DEVELOPMENT OF CONE PENETROMETER FOR INVESTIGATION OF SOIL COMPACTIONCAUSED BY AGRICULTURAL VEHICLES IN MEADOWS

The authors developed an instrument that enables to measure the penetr ation resistance easily and accurately to evaluate the extent of soil compaction generated by the traffic of vehicles in the meadows. The in strument is composed of a cone as a penetrating part, a part for measu ring the penetration resistance, a part for measuring the penetration depth, a part for recording data, a part for horizontal positioning, a nd a hanging part. It was possible for the cone to penetrate into the soil with a constant speed through the motor of the penetrating part, and to penetrate vertically even in the case of sloping land by using the part for horizontal positioning. A carrier was used to move among the measured points in the field. Measurement area was limited to the area where vehicles moved, namely the inclination of the area for meas urement was less than about 25 degrees. The average time required for one measurement was about 2.3 min. It was confirmed that the use of th is instrument enabled to measure the penetration resistance easily and frequently and to generate a distribution map of the penetration resi stance to determine the position or spread of the hard pan.