Hostname: page-component-cd9895bd7-jkksz Total loading time: 0 Render date: 2024-12-22T21:39:27.092Z Has data issue: false hasContentIssue false
  • English
  • Français

THE WATER RELATIONS AND IRRIGATION REQUIREMENTS OF COCOA (THEOBROMA CACAO L.): A REVIEW

Published online by Cambridge University Press:  27 May 2011

M. K. V. CARR  and
G. LOCKWOOD
M. K. V. CARR*
Affiliation:
Emeritus Professor, School of Applied Sciences, Cranfield University, Bedford, MK45 0AL, UK
G. LOCKWOOD
Affiliation:
30 St. Martins Drive, Eynsford, Dartford, Kent, DA4 0EX, UK
*
‡Address for correspondence: Pear Tree Cottage, Frog Lane, Ilmington, Shipston on Stour, Warwickshire, CV36 4LQ, UK. Email: [email protected]
Get access Rights & Permissions [Opens in a new window]

Summary

The results of research into the water relations of cocoa are reviewed in the context of drought mitigation and irrigation need. Background information on the centres of production of the cocoa tree, and the role of water in crop development and growth processes, is followed by reviews of the effects of water stress on stomatal conductance, leaf water status and gas exchange, together with drought tolerance, crop water use and water productivity. Leaf and shoot growth occur in a series of flushes, which are synchronized by the start of the rains following a dry season (or an increase in temperature), alternating with periods of ‘dormancy’. Flowering is inhibited by water stress but synchronous flowering occurs soon after the dry season ends. Roots too grow in a rhythmic pattern similar to that of leaf flushes. Roots can reach depths of 1.5–2.0 m, but with a mass of roots in the top 0.2–0.4 m, and spread laterally >5 m from the stem. Stomata open in low light intensities and remain fully open in full sunlight in well-watered plants. Partial stomatal closure begins at a leaf water potential of about −1.5 MPa. Stomatal conductance is sensitive to dry air, declining as the saturation deficit increases from about 1.0 up to 3.5 kPa. Net photosynthesis and transpiration both consequently decline over a similar range of values. Little has been published on the actual water use of cocoa in the field. Measured ETc values equate to <2 mm d−1 only, whereas computed ETc rates of 3–6 mm d−1 in the rains and <2 mm d−1 in the dry season have also been reported. Despite its sensitivity to water stress, there is too a paucity of reliable, field-based published data of practical value on the yield responses of cocoa to drought or to irrigation. With the threat of climate change leading to less, or more erratic, rainfall in the tropics, uncertainty in yield forecasting as a result of water stress will increase. Social, technical and economic issues influencing the research agenda are discussed.

Type
Research Article
Information
Experimental Agriculture , Volume 47 , Issue 4 , October 2011 , pp. 653 - 676
Copyright
Copyright © Cambridge University Press 2011

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Acheampong, K. (2010). A physiological study on field establishment of cacao clones through the improvement of agro-ecological conditions. PhD thesis, University of Reading, UK.Google Scholar
Acheampong, K., Daymond, A. J. and Hadley, P. (2009). The physiological basis of the shade requirement of young clonal cocoa. Paper presented at the International Cocoa Research Conference, Bali, November 2009.Google Scholar
Ali, F. M. (1969). Effects of rainfall on yield of cocoa in Ghana. Experimental Agriculture 5:209–213.CrossRefGoogle Scholar
