AN EXAMINATION OF THE END-OVER-END SHAKING TECHNIQUE FOR MEASURING SOIL DISPERSION

The end-over-end shaking technique has been widely used to provide a m easure of soil dispersibility. However, results are dependent on the s pecific methodology employed. This paper investigates the effect of va rious physical parameters on the dispersion produced using an end-over -end shaking technique. Significant (P < 0.05) increases in the percen tages of clay (D-2) and silt+clay (D-20) particles dispersed as a prop ortion of the total soil weight were observed with increasing period o f shaking, suspension concentration, container size, and air-gap above the suspension. However, differences due to suspension temperature an d soil texture were either relatively minor or insignificant (P > 0.05 ). To enable better comparison of results from different workers, the following methodology for end-over-end shaking studies is proposed as a standard. The soil sample should be air-dried and crushed to pass th rough a 2-mm sieve. The air-dried equivalent of 50 g oven-dried soil s hould then be immersed in 1 L double-deionised water at 20 degrees C w ithin a 1.425-L cylinder (70 mm internal diameter) and shaken end-over -end at 20 rpm for 30 min before measuring the amount of dispersed <2 and <20 mu m material produced. The amount of dispersed material shoul d be expressed as a proportion of the total soil material.