Effect of Cocoa Pod Husk Compost Produced Using Rot Fungi on the Growth of Cocoa Seedlings

Abstract

Rot fungi have the ability to decompose organic materials into simple compounds or elements as nutrients for plants. In the process, rot fungi produce secondary metabolites and absorb phosphate from their substrates so that the phosphate become available to plants. The purpose of this study was to identify the species of rot fungi isolated from decaying cocoa stems and to determine the ability of the rot fungi insolubilizing phosphate and the effect of the husk compost on the growth of cocoa seedlings. The rot fungi were isolated and purified before they were grown on solid Pikovskaya’s media amended with 0.5% tricalcium phosphate (Ca₃PO₄) as a phosphate source. In addition, the effects of compost addition to growth medium (soil: compost = 2:1) on cocoa seedling growth was also determined. The results showed that there were eight species of rot fungi isolated from dead cocoa trees: Mycena sp., Lycoperdon sp., Auricularia sp., Schizoshyllum sp., Coprinus sp., Tremetes sp., Pleurotus sp. and Tremella sp. All isolates were capable of solubilizing phosphate from substrates but amongst all isolates, Lycoperdon sp. and Pleurotus sp. were the most effective in solubilizing phosphate, 3,198 and 3,094 μg L^-1, respectively. Effect of the compost produced using these two rot fungi on plant growth variables: the ratio of leaf area, plant dry weight, root canopy ratio and net assimilation rate, were comparable to chemical fertilizers. Thus, Lycoperdon sp. and Pleurotus sp. are promising decomposing agents for producing high quality compost made from cocoa pod husks as an alternative to inorganic fertilizers.