Abstract :
A model spot plough to invert the soil slice within its own furrow was designed and tested in a soil bin, with a view to overcoming the disadvantages of conventional tillage systems with mouldboard ploughs. The model was especially designed to avoid soil clogging, whilst the basic structure was not altered from that surveyed from previous research. Followed by the share and main mouldboard at the beginning of the inversion, a tilted disc coulter (TDC) was located on the other side of the main mouldboard to assist the spot inversion and to reduce relative motion to the soil. Towards the end, the tilted disc coulter was replaced by a sub-mouldboard. Optimum width-todepth ratio and width of the mouldboards were also considered. The mouldboards were expressed as helicoidal surfaces, and were fabricated from a plate of polyvinyl chloride. A series of experiments showed that the model spot plough performed well in wet-plastic soil, acceptably in dry-powdery soil at higher speed, and somewhat less steadily in dry-solid soil conditions. In any soil condition, the function of the rotating tilted disc coulter was found to be essential for stable operation.
