The end of the first cocoa shade and manurial experiment at the Cocoa Research Institute of Ghana

SummaryIn an Amelonado cocoa (Theobroma cacao L.) shade and manurial trial, no-shade trees yielded three times as much as shaded trees over 17 years of continuous cropping, but it is inferred that the economic life of an unshaded Amelonado cocoa farm in Ghana may not last for more than 10 years of intensive cropping. No-shade trees require more fertilizer than shaded ones, and lack of fertilizers, especially P, will cause a decline in yield in less than 10 years. A mean loss of over 50% of organic carbon within 15 years, with the apparent organic carbon decomposition constant (Kc) = 4.67, was used as a measure of deterioration of the soil productivity. Deterioration of cocoa was rapid under the no-shade conditions partly because of the high loss of exchangeable bases and the greater stress caused by the higher yield. Trees under stress tended to become more susceptible to insect pests and probably to diseases. Shade conditions alfected the distribution of the . insect pests of cocoa. The no-shade regime favoured the establishment of mistletoe, Tapinanthus bangwensis and mosses more than on the shaded plots. The intensity of the incident diffuse light and the humidity probably had a greater influence than the age of the tree on the development of mosses on the cocoa trunk and branches.