Allen, R. G., Pereira, L. S., Raes, D. and Smith, M. (1998). Crop evapotranspiration: guidelines for computing crop water requirements. Food and Agricultural Organisation of the United Nations, Irrigation and Drainage Paper 56, Rome, Italy.Google Scholar
Almeida, A-A. F. de, Brito, R. C. T., Aguilar, M. A. G. and Valle, R. R. (2001). Some water relations aspects of Theobroma cacao clones. In Proceedings 13thInternational Cocoa Research Conference, Kota Kinabalu, Malaysia, October 2000, 349–363.Google Scholar
Almeida, A-A. F. de and Valle, R. R. (2007). Ecophysiology of the cacao tree. Brazilian Journal of Plant Physiology 19:425–448.CrossRefGoogle Scholar
Alvim, P. de T. (1958). Stomatal opening as a practical indicator of moisture deficiency in cacao. In Séptima Conferencia Interamericana de Cacao, Palmira, Colombia, July 1958, 283–293.Google Scholar
Alvim, P. de T. (1977). Cacao. In Ecophysiology of Tropical Crops, 279–313 (Ed. Kozlowski, T. T.). London, Academic Press.CrossRefGoogle Scholar
Alvim, R. and Alvim, P. de T. (1977). Hydroperiodicity in cocoa tree. In Proceedings of the 5th International Cocoa Research Conference, Ibadan, Nigeria, September 1975, 204–209.Google Scholar
Alvim, P. de T. (1988). Relaçôes entre fatores climaticos e produçăo do cacaueiro. In Proceedings of the 10th International Cocoa Research Conference, Santa Domingo, Dominican Republic, May 1987, 159–167.Google Scholar
Anim-Kwapong, G. J. and Frimpong, E. B. (2006). Vulnerability of agriculture to climate change – impact of climate change on cocoa production. In Report on Vulnerability and Adaptation Assessment under the Netherlands Climate Change Studies Assistance Programme Phase 2. Cocoa Research Institute of Ghana.Google Scholar
Bae, H., Kim, S-H., Kim, M. S., Sicher, R. C., Lary, D., Strem, M. D., Natarajan, S. and Bailey, B. A. (2008). The drought response of Theobroma cacao (cacao) and the regulation of genes involved in polyamine biosynthesis by drought and other stresses. Plant Physiology and Biochemistry 46:174–188.CrossRefGoogle ScholarPubMed
Bae, H., Sicher, R. C., Kim, M. S., Kim, S-H., Strem, M. D., Melnick, R. L. and Bailey, B. A. (2009). The beneficial endophyte Trichoderma hamatum isolate DIS219b promotes growth and delays the onset of the drought response in Theobroma cacao. Journal of Experimental Botany 60:3279–3296.CrossRefGoogle ScholarPubMed
Balasimha, D. (1999). Stress physiology of cocoa. Journal of Plantation Crops 27:1–8.Google Scholar
Balasimha, D., Anil Kumar, V., Viraktamath, B. C. and Ananda, K. S. (1999). Leaf water potential and stomatal resistance in cocoa hybrids and parents. Plantations, Recherche, Developpement 6:116–118.Google Scholar
Balasimha, D. and Daniel, E. V. (1988). A screening method for drought tolerance in cocoa. Current Science 57:395.Google Scholar
Balasimha, D., Daniel, E. V. and Bhat, P. G. (1991). Influence of environmental factors on photosynthesis in cocoa trees. Agricultural and Forest Meteorology 55:15–21.CrossRefGoogle Scholar
Balasimha, D., Rajagopal, V., Daniel, E. V., Nair, R. V. and Bhagavan, S. (1988). Comparative drought tolerance of cacao accessions. Tropical Agriculture (Trinidad) 65:271–274.Google Scholar
Balasimha, D., Subramonan, N. and Chenchu Subbaiah, C. (1985). Leaf characteristics in cocoa (Theobroma cacao L.) accessions. Café Cacao Thé 29:95–98.Google Scholar
Baligar, V. C., Bunce, J. A., Machado, R. C. R. and Elson, M. K. (2008). Photosynthetic photon flux density, carbon dioxide concentration, and vapour pressure deficit effects on photosynthesis in cacao seedlings. Photosynthetica 46:216–221.CrossRefGoogle Scholar
Beer, J. (1987). Advantages, disadvantages and desirable characteristics of shade trees for coffee, cacao and tea. Agroforestry Systems 5:3–13.CrossRefGoogle Scholar
