COMPACTION AND SETTLING OF QUEBEC SOILS IN RELATION TO THEIR SOIL-WATER PROPERTIES

Twenty-one topsoils, with texture varying from sandy loam to clay and organic matter content ranging from 1.6 to 11.9%, were submitted to compaction and settling at different moisture contents where dry bulk density was determined. Under compaction, the density curve went through a maximum while a minimum was observed in the case of settling. Optimum moisture contents corresponding to these two characteristic densities were almost the same. The most important physical properties affecting soil behavior under compaction and settling were found to be water retention properties at low matric potential which themselves depended primarily on organic matter content. Samples submitted to compaction had saturated hydraulic conductivities less than 1 cm/h, while after settling, Ksat measurements ranged from 0.8 to 234 cm/h. Organic matter played an important role in reducing the effects of compaction, and moisture content alone was not sufficient to predict the best conditions for workability in the fields.