Abstract
This research included studying two disc angles for front gangs of tandem disc harrow 15 and 22 degrees with three ground speeds 8.166 , 10.378 and 16.354 kmhr in tilth soil and 9.587, 12.473 and 16.000 kmhr in untilled soil , disc angle of rear gangs was fixed at 22 degree , and effect of these factors on fuel consumption, slippage percentage, number of soil aggregates larger than 5 cm/m2, cutting depth, cutting width, coefficient of cutting width, line width lifting behind rear gangs and effective field capacity. Soil state had significant effects on number of soil aggregates larger than 5 cm/m2, cutting depth and line width lifting behind rear gangs, Ground speed and disc angle had significant effects on slippage percentage, cutting depth and effective field capacity. The effect of interaction between soil state and disc angle was significant in slippage percentage and effective field capacity. The effect of interaction between soil state, disc angle and ground speed was significant in effective field capacity, while ground speed treatment with disc angle and soil state had no significantly effect in studied characteristics.
