ANALYZING THE PERFORMANCE OF A MICRO SOIL SOLUTION SAMPLING DEVICE INA LABORATORY EXAMINATION AND A FIELD EXPERIMENT

The performance of a micro soil solution sampling device was tested in a laboratory examination and in a field experiment. The instrument al lows detection of temporal and spatial changes in soil solution chemis try at a spatially high resolution. The flexible tube of the suction c ell is made of a porous polymer with a diameter of 2.3 mm. To achieve more stability and to minimize disturbance of the instrument during fi eld installation, the original device was modified by embedding the su ction cell in a stainless steel and pressure absorbing corpus. During a laboratory test the new sampling system was compared to ceramic P-80 suction cells. Solution samples taken with the new device adapted mor e quickly to the given concentrations compared to the ceramic suction cells. In a field test, micro samplers were implanted in an existing s oil solution monitoring plot, equipped with standard ceramic samplers. Bi-weekly sampling using the micro cells indicated high temporal and spatial variation, and in June 1995 it was possible, to identify a dis tinct nitrification. However, in a statistical comparison of the entir e sampling period and respective sub-sampling areas the two sampler ty pes indicated identical concentration ranges for nitrate. It is conclu ded that the new micro samplers can help to identify processes in soil s which may cause short-term changes in the soil solution chemistry, w hereas the standard sampling technique with ceramic cells seems to be still a suitable tool if long-term mean soil solution concentrations a re to be measured.