Kinetics of phosphorus desorption from calcareous soils using DGT technique

- The DGT technique is suitable tools for studying P desorption kinetics.
- We obtained correlation between clay concentration with P desorption rate by DGT.
- We obtained the DGT technique sensitive to soil properties.
- The kinetic parameters by DGT have been shown to correlate with P uptake in corn.

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, Kdl, 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 Kdl calculated from DIFS ranged from 0.67 to 198 cm3/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 < 0.05) and root (r = 0.71, P < 0.05) confirming the importance of P desorption rate in plant P nutrition in the calcareous soils. In these study, the close correlation was obtained between clay and calcium carbonate equivalent concentration with P desorption rate that demonstrate DGT technique sensitive to soil properties and may allow the study of root-induced changes in rhizosphere.