Physical and hydraulic characteristics in compacted clay soils

To determine and compare the differences in soil water suction between uncropped and cropped plots, a 52-plot experiment was used. Three average tyre to soil contact pressures of 31, 41 and 62 kPa as well as four numbers of machines passes (1, 5, 10 and 15) and control plots of zero traffic were used as pre-seeding machinery compaction treatments for the investigation. Soil dry bulk density, soil moisture content, soil suction, rainfall, water table depth and corn yield were all measured. The results showed that, with increasing tyre contact pressure, there was a corresponding increase in soil suction during the growing season in both uncropped and cropped plots. A family of curves was drawn for soil suction versus tyre contact pressure for different numbers of days and also for soil suction versus volumetric water content at varying contact pressures and times of the season. Growth performance of corn plants was best in moderately compacted plots. Dry bulk density and penetrometer resistance were related to traffic treatments.