Impact of accumulation of copper from application of copper-based fungicides on soil properties in Ghana

Abstract

Black pod disease causes yield losses in cocoa production, and copper-based fungicides are used to control the disease. The study investigated the extent of accumulated copper from copper-based fungicides and interaction with soil chemical properties and microbial biomass in three communities: Akaasu, Kyeikrom, and Tuntum in the Bibiani–Anhwiaso–Bekwai District. Soil samples were collected at 0–15 cm and 15–30 cm. The fresh soil samples were divided into two, sieved and stored under different conditions; 4 °C and room temperature. Physicochemical (soil pH, Organic Carbon, Total Nitrogen) and microbial analyses (Microbial biomass was determined by the chloroform fumigation method and extraction and soil microbial mass of phosphorus) were conducted on the samples. Tuntum had the highest concentration of total copper (286.54 mg/kg), while the Akaasu cocoa plantation had the lowest total copper concentration (215.63 mg/kg). Extractable and total copper vary significantly (p < 0.05) in the three cocoa farms' (Akaasu, Kyeikrom and Tumtum) top and subsoils compared to the reference values. However, soil pH, nitrogen and organic matter from soils of the cocoa farms did not vary significantly (P > 0.05) from their reference soils. The correlation analysis revealed that extractable and total Cu at different soil depths (0–15 cm and 15–30 cm) correlated negatively with organic matter contents. There was negative correlation between extractable and total Cu with microbial biomass though not significantly different at p > 0.05 in all the study locations. Generally, the concentrations of copper in the soil at all sites have not reached their critical levels of 800 mg/kg.