Physicochemical and biological properties of different Cocoa Pod Husk-based composts

Abstract

The objective was to evaluate the properties of cocoa pod husk-based composts for potential application as soil amendments for crop production. The physicochemical and biological properties of the compost types were analysed. Four compost types were prepared by mixing cocoa pod husk, poultry manure and Panicum maximum in different proportions. A phytotoxicity test was carried out using maize (Zea mays L.) to test whether the compost types contain substances that inhibit seed germination or growth of the radicle. Bulk densities of the compost types were higher than 0.160 Mg m^-3, an indication that the compost types as soil amendment will restrict root growth thereby inhibiting plant growth. The average pH of the compost types falls within the optimum range of 6.5 to 8.5 and thus, the composts are stabilized. The compost types had high nitrogen content, so when utilized as a soil amendment would improve the nitrogen content of soils. Copper concentrations in the compost types were far below the WHO/FAO permissible limit of 100 mg kg^-1, therefore can be applied at high rates without any problem of copper accumulation in soil. Phytophthora palmivora and Phytophthora megakarya were not detected from the compost types, therefore the compost types could be used without Phytophthora disease infection. Germination percentage and germination index showed that the analyzed compost types achieved high percentages of the germinating capacity of maize seeds and had no phytotoxic substances. The cocoa pod husk-based composts showed substantially varied physicochemical and biological properties suitable to support plant growth. The results clearly showed that, CPHcomp3 made from CPH residues, poultry manure and Panicum maximum at the ratio 6: 1: 2 mixture is recommended for use as a soil amendment for crop production.