Tilling tests of rotary tiller and power harrow after subsoiling

Abstract

Soil preparation is one of the most energy-consuming activities in plant production. To reduce the operating cost and the soil compaction effect, researchers have tried to decrease the number of machinery passes required for soil preparation, including using a rotary tiller and a power harrow as potential devices to incorporate with a subsoiler. In this study, field tilling tests were conducted using a rotary tiller and a power harrow under with- and without-subsoiling beforehand. The results in the field without subsoiling beforehand showed that both the rotary tiller and power harrow had mean negative drafts of −4.31 and −1.98 kN, respectively. The rotary tiller showed mean negative slip of −1.09% while the power harrow showed mean positive slip of 2.40%. The negative slip implied an amount of surplus thrust to push a tractor moving forward. The rotary tiller generated upward vertical force while the power harrow resulted in downward vertical force. In the field tilling tests after subsoiling, the rotary tiller in the loam soil field still produced a mean negative draft of −1.36 kN and mean negative slip of −0.70%. The power harrow resulted in a mean positive draft of 3.83 kN and mean positive slip of 0.68%. However, with a relatively hard surface of sandy loam soil field, the rotary tiller had a mean positive draft of 1.59 kN and could till down only about a half of its maximum working depth capacity while the power harrow still worked at about its maximum depth. It was observed the bouncing movement of the rotary tiller rather than successful penetration of the soil. The power harrow seemed to produce a smaller mean soil clod diameter than the rotary tiller. The proposed equation may be useful to quantify the amount of surplus thrust generated by the rotary tiller and power harrow; however, further research is needed to improve the fit of the equation to the data.