Determination of Water in Surface Soils by Acoustic Methods.

摘要

The objective was to develop an acoustic method for soil moisture determination. Three phases of this research were: (1) Development of system to send and receive elastic waves through soils. (2) Development of an experiment to obtain accurate indications of acoustic transmission parameters. (3) Development of analysis and interpretive methods to obtain soil moisture information from acoustic measurements. The third phase,if successful,leads to a formulation of principles for the design of an acoustic soil moisture monitoring device. For a silt loam soil, a series of acoustic measurements from 0to 14KHz was taken for eleven moisture conditions from 0to 0.912of saturation. Simultaneously,gamma-ray density scanning of the sample provided independent measurement of the soil moisture profile. In the frequency range from 3600to 6975Hz these correlations indicated that acoustic transmission was an increasing function of soil moisture. Multiple regression analysis give two possible relationships. In the frequency range from 900to 1595Hz,the analysis yielded negative correlation indicating a tendency for acoustic loss to increase with soil moisture. Additional results in the frequency range 450to 675Hz gave positive correlations to soil moisture with different minimum regression lines. Further measurement and analyses would provide more extensive information applicable in formulating design principles for an acoustic soil moisture monitor and the development of a soil moisture instrument suited to a variety of soil types.