Soil water content

Soil water content is measured with a Time Domain Reflectometer (TDR, Campbell Scientific TDR-100) connected to datalogger (Campbell 21X), nine multiplexers (SDMX50) and 64 probes. The probes are of two rod types, 15 cm long and installed vertically in the upper horizons and slightly descending deeper in soil. There are sensors in each pit and in the mineral soil walls of the weir. The two rod type probe was selected in order to enable installation into the stony soil. The datalogger controls the measurement sequence, applies algorithms (Ledieu 1986) for transforming the apparent sensor length to the soil water content and serves as the first storage site for the calculated results. The memory of the datalogger is read automatically daily to the main computer through a modified RS232/485 line. Also the electrical conductivity of the soil solution is measured with TDR.