Kinetics of phosphorus desorption from calcareous soils using DGT technique

Abstract The present study investigated kinetics of phosphorus (P) release from some calcareous soils employing DGT technique. For these purpose, DGT were deployed in ten calcareous soils for different time periods between 4 h and 21 days and the accumulated P were used to calculate the distribution coefficient for labile metal, K dl , desorption rate constants (k − 1 ) and the rate at which the soil system can resupply P from solid phase to solution (Tc) using the DIFS model. The values of K dl calculated from DIFS ranged from 0.67 to 198 cm 3 /g. Response times (Tc) were so short in six studied soils with low Olsen-P. A short response time means that the rapid resupply from the solid phase and slow depletion over time of the available P pool occurs. By contrast, the four rests of the soils have a longer response time (about 40 min) and so little the resupply from the solid phase, leading to a progressive depletion. The P desorption rate (k − 1 ) parameter derived from DIFS were from 9.9 ∗ 10 − 6 to 21.12 ∗ 10 − 4  s − 1 with a mean 4.54 ∗ 10 − 4 and well-correlated with the content and/or the concentration of P in corn shoot (r = 0.74, P