A system for microscale tensiometry and lysimetry

Growing roots, soil structure and soil horizons may induce microscale heterogeneities of soil solution chemistry and soil water content. To investigate heterogeneities on the centimeter scale, micro ceramic cells suitable for high resolution tensiometry and lysimetry have been developed, the construction of which is described in detail. The cells consist of a ceramic capillary with 1 mm diameter, connected to 1/16'' ( 1.59 mm) PEEK tubing. When combined with a pressure transducer the micro ceramic cells act as tensiometer, when coupled to a vacuum collecting device they can be used as micro suction cups. Also a combined tensio-lysimeter was constructed, but this application is limited to lower soil matrix potentials. The micro suction cups showed a quick response to changes in the outer solution (breakthrough volume <80 mu l). In initial field studies, the pH of the soil solution of an acid forest soil was measured in high spatial resolution using a matrix of micro-lysimeters.