Compression of Agricultural Soils from Eight Soil Orders

Abstract Compression curves (bulk density vs. log applied stress) determined on 36 world agricultural soil samples at a given water content were linear over the range of stresses from about 1 to 10 kg cm −2 . Compression curves determined for soils at different water contents were approximately parallel to each other over the range of initial pore water potentials from −0.05 to −1.0 bar. The compression index, C (slope of the compression curve), increased approximately linearly as clay content of the soil increased up to about 33% and then remained approximately constant as clay content further increased. The maximum C value was 0.55 for soils with predominantly 2:1 type clays and 0.50 for soils with predominantly kaolinite or iron oxides in the clay fraction. If the compression curve at one water content is known, a procedure is suggested to predict compression curves at other water contents.