Effect of organic substances on iron-release kinetics in a calcareous soil after basil harvesting

Desorption of iron from soil is important for evaluating the availability and toxicity of soil Fe in agriculture. The aim of this investigation was to study the effect of organic substances (cow and sheep manures and vermicompost) on Fe release from a calcareous soil and determine the best models for the description of the Fe desorption kinetics. Organic substances were added to soils at the rate of 3 %. Basil (Ocimum basilicum L.) seeds were sown in each pot and pots were kept at 24–25°C at about field capacity for 90 days. After 90 days, plants were harvested and soil samples were used for Fe desorption analysis. Seven kinetic models were evaluated to describe the rate of Fe desorption in soil extracted with diethylenetriaminepentaacetic acid (DTPA). Results showed that Fe release from soil samples increased with time. Release of Fe was rapid at first and then became slower. Iron release in the organic substances treatments was higher than in the unamended soil and the two-constant rate, parabolic diffusion and simple Elovich models were the best equations for the description of Fe release from soils