Characterisation of soil aggregate stability by ultrasonic dispersion

Abstract

Ultrasonic soil aggregate stability (USAS) of 5 European soils was investigated in ultrasonic dispersion tests, studying mass fractions of macroaggregates at different absorbed specific energy levels. The parameter %USAS (1.95 J ml -1 ) was calculated using the mass fraction of macroaggregates (2000-200 μm) at absorbed specific energy 1.95 J ml -1 , the respective mass fraction prior to sonification and the sand fraction greater then 200 μm after chemical dispersion. Soil aggregate stability (SAS) determined by the method of wet sieving (%SAS) served for comparison with the ultrasonic results. The same ranking of stability of the 5 soils was found using %SAS and %USAS( 1.95 J ml -1 ). %USAS(1.95 J ml -1 ) was found more sensitive than %SAS for dividing relatively stable soils and less sensitive for dividing relatively unstable soils. The vibration amplitude used in ultrasonic dispersion tests influences the dynamic of soil dispersion. At higher vibration amplitudes, the disaggregation of soil particles needs less absorbed specific energy.