Simultaneous Quantification of Soil Phosphorus Labile Pool and Desorption Kinetics Using DGTs and 3D-DIFS

Area of Science:

• Soil Science
• Environmental Chemistry
• Plant Nutrition

Background:

• Soil phosphorus (P) buffering by the solid phase is crucial for plant nutrient access.
• The labile solid-phase P pool and its resupply rate dictate nutrient availability.
• Understanding P dynamics is key to managing soil fertility and crop yields.

Purpose of the Study:

• To evaluate the labile phosphorus pool (P_labile) and desorption kinetics in UK agricultural soils.
• To compare DGT-derived P_labile with conventional soil P extraction methods.
• To assess the performance of different DGT-induced fluxes in the soil and sediments (DIFS) model versions.

Main Methods:

• Utilized the diffusive gradients in thin-films (DGT) technique to measure P_labile and desorption kinetics.
• Applied the DGT-induced fluxes in the soil and sediments (DIFS) model to time-series DGT data (1-240 h).
• Compared DGT-derived P_labile with Olsen P, FeO-P, and water-extractable P.

Main Results:

• Olsen P overestimated desorbable P by six-fold compared to DGT.
• DGT and DIFS modeling provided estimates of P_labile and system response time (T_c).
• Different DIFS model dimensions (1D, 2D, 3D) showed good fits but poor parameter agreement; 3D was most precise.

Conclusions:

• DGT is a more accurate method for assessing labile soil phosphorus than conventional extracts like Olsen P.
• The DIFS model requires careful consideration of assumptions and dimensionality for reliable kinetic parameterization.
• Accurate labile P quantification is essential for understanding nutrient limitations in agricultural soils.