Executive summary
This literature review on mineral nutrition of cocoa was commissioned by the Scientific Committee of the Cocoa Fertiliser Initiative to address the following questions:
What knowledge is currently available about mineral nutrition of cocoa?
What are the current knowledge gaps?
What are the key areas for further research?
Poor yields Current average cocoa yields in West Africa are around 400 kg/ha although yields of 5,000 kg/ha are achievable. Given the expected increase in global cocoa demand, and the diminishing incomes of cocoa farmers, there is an urgent need to increase cocoa yields.
Potential cocoa yields are determined by location and crop specific characteristics, such as climate and the crops natural life cycle, under otherwise optimal conditions. However, the availability of water and nutrients may limit production, and yields may be further reduced by weeds, pests and diseases. The gap between the potential yield and actual yield may be decreased by addressing the limiting and reducing factors with yield increasing and yield protecting measures.
As soil nutrient content in many cocoa growing regions is poor, an obvious way to increase yields is to address the nutritional needs of cocoa through fertiliser. However, the response of cocoa trees to fertiliser will remain limited unless the crop is well managed and in a healthy condition.
Potentially strong yield response to fertiliser, but differences in response poorly understood There is a strong cycling of nutrients within cocoa systems and the amounts of nutrients removed through harvest are relatively small. Yet in the long term cocoa production leads to depletion of soil nutrients. Although the soils upon which cocoa in West Africa was established used to be fertile, many of them are no longer able to provide the nutrients required to obtain good yields.
Several trials have shown that cocoa productivity can be more than doubled when fertilisers are applied. However, there is large variability in yields and fertiliser response, and in some cases fertilisers show little effect. The effects of fertilisers depend on the cocoa tree requirements and current nutrient availability from the soil, but also on other environmental conditions, presence of pests and diseases, and the management of shade trees and pruning of cocoa.
Most cocoa researchers agree that the largest cocoa yields can be obtained in systems with little shade and high rates of fertilisers under good management, but that yields show a sharp decline after 10 years of full production. Under shade, cocoa yields respond less strongly to fertiliser, but the yield decline is also less severe…
Narrow research base Various lines of research related to mineral nutrition of cocoa have contributed to current understanding, including the establishment of nutrient balances in different cocoa production systems, pot experiments, and short and long term fertiliser field trials on experimental plots or existing farms. Much of the primary research was conducted over 40 years ago. Many variables have not been adequately measured and quantified and only few treatments were compared. Research has been conducted under a restricted range of environments and regions and often for only a few years, whereas the life span of the crop can be 40 years or more. Conclusions drawn from these studies may only be valid under the circumstances under which the research has been conducted. Nevertheless, these conclusions continue to be reused and extrapolated to the present day, for instance for the establishment of (fertiliser) recommendations.
Click to learn more >> Research Materials circa 2016