checked and corrected to 5.5 to 6.5 unit.

Bag filling is more efficient if a hopper and funnel is used. Bag bottoms should be folded in so that bags sit better.

The soil should be allowed to settle in the bags before planting of seeds. However, bags should not be filled more than 2 to 3 weeks in advance of planting and should not be filled when the soil is wet.

The bags should be spaced out at the suggested spacings prior to planting. Spacing at a later stage is undesirable as the growth of cocoa seedlings are adversely affected if shifted. At the same time, double handling of large numbers of bags is labour intensive and expensive. Delay in spacing out is also not uncommon, resulting in etiolation of the seedlings. This is extremely undesirable. Etiolated seedlings are difficult to establish and grow poorly in the field. In extreme cases, the seedlings have to be supported to remain erect.

Planting seed

On receipt, the bags holding the seeds should be opened and spread out immediately by a responsible person for airing and checking.

This is important as cocoa seeds though properly processed and cleaned can still generate a fair amount of heat in transit. Excessive heat build up can kill the seeds.

Seeds may be planted as soon as they are received. Alternatively, they can be pregerminated prior to planting. The latter method is preferred if non-germination is expected to be high.

Deep planting should be avoided. As cocoa seed germination is epigeal, the cotyledons are pushed above the ground in the process of germination. Hence one should not attempt to cover up the seeds with soil as the cotyledons emerge from the soil during germination.

Watering

Watering is perhaps the most important single requirement in a polybag nursery. Adequate water should be supplied for good growth. However, over-watering especially in the first 2-3 months should be avoided as the young cocoa seedling is extremely sensitive to water-logging.

Watering once a day with ½ to ¾ litre of water per seedling is generally enough. However, the correct rates may be determined by checking the moisture content of the potting media. It should be moist at the top and bottom of the bag. Increase the rate if the soil is dry and withdraw/decrease the rate if it is too wet. During unusually long spells of dry weather, it may be necessary to water the seedlings twice a day.

An overhead sprinkler irrigation system if feasible is advantageous. Sprinkler output will determine the length of sprinkling. An equivalent of 6 mm rain/day is generally adequate. However, the rates should be checked by examining the moisture content of the potting media. Distribution of the sprinkler system should be regularly checked to ensure even watering.

Pests and Diseases

The most likely nursery pests are the leaf eaters, particularly cockchafers. Cockchafer damage is normally higher along the road sides and in the more open areas where there are less vegetative barriers. As even moderate loss of leaves can set back the growth of seedlings severely, appropriate control measures such as regular insecticide spraying or erecting vegetative barriers of fronds along the perimeter should be carried out.

Common nursery diseases are Phytophthora blight, Collectotrichum leaf disease and Vascular Streak Dieback. All the 3 diseases can cause considerable losses if not controlled in time. Disease monitoring and control is therefore important in the nursery. A combination of cultural practices (reducing inoculum/humidity and improving drainage) and fungicide spraying usually provide adequate control.

Manuring/records

Nutrient requirements by cocoa seedlings in the nursery stage are not high. Small quantities of balanced nutrient applications are generally adequate to ensure good growth. However, it is important to use good potting media mixed with rock phosphate. The pH of media should also be adjusted to 5.5 to 6.5 with calcium limestone if they are too acidic.

Reference 
Ooi L.H. and Chew P.S. 1985. Some important agronomic and agricultural practices in cocoa estates. TDMB Plantation Management Seminar, Kuala Trengganu

Note: The full list of references quoted in this article is available from the above paper.

Cocoa: Planting Materials

The importance of selecting the planting materials most suited one’s environment cannot be over emphasized.

Ideally, planting materials selected should be precocious, capable of sustained high yields, easy to manage, resistant to major pests and diseases and also highly adaptable. For obvious reasons, the crops should also be able to satisfy buyer quality specifications such as bean size, chocolate flavour etc.

Presently, there is insufficient information on environment-material interaction to allow for “environmat recommendation” as for rubber. However, a fair amount of data is available on the susceptibility/resistance of the hybrids to two major diseases in Malaysia i.e. Vascular Steak Dieback and Phytophthora palmivora . The latter is responsible for both black pod disease and canker in the field as well as seedling blight in the nursery.

Various authors reported that Sca6, Sca12, Pa35, Na32, Na33 and Amelonado are resistant to P. palmivora (Holliday, 1954: Spence & Bartley, 1966; Leather, 1966; and Gunawardena 1966).

Ang (1978) reported that progenies derived from Pa7 are more susceptible to VSD while those derived from Sca6 and Sca12 are most tolerant.

Ooi & Chew (1985) reported that Amelonado and crosses with Amelonado parentage are generally more susceptible to VSD.

Through the Malaysian Cocoa Growers Council (MCGC), the major cocoa growers imported 9 Keravat clones from Papua New Guinea in 1982. Most of the clones are resistant to VSD in PNG. Unfortunately, some of them are very susceptible to black pod disease under PNG growing conditions. The clones have been distributed to the interested parties and are now being evaluated in both the Pen. Malaysia and Sabah.

Therefore, in areas where VSD is a major problem, one should avoid planting Amelonado and its related crosses and also progenies derived from Pa7 clone. Materials selected for VSD resistance should be the preferred choice.

In areas where black pod/canker is a serious diseases, crosses with Sca6, Sca12, Pa35, Na32, Na33 and Amelonado should be the preferred choices. However, Sca6 and Sca12 crosses have been discarded by some planters on account of their lighter beans.

Another factor that must be taken into account is that the performance of a particular hybrid could vary considerably between locations. (Ooi & Chew 1985). It is therefore advisable to plant as many proven crosses of diverse parentage as possible (say 5 to 10) in any planting.

Another reason for planting in large number of diverse crosses is that a high percentage of them are self-incompatible. To ensure efficient pollination and high yields, it is necessary to plant them as mixed hybrids or in series of narrow blocks of 3-4 rows per hybrid. Planting of large blocks of a single hybrid should be avoided unless these are self-compatible. As a rule of thumb, the width of a block of a single hybrid should preferably be not more than 15 m.

A self incompatible hybrid/clone if planted in a large continuous block would result in poor pollination and hence poor yield. This is amply illustrated in Table 1 below:-

Table 1 : Effect of planting large blocks of self incompatible hybrids on the yield of cocoa

Source : Tan (1982)
Key : * UIT1 x Na32 in 72 continuous rows
UIT1 x Na33 in 51 continuous rows cocoa planted in
** Mixed hybrids
Cocoa planted in 1977

The yield of Fld. K where the pollination was poor was only about 24% of the mixed hybrids on average.

To save guard oneself and also to ensure quality of planting materials, all seeds should be purchased from reputable sources with a research backing.

Reference 
Ooi L.H. and Chew P.S. 1985. Some important agronomic and agricultural practices in cocoa estates. TDMB Plantation Management Seminar, Kuala Trengganu

Note: The full list of references quoted in this article is available from the above paper.