Application of Cu fertilizer on Cu recovery and desorption kinetics in two calcareous soils

Desorption of copper (Cu) is an important factor in determining Cu availability in calcareous soils. The aims of this investigation was to study the influences of application of Cu fertilizer on copper desorption and recovery of two calcareous soils of Iran and determine the best models for description of the kinetics of Cu release in these soils. For this purpose, copper sulfate (CuSO₄·5H₂O) fertilizer at the levels of 0, 3, 5 and 10 mg of Cu per kg of soil was mixed with soils. The soils were incubated at 25 ± 1 °C and near field capacity for 90 days in the greenhouse. For Cu desorption studies, samples were extracted with 0.01 M EDTA at pH 7.0 with shaker for periods of 5–2,880 min. Results showed that in each of the two soils, the amount of cumulative recovery and desorption of Cu from fertilized samples increased with the increase in the level of Cu fertilizer. Two-constant-rates and simple Elovich were the best equations for description of Cu desorption from soils. Release rate constants of these equations in the fertilized soils were greater than in unfertilized soils.