DEVELOPMENT OF AN IMPROVED VERTISOL STABILITY TEST FOR SOILPAK

The stability in water of soil from 3 contrasting Vertisols was measur ed using 5 tests. Two end-over-end shaking procedures, the Loveday & P yle dispersion test, and the relatively rapid SOILpak procedure of Dan iells & Larsen were assessed. The latter method has been modified to d eal with several deficiencies such as its lack of score subdivisions; the new procedure is referred to as the 'aggregate stability in water' (ASWAT) test. We correlated data from all the tests under considerati on to provide definitions of the 'critical' point at which dispersion becomes a problem for land managers. Three soil management zones have been defined provisionally using data from the ASWAT and end-over-end 'aggregate stability' tests. The scheme allows appropriate surface soi l management strategies to be predicted using the ASWAT test. The rela tionship between data from the ASWAT test and exchangeable sodium perc entage indicated that factors other than exchangeable sodium strongly influence dispersibility of the samples under consideration.