Relationships between shrinkage indices and soil properties in some New Zealand soils

Shrinkage is a physical process that has profound effects on the agricultural and engineering use of soil. This study was undertaken to assess the shrinkage potential of different New Zealand soils using the Coefficient of Linear Extensibility (COLE) and to examine relationships between soil shrinkage and selected chemical, physical and mineralogical soil properties. Results indicate that there is a wide range in the shrinkage capacities of different soils, with COLE values between 0.050 and 0.313. Allophane dominated soil samples showed the largest soil shrinkage, followed by montmorillonite and halloysite samples, with the least shrinkage occurring in the kaolinite/vermiculite and chlorite/illite dominated samples. There was a significant statistical relationship found between COLEstd determined using natural soil aggregates and COLErod determined using remoulded soil samples (R2=0.85, p<0.001). Both COLEstd and COLErod were found to be significantly related to specific surface area and soil clay content and inversely related to bulk density. COLErod was also significantly related to CEC. No relationships were found between shrinkage indices and organic matter. Multiple regression models with terms for specific surface area and clay content could explain 76% and 81% of the variance in shrinkage determined by COLErod and COLEstd, respectively.