A SENSITIVE PENETROMETER FOR MEASURING SOIL PENETRATION RESISTANCE

Soil compaction is one of the main negative factors that limit plant growth and crop yield. Soil mechanical resistance can be used as an indicator of soil compaction. This study is focused on the design of a penetrometer, which can make instantaneous soil resistance measurements in the soil without human faults. The penetrometer consists of a load cell, an electric motor, an internal helical screw rod, a probe, bubble balances, a graduated scale, a digital screen, a battery and additional attachments. Laboratory calibration and tests were carried out. In the field, according to a soil depth of 0-15, 15-30, 30-45 and 45-60 cm soil penetration resistance was measured in the field under different conditions of soil moisture content and soil bulk density. General results showed that, in un-compacted soil, range of soil penetration resistance values were 0.306 and 0.991 MPa whereas, in compacted soil, the range of penetration resistance were 0.891 and 2.371 MPa, respectively at 30-45 cm soil depth under different conditions of moisture content and bulk density. In conclusion, the experimental results showed that the designed system works quite well in the field and the vertical static penetrometer is a practical instrument for providing direct soil penetration resistance measurements.