Electromagnetic determination of water content: Measurements in multi-wire probes with electrical impedance discontinuities

The knowledge of soil water content is important for agriculture, mainly the determination of its variation in the soil profile in order to optimize irrigation management. The tendency to use the technique of TDR (rime Domain Reflectometry) to measure the soil water content is relatively new in Brazil. To help the diffusion of the technique, the objective of this work is to study the possibility of using the multi-wire probes with electrical impedance discontinuities in TDR equipment. The experiment was divided in to two parts. In the first one, the laboratory performance of two multi-wire probe configurations was studied; and in the second part, the probes reliability to monitor the water content variation in a porous media profile was evaluated. The viability of the use of multi-wire probes to estimate the water content in the porous media profile was confirmed. However, the use of probe with 0.10 m segmentation should be limited to a soil depth of 0.40 m, due to the difficulty to interpret the impedance peaks in its extremities.