The effect of oscillation angle on the performance of oscillatory tillage

In established Australian vineyards compacted soil either created naturally or by trafficking prevents root growth to desirable depths and restricts root systems from getting water and nutrients. This can reduce the life span and productivity of grapevines considerably over a period of years. To break up these compacted soil layers using small tractors a deep working oscillatory ripper was developed at the University of South Australia which had two deep working oscillating tines. One of the most important factors for the performance of this oscillatory ripper is the oscillation angle of the tines. To find the optimum oscillation angle a series of field tests were conducted in a sand-loam soil at six different oscillation angles. The tines oscillated at a frequency of 4.9 Hz and with amplitudes of between +/-60 and 69 mm, with a nominal forward speed of 3 km/h. The trial results were quantified as draft requirement, power saving, power ratio, loosened area and amount of vibration on tractor seat. The greatest draft reduction of 50% was achieved for negative oscillation angles, where power ratio was less than 1. Power saving was significantly affected by changing oscillation angle. In general, vibration of the driver seat was higher for negative angles. In terms of performance -22.5 degrees oscillation angle was the optimum for draft reduction and power saving, whereas the least vibration was obtained at an oscillation angle of +16 degrees which was equal to Australian Standard threshold for 8 h continuous work. (C) 2009 Elsevier B.V. All rights reserved.