Interactions of the cutting edge of tillage implements with soil

The effect was studied of the cutting edge geometry of tillage implements on tillage forces, soil failure and soil movement below the tillage depth. Tests were conducted using 400mm wide experimental sweeps under the controlled conditions of a tillage test track (large outside continuous soil bin) and in the field. Corresponding tests were also conducted using a glass-sided soil bin to help quantify the interactions between the soil and tillage implements. By changing from a tillage tool with a sharp cutting edge geometry to a blunt one, the results showed that the draught force of a tillage tool with a similar overall geometry could be increased by up to 80% and the direction of the vertical force could be altered from one which acted to pull the tool into the soil to a force which provided tool lift. X-ray transmission, soil pore counts and cone penetrometer measurements, during the experimental sweep tests showed that the blunter cutting edges often formed cracks in the soil below the tillage depth. During the tillage test track tests a small angle of interference (negative clearance between the underside of the tool and the soil) increased the cone penetration resistance of the soil below the depth of tillage. Corresponding tests in the glass-sided soil bin revealed that the tool smeared the soil as the cutting edge passed. (C) 1996 Silsoe Research Institute.