Clay mineralogy as affecting disaggregation in some palygorskite containing soils of the Jordan and Bet-She'an Valleys

The influence of clay mineralogy on disaggregation in some palygorskite-con taining soils of the Jordan and Bet-She'an Valleys was examined. The disagg regation potential of different minerals in the soil clay fraction was inve stigated by establishing differences in the mineral suite between the origi nal and disaggregated clay fractions. By shaking the soil with distilled wa ter, calcite, dolomite, feldspar, and palygorskite were disaggregated prefe rentially. The pattern for quartz was inconsistent. Among phyllosilicates, palygorskite was the most strongly, disaggregated, while smectite was the l east disaggregated mineral. The disaggregation potential of kaolinite was o f intermediate value. By shaking the soil with 0.01 N NaCl, calcite and dol omite were released preferentially, and were the dominant minerals in the d isaggregated clay fraction. Scanning electron microscopy observations indic ate that palygorskite fibres do not associate into aggregates in soils and suspensions, even when saturated with calcium ions. The present findings ar e relevant for soils with low exchangeable sodium percentage. These soils c an be expected under rain-fed agriculture or irrigation with high quality w ater which has a low sodium adsorption ratio.