The Measurement Of Soil Moisture And Density By Neutron And Gamma Ray Scattering

Evaluates methods for measuring soil moisture and describes the equipment used.

Provides information on where to go to find detailed guidance on how to use these techniques. Covers: remote sensing & surface geophysical methods; drilling & solids sampling methods; geophysical logging of boreholes; aquifer test methods; ground water sampling methods; Vadose Zone (VZ) hydrologic properties: water state, infiltration, conductivity, & flux; VZ water budget characterization methods; VZ soil-solute/gas sampling & monitoring methods; & chemical field screening & analytical methods. Charts, tables, graphs & drawings.

Sources of error that have been identified on the gamma-ray soil density gauge are: (1) sensitivity to local density variations, especially at the soil surface, (2) sensitivity to soil composition, and (3) inaccurate calibration techniques. An attempt was made to solve these problems by developing for each gauge calibration models that enable stable and homogenous non-soil standards to be used for calibration. Calibration standards and calibration models for each gauge were found and tested. In the process of developing and testing the new nuclear gauge calibration model, the dual-gauge principal of compensating these gauges for variations in soil composition was discovered. The air-gap method of using this principal is explained and was optimized by using the calibration model developed in the current study.