Braudeau, J. (1969). Le Cacaoyer. G-P Maisonneuve et Larose, Paris.Google Scholar
Bridgland, L. A. (1953). Study of the relationship between cacao yield and rainfall. The Papua and New Guinea Agricultural Gazette 8:7–14.Google Scholar
Burle, L. (1961). Le Cacaoyer. G.-P. Maisonneuve et Larose. France, Paris.Google Scholar
Carr, M. K. V. (2001). The water relations and irrigation requirements of coffee. Experimental Agriculture 37:1–36.CrossRefGoogle Scholar
Carr, M. K. V. (2009). The water relations and irrigation requirements of banana (Musa spp.). Experimental Agriculture 45:333–371.CrossRefGoogle Scholar
Carr, M. K. V. (2010a). The role of water in the growth of the tea (Camellia sinensis L.) crop: a synthesis of research in eastern Africa. 1. Plant water relations. Experimental Agriculture 46:327–349.CrossRefGoogle Scholar
Carr, M. K. V. (2010b). The role of water in the growth of the tea (Camellia sinensis L.) crop: a synthesis of research in eastern Africa. 2. Water productivity. Experimental Agriculture 46:351–379.CrossRefGoogle Scholar
Carr, M. K. V. (2011). The water relations and irrigation requirements of coconut (Cocos nucifera L.): a review. Experimental Agriculture 47:1–25.CrossRefGoogle Scholar
Carr, M. K. V. and Knox, J. W. (2011). The water relations and irrigation requirements of sugar cane (Saccharum officinarum L.): a review. Experimental Agriculture 47:27–51.CrossRefGoogle Scholar
Cheesman, E. E. (1944). Notes on the nomenclature, classification and possible relationships of cacao populations. Tropical Agriculture (Trinidad) 21:144–159.Google Scholar
Colas, H., Mouchet, S., Rey, H. and Kitu, W. T. (1999). Une approche du comportement hybrique du cacaoyer (Theobroma cacao L.) par des mesures de flux de seve brute: comparison entre une culture pure et une culture associee sous cocotier (Cocos nucifera L.). In Proceedings of the 12th International Cocoa Research Conference, Salvador, Bahia, Brazil, November 1996, 637–644.Google Scholar
Corley, R. H. V. (1983). Potential productivity of tropical perennial crops. Experimental Agriculture 19:217–237.CrossRefGoogle Scholar
CPCRI (2010). Central Plantation Crops Research Institute, Kerala, India http://cpcri.gov.in/garden%20management-cocoa.htmGoogle Scholar
Daymond, A. J. and Hadley, P. (2004). The effects of temperature and light integral on early vegetative growth and chlorophyll fluorescence of four contrasting genotypes of cacao (Theobroma cacao). Annals of Applied Biology 145:257–262.CrossRefGoogle Scholar
Daymond, A. J. and Hadley, P. (2008). Differential effects of temperature on fruit development and bean quality of contrasting genotypes of cacao (Theobroma cacao). Annals of Applied Biology 153:175–185.CrossRefGoogle Scholar
Daymond, A. J., Hadley, P., Machado, R. C. R. and Ng, E. (2002a). Canopy characteristics of contrasting clones of cocoa (Theobroma cacao). Experimental Agriculture 38:359–367.CrossRefGoogle Scholar
Daymond, A. J., Hadley, P., Machado, R. C. R. and Ng, E. (2002b). Genetic variability in partitioning to the yield component of cacao (Theobroma cacao L.). HortScience 37:799–801.CrossRefGoogle Scholar
Daymond, A. J., Tricker, P. J. and Hadley, P. (2009). Genotypic variation in photosynthetic and leaf traits in cocoa. Paper presented at the International Cocoa Research Conference, Bali, November 2009.Google Scholar
Diczbalis, Y., Lemin, C., Richards, N. and Wicks, C. (2010). Producing Cocoa in Northern Australia. Australian Government, Rural Industries Research and Development Corporation Report 09/092.Google Scholar
Dunlop, W. R. (1925). Rainfall correlations in Trinidad. Nature (London) 115:192–193.CrossRefGoogle Scholar
