MICROSCALIC VARIABILITY OF SOIL SOLUTION CHEMISTRY - RESULTS OF A LABORATORY EXPERIMENT COMPARING STANDARD SUCTION WITH MICROSUCTION CUPS

In a laboratory experiment with an undisturbed soil column, the chemis try of soil solution collected by a standard suction cup (empty set 2 cm) was compared with that of 20 micro suction cups (empty set 1 mm) i nstalled in the same soil depth. The standard cup showed comparable co ncentrations of inorganic anions with the soil column leachate, becaus e preferably the main water paths of the soil column were sampled. In contrast, about 30 % of the micro suction cups sample soil compartment s that have a different solution chemistry. In these cases the differe nces between standard and micro suction cups decrease in the order nit rate, chloride, sulfate. Standard suction cups seem to be the right sa mpling device for the investigation of element fluxes through soil. To get information about plant availability of ions they are inadequate, due to their dimension. Here micro suction cups are more appropriate, because their dimension is comparable to plant roots.