Does magnetite have an influence on measurements of water contents by timedomain reflectometry (TDR)?

An experiment was carried out to investigate an assumed influence of magnet ite on TDR pulses. Sand was enriched with three different magnetite concent rations and six different volumetric water contents. The results of this sa nd standard experiment showed that magnetite up to a concentration of 6% (w /w) has no distinct influence on TDR measurements. Significantly higher wat er contents measured by TDR in the treatment with 6% magnetite compared to those with 0, 0.5 and 2% magnetite can be explained by the effect of the he avy clay-size magnetite (<2 mu m, rho = 5.1 g cm(-3)) on soil texture and b ulk density. This was confirmed by a comparative investigation of three san dy topsoils. Measurements with vertical vs horizonal TDR-probe position gav e the same results.