Thursday, November 16, 2006 - 9:15 AM

Acoustical Profile Identification of Soil Hydration and Stability.

Alvin Smucker1, Eun Jin Park2, Marisol Quintanilla1, Stuart Gage1, and George Bird1. (1) Michigan State University, 530 Plant & Soil Sci. Bldg., ., East Lansing, MI 48824-1325, (2) Gyeonggi Research Institute, Suwon, Korea, Kenya

New developments in the computer processing of environmental acoustics and ecosystem assessment were employed to identify soil porosity, compaction and tortuosity. Soil aggregates sampled from continuously tilled and non-tilled agricultural soils subjected to best management practices and nearby forest soils were evaluated for their acoustic frequencies generated by escaping air that was entrapped when soil aggregates were subjected to rapid hydration in sound-proof hearing analyses laboratories. Digital recordings of aggregate conditions during the rapid wetting were compared to the degree of slaking and complete disruption of weak aggregates. Acoustical frequency profiles were highly correlated to soil aggregate porosities and stabilities. Acoustical profiles of replicated solution treatments ranging from distilled water to highly dispersive sodium solutions were identified for different soil types subjected to various management treatments.  Acoustical signatures, eg., frequencies and decibels, across time, were determined for soil aggregates 6.3-9.5 mm across, with the goal of nondestructively quantifying numerous soil biophysical properties, including polar tensile strengths, intra-aggregate porosities, bulk densities and various water and mineral properties. Dimensionless thresholds separating the low from the high frequencies generated by a range of pores sizes filled during rapid wetting were determined by numerical analyses. These equations are used to compare acoustical frequencies with pore diameters within the aggregates. Acoustical signals associated with aggregate breakages will be used to identify soil aggregate turnover as additional acoustical signals are generated by larger volumes of soils containing natural and assembled volumes of multiple soil aggregate sizes. Conventionally tilled soils had less soil aggregate stability and greater sound intensity. Soils from natural ecosystems have higher soil aggregate stability and less sound intensity. These results suggest that soil acoustical profiles can be a useful and rapid approach for determining soil aggregate stability.