Edwards, D. F. (1973). Pollination studies on Upper Amazon cocoa clones in Ghana in relation to the production of hybrid seed. Journal of Horticultural Science 48:247–259.CrossRefGoogle Scholar
Edwin, J. and Masters, W. A. (2005).Genetic improvement and cocoa yields in Ghana. Experimental Agriculture 41:491–503.CrossRefGoogle Scholar
FAO (2010). http://faostat.fao.org/site/339/default.aspxGoogle Scholar
Fordham, R. (1972). The water relations of cacao. In Proceedings of the IV International Cocoa Research Conference, St. Augustine, Trinidad, January 1972, 320–325.Google Scholar
Gomes, A. R. S. and Kozlowski, T. T. (1988). Stomatal characteristics, leaf waxes, and transpiration rates of Theobroma cacao and Hevea brasiliensis seedlings.Annals of Botany 61:425–432.CrossRefGoogle Scholar
Gomes, A. R. S. and Kozlowski, T. T. (1989). Responses of seedlings of two varieties of Theobroma cacao to wind. Tropical Agriculture (Trinidad) 66:137–141.Google Scholar
Greathouse, D. C., Laetsch, W. M. and Phinney, B. O. (1971). The shoot growth rhythm of a tropical tree, Theobroma cacao. Australian Journal of Botany 58:281–286.Google Scholar
Greenwood, M. and Posnette, A. F. (1950). The growth flushes of cacao. Journal of Horticultural Science 25:164–174.CrossRefGoogle Scholar
Hadley, P., End, M., Taylor, S. J. and Pettipher, G. L. (1994). Environmental regulation of vegetative and reproductive growth in cocoa grown in controlled glasshouse conditions. In Proceedings of the International Cocoa Conference: Challenges in the 90s. Kuala Lumpur, Malaysia, September 1991, 319–331.Google Scholar
Hadley, P. and Yapp, J. H. H. (1993). Measurement of physiological parameters with respect to yield. In Proceedings International Workshop on Conservation and Utilization of Cocoa Genetic Resources in the 21st Century. The Cocoa Research Unit, University of the West Indies, Trinidad September 1992, 121–138.Google Scholar
Hardwick, K., Machado, R. C. R., Smith, J. and Veltkamp, C. J. (1988a). Apical bud activity in cocoa. In Proceedings of the 9th International Cocoa Research Conference, Lomé, Togo, February 1984, 153–158.Google Scholar
Hardwick, K., Robinson, A. W. and Collin, H. A. (1988b). Plant water status and the control of leaf production in cocoa. In Proceedings of the 9th International Cocoa Research Conference, Lomé, Togo, February 1984, 111–116.Google Scholar
Hardy, F. (1958). The effects of air temperature on growth and production in cacao. Cacao 3:1–15.Google Scholar
Hernandez, A. P., Cock, J. H. and El-Sharkawy, M. A. (1989). The responses of leaf gas exchange and stomatal conductance to air humidity in shade-grown coffee, tea and cacao plants as compared with sunflower. Revista Brasileira de Fisiologia Vegetal 1:155–161.Google Scholar
Huan, L. K., Yee, H. C. and Wood, B. J. (1986). Irrigation of cocoa on coastal soils in Peninsular Malaysia. In Cocoa and Coconuts: Progress and Outlook, Kuala Lumpur, Incorporated Society of Planters, 117–132.Google Scholar
Hutcheon, W. V. (1977a). Growth and photosynthesis of cocoa in relation to environmental and internal factors. In Proceedings of the 5th International Cocoa Research Conference, Ibadan, Nigeria, September 1975, 222–232.Google Scholar
Hutcheon, W. V. (1977b). Water relations and other factors regulating the seasonal periodicity and productivity of cocoa in Ghana. In Proceedings of the 5th International Cocoa Research Conference, Ibadan, Nigeria, September 1975, 233–244.Google Scholar
Hutcheon, W. V. (1981a). Physiological studies of cocoa (Theobroma cacao) in Ghana. PhD thesis, University of Aberdeen, UKGoogle Scholar
