44 COFFEE/COCOA SCIENCE
At least 50 academic peer reviewed papers on coffee and coffee growing are published every month. Few of them get an audience beyond other academics. Dr Peter Baker looks at some recent scientific papers on aspects of the enduring problem of low cocoa productivity
Groeneveld JH, Tscharntke T, Moser G, Clough Y, (2010). Experimental evi- dence for stronger cacao yield limitation by pollination than by plant resources. Perspectives in Plant Ecology, Evolution & Systematics 12: 183–191.
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ollination is a hot topic, with increas- ing evidence that bee colonies are dying in ever greater numbers, lead-
ing some to call them agriculture’s ‘canary in the mine.’ In coffee too, evidence mounts that even for supposedly self-pollinating Arabica coffee, bees can increase yields. Time then to look at cocoa, in a new
paper from Göttingen University’s agro ecology group: the authors remind us that cocoa flowers (called cherelles) are dependent on cross-pollination (by midges, not bees) but only about 5 per cent of flow- ers ever develop into mature fruits. The cause of this high wastage is not
well understood; some say it is due to a lack of pollinators whereas other research contradicts this, blaming instead insufficient nutrients to support a larger number of flowers through to harvest. The authors painstakingly hand pollinat-
ed cocoa trees at natural and enhanced intensities (10 per cent, 40 per cent, 70 per cent and 100 per cent of flowers below 2m stem height). These pollination treatments were combined with different levels of nitro- gen fertilizer and experimentally controlled shade levels. The results revealed that pollination
intensity and the intensity of flowering are the main determinants of the number of mature pods and that fertilizers and other treatments did not materially affect yields. An increase in pollination from 10 per cent
What the papers say
Research by Göttingen University’s agro ecology group suggests more attention ought to be paid to cocoa pollination
farms have little or no shade and are not well maintained; two to three weedings and one or two insecticide applications per year was the norm. Fertilizers are seldom used and the average yields were low, ranging between 260kg and 560kg of beans/hectare.
Abankwah V, Aidoo R, Osei RK, (2010) Socio- Impact of Government Spraying Programme on Cocoa Farmers in Ghana. Journal of Sustainable Development in Africa. 12: No.4, 116-126.
to 40 per cent of flowers resulted in an extra 350g of dry beans per tree, which could mean an extra 350kg per hectare, roughly double current smallholder yields. Clearly this subject needs further study
because, if cocoa is so limited by pollina- tion, strenuous measures should be taken to improve conditions for the midges that provide this vital and entirely free service. Field studies linking midge abundance to
yield need to be done to validate this work; presumably midge populations boom under certain conditions but is this reflected in local yield increases? It is a surprising fact that the very start of the supply chain depends on a creature as humble as the midge, and surely something of a rebuke to a global industry that understands so little about it.
Assiri AA, Yoro GR, Deheuvels O, Kébé BI, Keli ZJ, Adiko A, Assa A, (2009). Les carac- téristiques agronomiques des vergers de cacaoyer (Theobroma cacao L.) en Côte d’Ivoire. Journal of Animal & Plant Sciences 2: 55- 66.
service. They surveyed 800 cocoa farmers in the three main production areas of Côte d’Ivoire and discovered that most of them were illiterate, with an average age of 49. 80 per cent were smallholders with less than 10 hectares. Over 60 per cent of plan- tations were between 11 and 30 years old. Cocoa farms are mainly established on cleared forest, by direct seeding of unse- lected plant nuts. 70-90 per cent of old
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he poor yield of cocoa farms is con- firmed by the authors of this paper that has just reached our abstract
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he impact of a government cocoa spraying programme on cocoa farm- ers in Ghana is assessed in this
paper. Nine years after implementing the project, the majority of farmers view the project as effective. However, despite this, the economic for-
tunes of cocoa farmers appear not to have improved much during that time because of a concomitant decline in farmers’ purchas- ing power. To help improve the efficiency of the programme, the authors make a num- ber of useful recommendations.
Asare, R. and David, S. 2010. Implementing guide for planting, replanting and tree diver- sification in cocoa systems. IITA, Ghana. Forest & Landscape Working Paper No. 46 pp120.
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duction in West Africa. It highlights the major efforts made at improving upon existing methods to control the disease. C&CI
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he objective of the guide is to improve farmers’ knowledge and skills to carry out the necessary best
practices in revamping old farms or start new ones and as such provides useful information for producing a more diversely planted cocoa farm.
Dzahini-Obiatey H, Domfeh O, Amoah FM, (2010). Over seventy years of a viral disease of cocoa in Ghana: From researchers’ per- spective. African Journal of Agricultural Research Vol. 5 (7): 476-485. Available online at
http://www.academicjournals.org/AJAR.
his paper reviews work on the control of cocoa swollen shoot virus disease, the most significant virus affecting pro-
May 2011 C&CI
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