Improvement of planosol solum .2. Optimization of design of roll-in ploughs in soil bin experiments

Soil bin tests were conducted in Japan to optimize the shape of a roll-in plough which was an improved form of the stand-up plough reported in Part 1 of this paper, for soil mixing of the second (Aw) and third (B) horizons to improve the planosol solum in China, leaving the first (Ap) horizon undisturbed. The stand-up type plough consisted of three plough bodies and had the least draught and gave good soil mixing in the work reported in the Part 1 paper. In order to improve the stand-up plough, the optimum radius of curvature of the mouldboard, the plough height and the working depth to achieve greater soil mixing, were determined with half-size model ploughs. The results showed that with the roll-in type of plough, there was a relation between the radius of curvature of the mouldboard, the plough height and the working depth to cause soil mixing by rolling in. Using half-size model ploughs, with a working depth of 200 mm (Aw horizon 100 mm + B horizon 100 mm), the best soil mixing was obtained when the height of the first plough body was 210 mm, the radius of curvature was 140 mm, the height of the second plough body was 250 mm and the radius of curvature was 167 mm. (C) 1996 Silsoe Research Institute