The author tried to find out the reason of small tillage resistance of defomed rotary tillage machinery (like Spade Plow) by means of measuring resistance force, soil stress distribution in furrow slice and soil deformation.
At first, the energy required to accelerate a furrow slice was calculated through the motion study of blade. It was found that the accelaration energy might exceed 20% of total tillage energy in the conventional machine.
The cutting process is devided into two parts, namely, straight cutting and curved cutting. The cutting angle is so small that the resistance is quite low in the straight cutting process. The shearing action at the latter half of straight cutting process is bloked when the shear planes touch the bottom. Consequently, the resistance increases rapidly. In the process of curved cutting, shearing action without strong compression of furrow slice takes place. This contributes also to the small resistance of this tillage method.