Non-destructive method for determining temporal and spatial changes of thesoil solution chemistry in the rhizosphere

A non-destructive method for sampling the rhizosphere soil solution at a hi gh spatial resolution is presented. A rhizobox, which enables to separate s oils in the rhizosphere, was combined with soil solution samplers with a lo oped hollow fiber (LHF-sampler). In a rhizobox, LHF-samplers were installed at a distance of 0-2 mm and 8-10 mm from the root surface. A pot experimen t was carried out for 17 d with two treatments, i.e. maize (Zea mays L.) an d no plants. During the experiment, soil solutions were collected on day 5, 9, 13, and 17, and analyzed for the ionic concentrations. After the experi ment, the soil samples mere also collected at a distance of every 2 mm from the root surface up to 10 mm and analyzed for soluble ion concentrations i n order to evaluate the degree of disturbance due to soil solution sampling . The method applied in this experiment enabled to sample the soil solution from the rhizosphere at a high spatial resolution with minimal disturbance . With plant growth, the concentrations of major ions except for SO42- in t he soil solution collected at a distance of 0-2 mm from the root surface be came significantly lower than those at 8-10 mm. This procedure led to the a lteration of the ionic composition, i.e. the predominance of SO42- instead of NO3-, only within a few millimeters from the root surface. These quantit ative results suggested that plant roots absorb the soil solution in the rh izosphere where the level of NO3- is relatively lower than that of the oute r solution and that other anions such as SO42- play an important role in re gulating the concentrations of cations and their supply to plants.