A method for characterizing the state of compactness of the plough layer

Abstract

A method for characterizing the state of compactness of the plough layer is described. The “degree of compactnes” is defined as the ratio (%) of the dry bulk density of the soil and the dry bulk density of the same soil in a compacted reference state. The bulk density in the field is determined by a frame-sampling technique. The reference state is determined by a drained, uniaxial compression test using wet soil samples which are loosely filled in an oedometer and loaded with a pressure of 200 kPa until drainage ceases. In a series of 100 field experiments with spring barley this method was method was used for characterizing the state of compactness of the annually tilled soil layer. On mineral soils, maximum crop yield was obtained at the same degree of compactness irrespective of soil type, which was the main goal of the method. For organic soils a modification of the procedure for determining the reference bulk density is required.