Changes in soil aggregate stability during simulated weather cycles

摘要

The effects of wetting and drying, and freezing and thawing on the stability of aggregates produced by laboratory manipulation or field tillage were studied on two British soils. Changes in aggregate stability were assessed by turbidimetry, with some information from microstructural changes at the surface of the aggregates using the scanning electron microscope (SEM). After 3 to 6 cycles of wetting and drying, and freezing and thawing the stability of sterilized and unsterilized remoulded aggregates recovered to that of natural aggregates. This recovery is explained in terms of thixotropy. Repeated weather cycles decreased the stability of field aggregates. The reduction in stability was greater for sterilized than unsterilized aggregates, suggesting that in the former, bond reformation due to biological activity counteracted the physical destruction caused by wetting and drying, and freezing and thawing.