Soil solution chemistry in the rhizosphere of roots of sessile oak (Quercus petraea) as influenced by lime

This study describes the soil solution chemistry in the rhizosphere of fine roots of sessile oak ( Quercus petraea (M.) Liebl.) grown in rhizotrons. A control was compared with soils treated with an equivalent CaCO3 of 1.4 t ha(-1) CaO. Solution samples were extracted from the B-horizon using micro suction cups with a suction of similar to 40 kPa. Two series of experiments were carried out: one irrigated with rain water (age of seedling 2 to 4 months) and one irrigated with demineralized water (age of seedlings 1.5 to 2 months). Half of the sampling points were choosen close to the roots and half in the bulk soil. In both experiments there was generally no rhizospheric gradient after liming. In contrast, in the control, depletion in the rhizosphere occurred for most of the ions studied (Mg, Ca, Al, K, NO3-, NH4+, Cl-) in the demineralized water experiment, but this was different when rainwater was used. The latter effect is probably due to the higher solution concentrations in the rainwater experiment but could also be a result of root damage due to low Ca/Al ratios in the rhizosphere solution. It was concluded, that liming improved the chemical composition in the rhizosphere soil solution by increasing overall solute concentration to levels enabling sufficient and easier nutrient uptake by roots.