A Three-stage Soil Layer Mixing Plough for the Improvement of Meadow Soil, Part 1: Mechanical Properties of Soils

Meadow soil in China consists of extremely fine soil particles, is quite impermeable and has particular mechanical properties. This paper deals with the mechanical properties of the three horizons (Ap, A and Cgl) of meadow soil as an aid to understanding the draught requirement of a three-stage soil layer mixing plough for the improvement of the meadow soil. Pseudogley soil which is a typical heavy clay soil in Japan was also tested for comparison. Tensile strength, shear strength, soil-metal friction and soil-plastic friction were determined. The results show that the tensile strength of the meadow soil increased steeply at lower soil water contents. In the range of soil water content of more than 30% d.b., the tensile strength of the A horizon is the largest, followed by the Cgl horizon, Ap horizon and pseudogley soil. The cohesive strengths of all soils showed a maximum at particular soil water contents. These soil water contents were nearly same as the plastic limits. Comparing the maximum value of the cohesion, the A horizon was the largest, followed by the Cgl, Ap horizon and the pseudogley soil. The adhesion to steel of all soils showed a maximum at particular soil water contents. These soil water contents were slightly larger than the plastic limits. Hence, the adhesion was highest under a wet soil condition. The maximum value for the adhesion of the A horizon was the largest, followed by the Ap, Cgl and the pseudogley soil. Hence, all horizons of the meadow soil were much stickier than the pseudogley soil. The adhesion to polyethylene was smaller than that to steel. The soil water content, at which the adhesion showed a maximum, was the same as that for steel.