Characterization of Copper Fractions in Soil of A Cocoa Plantation Treated With Bordeaux Mixture At Ajata Bende In The Rainforest Agro - Ecological Zone Of Nigeria

Abstract

Soil characterization of various copper fractions in a cocoa (Threobroma cacao) plantation treated with Bordeaux mixture, on a clayey soil at Ajata in Bende, Abia State, Southeast agro – ecological zone of Nigeria, was conducted. The sequential extraction process was used to separate copper into its operationally defined fractions namely: water soluble, exchangeable, organic matter, manganese oxide, amorphous iron oxide, and crystalline iron oxide, residual, available and total forms. Result showed that copper forms in the soil were affected by the application of Bordeaux mixture, in the dry and wet seasons. The exchangeable and Mn oxide fractions had the least (0.22 mg kg^-1) and highest (14.40 mg kg^-1) Cu levels, respectively in the wet season and 0.23 and 25.10 mg kg^-1 respectively in the dry season. Seasonal variation had no effect on water soluble, exchangeable and residual Cu forms. It greatly influenced the organic matter, Mn oxide, amorphous Fe oxide and crystalline Fe oxide forms. Manganese oxide and amorphous iron oxide forms of Cu were higher in the dry than the wet season and they served as sink for Cu. There was strong correlation among such soil properties such as CEC, silt and clay, and the various Cu forms. The results showed that application of Bordeaux mixture in the cocoa plantation increased the copper content in the soil above the critical value (0.20 mg kg^-1) for optimum growth and of cocoa.