Hutcheon, W. V. (1981b). The Cocoa Swollen Shoot Research Project at the Cocoa Research Institute, Tafo Ghana. 1969–78.Technical Report Volume III, Section 5 Physiology Studies, 11–35. A joint research project funded by the Overseas Development Administration, London, UK and the Ministry of Cocoa Affairs, Accra, Ghana.Google Scholar
Hutcheon, W. V., Smith, R. W. and Asomaning, E. J. A. (1973). Effect of irrigation on the yield and physiological behaviour of mature Amelonado cocoa in Ghana. Tropical Agriculture (Trinidad) 50 (4):261–272.Google Scholar
ICCO (2010). Quarterly Bulletin of Cocoa Statistics XXXVI No 2 (Cocoa Year 2009/10). International Cocoa Organisation.Google Scholar
Jadin, P., Chauchard, A. and Bois, J. F. (1976). Alimentation hydrique des jeunes cacaoyers influence de l'irrigation. Café Cacao Thé 20:173–199.Google Scholar
Jadin, P. and Jacquemart, J-P. (1978). Effet de l'irrigation sur la précocité des jeunes cacaoyers. Café Cacao Thé 22:31–35.Google Scholar
Jadin, P. and Snoeck, J. (1981). Evolution du stock d'eau sous une cacaoyere – relation avec le climat. In Proceedings of the 8th International Cocoa Research Conference, Cartagena, Colombia, October 1981, 127–135.Google Scholar
Joly, R. J. (1988). Physiological adaptations for maintaining photosynthesis under water stress in cacao. In Proceedings of the 10th International Cocoa Conference, Santo Domingo, Dominican Republic, May 1987, 199–203.Google Scholar
Joly, R. J. and Hahn, D. T. (1989). Net CO2 assimilation of cacao seedlings during periods of plant water deficit. Photosynthesis Research 21:151–159.CrossRefGoogle ScholarPubMed
Köhler, M., Schwendenmann, L. and Hölscher, D. (2010). Throughfall reduction in a cacao agroforest: tree water use and soil water budgeting. Agricultural and Forest Meteorology 150:1079–1089.CrossRefGoogle Scholar
Kummerow, J., Kummerow, A. and Alvim, P. de T. (1981). Root biomass in a mature cacao (Theobroma cacao L.) plantation. Révista Theobroma 12:77–85.Google Scholar
Lee, G. R. (1975). Irrigated Upper Amazon cacao in the Lower Shire Valley of Malawi. II-A water rates trial. Tropical Agriculture (Trinidad) 52:179–182.Google Scholar
Lockwood, G. and Boamah Adomako, K. (2011). A review of cocoa clone trials in Ghana. Experimental Agriculture (in preparation).Google Scholar
Lockwood, G. and Pang, J. T. Y. (1996).Yields of cocoa clones in response to planting density in Malaysia. Experimental Agriculture 32:41–47.CrossRefGoogle Scholar
Maidment, W.T.O. (1928). Correlation between rainfall and cacao yields in the Gold Coast with special reference to effect of April rains on the following cacao crop. Department of Agriculture Gold Coast Year–Book, 1927, Bulletin 13:83–91.Google Scholar
McCreary, C. W. R., McDonald, J. A., Muldoon, V. I. and Hardy, F. (1943). The root system of cacao: results of some preliminary investigations in Trinidad. Tropical Agriculture (Trinidad) 20:207–220.Google Scholar
McKelvie, A. D. (1956). Cherelle wilt of cacao. I. Pod development and its relation to wilt. Journal of Experimental Botany 7:252–263.CrossRefGoogle Scholar
Miyaji, K-I., da Silva, W. S. and Alvim, P. de T. (1997). Productivity of leaves of a tropical tree, Theobroma cacao, grown under shade, in relation to leaf age and light conditions within the canopy. New Phytologist 137:463–472.CrossRefGoogle ScholarPubMed
Moser, G., Leuschner, C., Hertel, D., Hölscher, D., Köhler, M., Leitner, D., Michalzik, B., Prihastanti, E., Tjitrosemito, S. and Schwendenmann, L. (2010). Response of cocoa trees (Theobroma cacao) to a 13-month desiccation period in Sulawesi, Indonesia. Agroforestry Systems 79:171–187.CrossRefGoogle Scholar
