Remediation of Cocoa Soils in Ghana as a Route to more Sustainable Cocoa Production

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SummaryCocoa is grown extensively in West Africa, producing 75% of world production. Ghana is the second most important cocoa producing country, where cocoa production provides a livelihood for an estimated 800,000 smallholder farmers. One of the main challenges facing the cocoa sector in West Africa is long-term soil deterioration on cocoa farms because of the depletion of soil nutrients caused by poor farming practices. This has resulted in a shifting cultivation pattern, and migration of cocoa farmers into virgin forest areas which is clearly unsustainable. Measures to improve soil health would improve both on-farm yields and thus the livelihoods of smallholder cocoa farmers. Previous collaborative research between the University of Reading and the Cocoa Research Institute of Ghana (CRIG) has demonstrated that many cocoa farms are deficient in key soil nutrients but also that inorganic fertilisers are unaffordable for many farmers. Against this background, this project seeks to explore routes for soil improvement on cocoa farms through utilisation of on-farm waste products, thereby contributing to more sustainable crop production and thus maintenance of livelihoods of smallholder cocoa farmers.The project will explore the use of composted and pyrolysed (burning organic materials in the absence of oxygen to produce "biochar") farm waste as soil amendments to improve soil fertility and health on cocoa smallholdings. Experiments will be conducted on a network of cocoa farms, established in a previous project, to ascertain the impact of composted farm waste and biochar on the performance of established cocoa trees. This will be evaluated through changes in yield and assessments of plant health by measuring the presence of pests and diseases. Shade trials at CRIG will also be utilised to ascertain the impact of maintained overhead shade trees on soil micro and macro fauna. Complementary experiments will also be conducted in the greenhouses of CRIG on seedlings in pots to ascertain the impacts of different soil amendments on the performance of juvenile cocoa. These experiments will also assess whether the performance of plants subjected to drought is improved by cultivation on soils ameliorated with different composts. Furthermore, the greenhouse experiments will consider whether plants grown in soils ameliorated with different composts are less susceptible to attack by insect pests and by diseases. Additional pot experiments will be conducted at the University of Reading in which cocoa seedlings grown in different soil amendments will be subjected to different temperature regimes within growth cabinets.Analyses will be conducted on the properties of soils amended with composts. These will assess the extent to which cation exchange capacity and availability of nutrients are improved through composting and biochar production. The microbiology and macrofauna of compost amended soils will be compared with controls as a critical factor that impacts on nutrient availability to the crop.The cost: benefit ratio of using composts and biochar will be explored and communicated to farmers through farmer field schools in the latter stages of the project. These events will be conducted on farms on which the trials were conducted and composting methods/ pyrolysis methods will be demonstrated to farmers.A summary of our findings will be presented at an end of project workshop which will be held in Ghana and attended by key stakeholders in the cocoa production chain. Furthermore, we will produce a manual and video that will be used as tools by extension agents to take the technologies developed out to larger numbers of farmers