Improving soil health and closing the yield gap of cocoa production in Ghana - A review

Ghana is the second largest producer of cocoa in the world and cocoa farming supports the livelihoods of 25-30% of Ghana's population. However, average yield is only about 30% of the potential yield. Cocoa farms established on recently cleared rainforest are initially productive, but then productivity declines as soils become depleted of nutrients. Further expansion of cultivated land by deforesting tropical rainforests is environmentally costly, socially unacceptable, and inherently unsustainable. Therefore, strategies are urgently required to maintain and restore the productivity of existing smallholder farms to close this yield gap and sustainably increase cocoa production to meet growing demand. In this narrative review we provide context to the issues and highlight recent advances that offer promising opportunities to restore the soil health of Ghana's cocoa farms and sustainably reduce the yield gap. The shade trees in traditional agroforestry farms help prolong productivity for longer by supporting soil ecological functions and this has sparked renewed interest in the establishment of sustainable agroforestry cocoa farms. The single rate and formulation of mineral fertiliser recommended to farmers nationwide fails to account for variability in the response of different soil types to inputs. Therefore, site-specific fertiliser recommendations that also quantify the benefits of organic amendments are emerging. Composting and returning cocoa pod husks to the soil offers a considerable opportunity to close nutrient cycles (particularly for P and K) on cocoa farms and to help build and maintain soil organic matter. However, research is required to overcome the risk that recycling cocoa pod husks may contribute to the spread of black pod disease. Soil health indicators that quantify the soil ecological functions provided by these sustainable land management practices require benchmarking to monitor the impact of these interventions. (C) 2021The Author(s). Published by Elsevier B.V. on behalf of African Institute of Mathematical Sciences / Next Einstein Initiative.