SOIL CUTTING BY A COMPACT DISC HARROW HAVING VARIOUS DISC ARRANGEMENTS

摘要

The compact disc harrow (CDH) is a relatively new type of conservation tillage implement. The disc arrangement on the implement is critical to the tillage performance. The objective of this study was to investigate the effects of disc spacing and offset on the tillage performance of a CDH. Tests were conducted in an indoor soil bin using a CDH with threedisc units. The spacing of the two rear discs in each unit was set at 203, 254, or 305 mm, and the front discs were set at one of three offset positions (left, center, or right) relative to the rear two discs. The discs were operated at two different tillage depths: shallow (63.5 mm) and deep (127 mm). The results showed that the soil cutting area ratio (the ratio of disturbed area to the total area of the furrow) decreased as the spacing increased from 203 to 305 mm. In contrast, the soil cutting efficiency (the volume of soil cut per unit quantity energy used) remained constant in the shallow tillage depth and increased in the deep tillage depth. As for the effect of offset, the center position resulted in a soil cutting area ratio of more than 80%, which was superior to the other two offset positions. However, the right offset had the highest efficiencies of 15.3 and 22 m(3) MJ(-1) in the shallow and deep tillage depths, respectively. The common standard disc spacing of 254 mm with a center offset was not necessarily the optimal setting, depending on the working depth and tillage performance indicators of interest.