Accumulation of Copper from Application of Copper-Based Fungicides and its Relationship with Soil Chemical Properties and Microbial Biomass in Bibiani-Anhwiaso-Bekwai District of Ghana

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Black pod disease is a major cause of yield loss in cocoa production worldwide and the disease is mostly controlled by copper-based fungicides. However, prolong usage of these fungicides might have negative impact on soil fauna and other soil chemical properties. Ghana Cocoa Board continues to assist farmers to spray their cocoa farms with copper-based fungicides. This study was conducted in selected cocoa farms and uncultivated forests close to these farms which have never been sprayed with fungicides as reference. The study was to investigate the extent of accumulation of copper from the application of copper-based fungicides and its relationship with soil chemical properties and microbial biomass in three communities namely Akaasu, Kyeikrom and Tuntum in Bibiani-Anhwiaso-Bekwai District. Soil samples were collected at two distinct depths, 0-15 cm and 15-30 cm. The fresh soil samples were divided into two. One was immediately sieved through 4 mm mesh and stored at 4 0C for the soil microbial test. The other half was air dried, sieved through a 2 mm mesh and stored in plastic bags for the chemical analysis. Results showed that Tuntum cocoa plantation recorded the highest concentration of total copper (286.54 mgkg-1) while Akaasu cocoa plantation recorded the least total copper concentration of (215.63 mgkg-1). Extractable and total copper vary significantly (P < 0.05) in both top and sub soils of the cocoa plantations from their respective reference values. However, soil pH, nitrogen and organic matter from soils of the cocoa plantations did not vary significantly (P > 0.05) from their reference soils. Results from correlation analysis revealed that extractable and total copper in both the top and sub soils correlated negatively with the levels of organic matter. The relationship between extractable and total copper with microbial biomass were also negatively correlated but not significant (P > 0.05) from the regression analysis in all the study locations. The findings have also shown that the concentrations of copper in the soils of cocoa plantations have not reached their critical levels.
A thesis submitted to the Department of Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirements of Master of Science degree in Environmental Science, 2016