Soil profile water content determination: Sensor accuracy, axial response, calibration, temperature dependence, and precision

Although the neutron moisture meter (NMM) has served the need for accurate soil water content determinations well, increasing reg-ulatory burdens, including the requirement that the NMM not be left unattended, limit the usefulness of the method. Newer methods, which respond to soil electromagnetic (EM) properties, typically allow data logging and unattended operation, but with uncertain precision, accuracy, and volume of sensitivity. In laboratory columns of three soils, we compared the Sentek EnviroSCAN and Diviner 2000 ca-pacitance devices, the Delta-T PR1/6 Profiler capacitance probe, the Trime T3 tube-probe, all EM methods, with the NMM and con-ventional time domain reflectometry (TDR, also an EM method). All but conventional TDR can be used in access tubes. Measurements were made before, during, and after wetting to saturation in triplicate repacked columns of three soils ranging in total clay content from 1