Field calibration of a neutron moisture meter in a cracking grey clay

Summary A neutron moisture meter was field calibrated in a cracking grey clay prepared for furrow irrigation at Narrabri, N.S.W. Neutron counts were taken in successive 0.1 m increments between the 0 and 1.5 m depths. Concomitant measurements using undisturbed soil cores provided independent estimates of volumetric water content. Separate linear calibrations were required for the 0–0.1 m, 0.1–0.2 m and 0.2–1.5 m depth increments. Correction for bias due to cracking and changes in bulk density slightly improved the calibrations. The accuracy of predicted soil water content was improved relative to previous calibrations. A precision of ±0.01 m³m^–3 required 3 samples per mean by the neutron method or 11 samples per mean by the core sampling method.