DETERMINATION OF THE CONTENTS OF CLAY‐SIZED PARTICLES IN SOILS

Abstract

Summary: Edwards and Bremner's (1967) technique of dispersing soils by Bonification to form stable suspensions for particle‐size analysis without the addition of dispersant has been tested on a range of soils and a chalk. Carbonate soils or acid soils, containing a suite of minerals which normally form flocculated suspensions in water, yielded stable suspensions in water if the soil organic matter content was sufficiently high. With similar soils, low in organic matter, dispersant had to be added to stop partial flocculation of the test suspensions. Any gypsum present in soils has to be removed to prevent flocculation. For soils very strongly aggregated by organic matter, all the < 2 μm particles present can be released only by sonic vibration in dispersant rather than water.On four soils studied in detail, the maximum amounts of < 2 μm particles obtained by sonic vibration, vigorous shaking, and the I.S.S.S. method have been compared. On three of the four soils, the values were in close agreement.