Micro-scale assessment of soil phosphorus in aggregates

Small-scale heterogeneity of element distributions recently has received increased attention in soil science due to its influence on soil functions and soil fertility. We investigated micro-scale P distribution and binding forms in siliceous soil aggregates by combining advanced spectrometric and spectroscopic techniques to introduce new insights on P accessibility and availability in soils.

Here we show that soil substrate and soil depth determine micro-scale P heterogeneity in soil aggregates. At the P-rich areas in all investigated soil aggregates, P was predominantly co-located with aluminium and iron oxides and hydroxides, which are known to strongly adsorb P. Clay minerals were co-located with P only to a lesser extent. In the low-P topsoil, more than half of the P was bound organically, probably as a result of retarded organic P mineralization.