Motamayor, J. C., Lachenaud, P., de Silva e Mota, J. W., Loor, R., Kuhn, D. N., Brown, J. S. and Schnell, R. J. (2008). Geographic and genetic population differentiation of the Amazonian chocolate tree (Theobroma cacao L.). PLoS ONE 3(10): e3311.doi:10.1371/journal.pone.0003311.CrossRefGoogle Scholar
Murray, D. B. (1961). Soil moisture and cropping cycles in cacao. In A Report on Cacao Research 1959–1960. Imperial College of Tropical Agriculture, Trinidad, St. Augustine, 18–22.Google Scholar
Niemenak, N., Cilas, C., Rohsius, C., Bleiholder, H., Meier, U. and Lieberei, R. (2009). Phenological growth stages of cacao plants (Theobroma sp.): codification and description according to the BBCH scale. Annals of Applied Biology 156:13–24.CrossRefGoogle Scholar
Obiri, B. D., Bright, G. A., McDonald, M. A., Anglaaere, L. C. N. and Cobbina, J. (2007). Financial analysis of shaded cocoa in Ghana. Agroforestry Systems 71:139–149.CrossRefGoogle Scholar
Orchard, J. E. (1985). The effect of the dry season on the water status of T. cacao in Ecuador. In Proceedings of the 9th International Cocoa Research Conference, Lomé, Togo, February 1984, 103–109.Google Scholar
Orchard, J. E. and Saltos, M. (1988). The growth and water status of cacao during its first year of establishment under different methods of soil water management. In Proceedings of the 10th International Cocoa Conference, Santo Domingo, Dominican Republic, May 1987, 193–198.Google Scholar
Owusu, K. and Waylen, P. (2009). Trends in spatial-temporal variability in annual rainfall in Ghana (1951–2000). Weather 64:115–120.CrossRefGoogle Scholar
Pang, J. T. Y. (2006). Yield efficiency in progeny trials with cocoa. Experimental Agriculture 42:289–299.CrossRefGoogle Scholar
Premachandra, G. S. and Joly, R. J. (1994). Leaf water relations, net CO2 assimilation, stomatal conductance and osmotic concentration as affected by water deficit in cacao seedlings. In Proceedings of the International Cocoa Conference: Challenges in the 90s. Kuala Lumpur, Malaysia, September 1991, 351–359.Google Scholar
Purseglove, J. W. (1968). Tropical Crops: Dicotyledons. London: Longman.Google Scholar
Rada, F., Jaimez, R. E., Garcia-Núňez, C., Azócar, A. and Ramirez, M. E. (2005). Water relations and gas exchange in Theobroma cacao var. Guasare under periods of water deficit. Revista de la Facultad de Agronomia 22:112–120.Google Scholar
Radersma, S. and Ridder, N. de (1996). Computed evapotranspiration of annual and perennial crops at different temporal and spatial scales using published parameter values. Agricultural Water Management 31:17–34.CrossRefGoogle Scholar
Raja Harun, R. M. and Hardwick, K. (1988). The effect of different temperature and vapour pressure deficits on photosynthesis and transpiration of cocoa leaves. In Proceedings of the 10th International Cocoa Conference, Santo Domingo, Dominican Republic, May 1987, 211–214.Google Scholar
Razi, M. I., Halim, A. H., Kamariah, D. and Noh, M. J. (1992). Growth, plant water relations and photosynthesis rates of young Theobroma cacao as influenced by water stress. Pertanika 15:93–98.Google Scholar
Ruf, F. (1995). From forest rents to tree-capital: basic “laws” of cocoa supply. In Cocoa Cycles: The Economies of Cocoa Supply, 1–53 (Eds F. Ruf and P.S. Siswoputranto). Cambridge, Woodhead Publishing Ltd.Google Scholar
Sale, P. J. M. (1970a). Growth, flowering and fruiting of cacao under controlled soil moisture conditions. Journal of Horticultural Science 45:99–118.CrossRefGoogle Scholar
Sale, P. J. M. (1970b). Growth and flowering of cacao under controlled atmospheric relative humidities. Journal of Horticultural Science 45:129–132.Google Scholar
