Soil Chemical Properties in the Vicinity of Pores with and without Roots

Rhizosphere conditions are of great importance for nutrient uptake and thus plant growth. Nutrient availability in the rhizosphere may differ substantially from that of the bulk soil and specific sampling of the rhizosphere soil is crucial to the understanding of plant growth, particularly where roots are restricted in growth due to high bulk density of the soil. The purpose of this study was to develop suitable methods for investigating the chemical composition of soil around pores with and without roots in soils with high bulk density. Two different methods were undertaken: one approach was to perform sequential extractions with H2O, 0.01, 0.1, and 1 M NH4NO3 on soil samples taken at different distances from the pore wall to determine differences in element availability. Another approach was to analyze resin‐impregnated, undisturbed soil samples from the same site for elemental composition of pore wall material using a scanning electron microscope (SEM) equipped with an x‐ray micro analyzer. In general, the sequential extraction detected few statistically significant differences in nutrient availability between pores containing roots compared with pores without roots. The SEM analysis showed lower amounts of easily weatherable minerals around pores containing roots. Both methods are suitable for investigating differences between rhizosphere and bulk soil characteristics.