اثر عمق و زاويه حمله بر مقاومت كششي زيرشكن تيغه مورب

The Effect of Depth and Rake Angle on Draft Force in an Oblique Blade Subsoiler

Rake or penetration angle of tillage tools, causes downward suction in the soil. Choosing a suitable rake angle in a tillag tool is necessary for reducing draft force, while maintaining proper penetration. A field experiment was conducted to evaluate performance of depth and rake angle in an oblique blade subsoiler in Fars Agricultural Research Center, Zarghan. A randomized complete block design, as spilt plot factorial was employed to investigate the effect of rake angle (as subplot) at four levels (7.5, 15, 22.5 and 30 degrees) and working depth (as main plot), at three levels (250, 350 and 450 mm) with three replications. The soil was of clay loam texture with 10% moisture content d.b. Draft, soil cross sectional area disturbed and cone indices were considered as experiment variables. Tractor forward speed was maintained at constant level of 3.5 kmh^-1 in all treatments. Analysis of results indicated that working depth and rake angle had significant effects at 1% probability level on draft force. Draft force increased with increasing working depth as well as rake angle. Working depth had a positive effect on increasing disturbed soil cross sectional area but a negative effect on cone indices; furthermore, rake angle was observed to have no significant effect on these variables. Mean values indicated that there was no significant difference between rake angles of 7.5 and 15 degrees and since oblique blade subsoiler was demonstrated to have a better penetration in raking angle of 15 degrees, this angle was chosen as the optimum.