THE CHARACTERIZATION OF SOME SCOTTISH ARABLE TOPSOILS BY AGRICULTURAL AND ENGINEERING METHODS

Samples from fifty-eight arable topsoils in south-eastern Scotland were analyzed for compactability, plasticity, organic matter content, particle density, and particle-size distribution. The samples were classified by the methods employed for engineering soils and the groupings so obtained were compared with the textural classes. The criteria for the classification of engineering soils provide useful information on the likely mechanical behaviour of arable soils in the field. Tests were made for correlation between fifteen soil properties. The organic matter content, which in the samples studied ranged from 2 to 10 per cent, was shown to influence several mechanical properties, including optimum moisture content, maximum dry bulk density, liquid limit, and plastic limit. Maximum bulk density and optimum moisture content were strongly correlated with Atterberg limits and organic matter content. The liquid limit was more closely correlated with particle-size distribution than was the plastic limit. Unlike soils encountered in engineering, the particle density of these soils was not correlated with particle-size distribution but, like the Atterberg limits, was strongly correlated with organic matter content.