Draft-speed relationship of simple tillage tools at high operating speeds

Field experiments were conducted with five different blades operated vertically in sandy loam and clay soil types up to a speed of 18 m s(-1) to determine the draft-speed relationships at high speeds, The soils were Calcic Chemozem and Haplic Kastanozem according to FAO classification. Mechanical properties of the soils were determined to correlate the results with model predictions, The results showed that the draft increased less above a critical speed range of 3 to 5 m s(-1). This critical speed range was compared with: the propagation speed of a longitudinal pressure wave in the soil, the speed of the soil particles caused by this pressure wave in the soil, and the speed of disruption of the soil. It was shown that these speeds are related to the observed critical speed range. As previously proposed, the amount of soil deformation due to tillage would decrease above the critical speed range, It is, therefore, important to examine the dynamic effect of tillage at higher operating speeds.