Effects of direction of rotation of a rotary tiller on properties of Bangkok clay soil

Experiments were conducted in a Bangkok clay soil to investigate the effects of reverse rotation of a rotary tiller on soil properties. Tests were conducted in wet land as well as in dry land. The performance was compared with that of the conventional C-type rotary tiller under similar conditions. New types of blades were designed for mounting on the reverse-rotary tiller. Tests were conducted at tractor forward speeds of 1.0, 1.5 and 2.0 km/h. The results indicated that the reverse-rotary tiller performed better than the C-type rotary tiller in terms of chopping and burial of weeds. The C-type rotary tiller performed slightly better than the reverse-rotary tiller in terms of puddling index (maximum 33% compared to 26.3% by rotary tiller), viscosity, falling cone penetration (minimum cone index of 116.7 kPa compared to 180.1 kPa for rotary tiller) and bulk density reduction. Shear strength and cone index values (% reduction in cone index ranged from 25.8 to 27.5%) were not significantly different for the reverse-rotary and C-type rotary tiller. In the dry land tests, the reverse-rotary tiller performed better than the C-type rotary tiller in terms of reduction of shear strength and cone index.