Simmonds, N. W. (1998). Tropical crops and their improvement. In Agriculture in the Tropics 3rd edition, 257–293 (Eds Webster, C. C. and Wilson, P. N.). Oxford, Blackwell Science.Google Scholar
Skidmore, C. L. (1929). Indications of existing correlation between the rainfall and the number of pods harvested at Aburi and Asuansi.Department of Agriculture Gold Coast Year–Book, 1928, Bulletin 16:114–120.Google Scholar
Sleigh, P. A., Hardwick, K. and Collin, H. A. (1981). A study of growth periodicity in cocoa seedlings, with particular emphasis on the root system. Café Cacao Thé 25:169–172.Google Scholar
Smith, R. W. (1964). The establishment of cocoa under different soil moisture regimes. Empire Journal of Experimental Agriculture 32:249–256.Google Scholar
Taylor, S. J. and Hadley, P. (1988). Relationships between root and shoot growth in cocoa (Theobroma cacao L.) grown under different shade regimes. In Proceedings of the 10th International Cocoa Research Conference, Santa Domingo, Dominican Republic, May 1987, 177–183.Google Scholar
Teoh, K. C., Chan, K. S. and Chew, P. S. (1986). Dry matter and nutrient composition in hybrid coconuts (MAWA) and cocoa on coastal clay soils. In Proceedings of the International Conference on Cocoa and Coconuts: Progress and Outlook. Kuala Lumpur, Malaysia, October 1984, 819–835.Google Scholar
Thong, K. C. and Ng, W. L. (1980). Growth and nutrients composition of monocrop cocoa plants on inland Malaysian soils. In Proceedings of the International Conference on Cocoa and Coconuts 1978. Kuala Lumpur, Malaysia, 262–286.Google Scholar
Toxopeus, H. (1985). Botany, types and populations. Chapter 2 in Cocoa 4th Edition (Eds. Wood, G. A. R. and Lass, R. A.). Oxford, Blackwell Science, 17–18.Google Scholar
Toxopeus, H. and Wessel, M. (1970). Studies on pod and bean values of Theobroma cacao L. in Nigeria. 1. Environmental effects on West African Amelonado with particular attention to annual rainfall distribution. Netherlands Journal of Agricultural Science 18:132–139.CrossRefGoogle Scholar
van Himme, M. (1959). Étude de système radiculaire du cacaoyer. Bulletin Agriculture du Congo Belge et du Rwanda-Urundi 50:1541–1600.Google Scholar
Vogel, M. (1975). Recherche du déterminisme du rhythme de croissance du cacaoyer. Café Cacao Thé 19:265–290.Google Scholar
Wood, G. A. R. (1985a). Environment. Chapter 3 in Cocoa 4th Edition (Eds Wood, G. A. R. and Lass, R. A.). Oxford, Blackwell Science, 38–79.Google Scholar
Wood, G. A. R. (1985b). From harvest to store. In Cocoa 4th Edition, 444–504 (Eds. Wood, G. A. R. and Lass, R. A.). Oxford, Blackwell Science.Google Scholar
Wood, G. A. R. (1985c). Establishment. In Cocoa 4th Edition, 119–165 (Eds. Wood, G. A. R. and Lass, R. A.). Oxford, Blackwell Science.Google Scholar
World Cocoa Foundation (2010). http://www.worldcocoafoundation.org/learn-about-cocoa/cocoa-facts-and-figures.htmlGoogle Scholar
Yapp, J. H. H. and Hadley, P. (1994). Inter-relationships between canopy architecture, light interception, vigour and yield in cocoa: implications for improving production efficiency. In Proceedings of the International Cocoa Conference: Challenges in the 90s. Kuala Lumpur, Malaysia, September 1991, 332–350.Google Scholar
Yegappan, T. M. and Mainstone, B. J. (1981). Comparisons between press and pressure chamber techniques for measuring leaf water potential. Experimental Agriculture 17:75–84.CrossRefGoogle Scholar
Zuidema, P. A., Leffelaar, P. A., Gerritsma, W., Mommer, L. and Anten, N. P. R. (2005). A physiological production model for cocoa (Theobroma cacao): model presentation, validation and application. Agricultural Systems 84:195–225.CrossRefGoogle Scholar