Effects of Parent Material and Land Use on the Variability of Available Cu in a Wetland Soil under Long-Term Farming System

The study was carried out in the dry season to evaluate the variation in available Cu in wetland soil under long-term farming systems. Twenty four surface (0-20 cm) composite soil samples of acidic nature were obtained and analyzed for available Cu in the soils using five extractants (0.01M HCl, Coca-cola, 0.05M EDTA, 0.05M DTPA, and 1N NH4OAc) respectively. Some important soil char- acteristics like soil texture, pH, SOM, and ECEC were also determined and corre- lated with the extractable Cu. The result shows that the content of available Cu varied significantly from 1.72-10.76 mg kg-1 by DTPA and Coca-cola methods, and these were rated from low to moderate, respectively. The study further shows that, the comparative extraction capacity of these extractants followed the order: Coca-Cola > O.1N HCl > 0.05M EDTA > NH4OAc > 0.005M DTPA. The wide variability of the available Cu in the wetland soils under long-term farming sug- gests that the availability of Cu in the soil are haply influenced by the agricultural locations, type of land use systems and soil parent materials, respectively. Corre- lation data also indicated that the fractions of Cu by different extractants were in a state of dynamic equilibrium and dependent were on pH, organic matter, ECEC, and clay content. The marginally Cu content of the wetland soils suggests that the use of integrated organo-mineral fertilizer with copper sulphate com- pound (CuSO4.5H2O) is required to boost the soil Cu and hence increased crop production.