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 cel ls suitable for high resolution tensiometry and lysimetry have been de veloped, the construction of which is described in detail. The cells c onsist of a ceramic capillary with 1 mm diameter, connected to 1/16'' ( 1.59 mm) PEEK tubing. When combined with a pressure transducer the m icro ceramic cells act as tensiometer, when coupled to a vacuum collec ting device they can be used as micro suction cups. Also a combined te nsio-lysimeter was constructed, but this application is limited to low er soil matrix potentials. The micro suction cups showed a quick respo nse to changes in the outer solution (breakthrough volume <80 mu l). I n 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.