M. A. Malicki

A manually controlled TDR soil moisture meter operating with 300 ps rise-time needle pulse

SummaryThe principle of operation of a simple, manually controlled Time Domain Reflectometer (TDR meter) for soil moisture measurements, which operates with a needle pulse of 300 ps rise-time, is described. A block diagram and constructions are also given. Construction of a switchless multiple sensor probe, having an inherent delay reference, is presented. Results of measurements of the soil dielectric constant as related to water content, for soils having different bulk densities, textures and humus content show a high correlation. The results agree closely with other investigators measurements with different, more expensive, TDR instruments. The general principle of microprocessor-controlled TDR operated soil moisture meter is considered.

Application of time-domain reflectometry (TDR) soil moisture miniprobe for the determination of unsaturated soil water characteristics from undisturbed soil cores

SummaryConstruction and operating characteristics of a TDR soil moisture miniprobe, that can be inserted through the wall of a metal cylinder, are shown. A laboratory stand for monitoring unsaturated water flow in undisturbed soil cores, involving a set of TDR miniprobes in combination with a set of minitensiometers, is described. This stand was used for frequent readings of instantaneous profiles of moisture and matric potential during transition from saturated to air dry state, in order to compute the unsaturated soil water characteristics. Some methodical aspects of the applied data processing algorithm are outlined.

Investigations on power factor of the soil electrical impedance as related to moisture, salinity and bulk density

SummaryThe power factor of the soil electrical impedance was investigated for soils having different textures over a frequency range of 20 kHz–60 MHz. The measurements were carried out in laboratory conditions with different soil water and salinity levels. Within the frequency range of 1–3 MHz the power factor was not significantly affected by soil water contents higher than about 6% (volume) and was also not affected by soil salinity within a range of 0.3–20 dS/m. However, the soil bulk density did influence the magnitude of the power factor. Thus, measurement of soil bulk density, independent of soil water content and salinity, may be possible.