Effect of rear tyre dimensions of tractors and tractor traffic in potato cultivation

Abstract

In experiments with different rear wheel tyre sizes of tractors for cultivation work in potato fields, two passes of tractor wheels for each cultivation brought about a decrease in yield as compared with a single pass. Different sizes of rear tyres did not appear to have a marked effect on potato yields. Tractor traffic when spraying against the potato blight in the later part of summer decreased the yield of tubers. In three experiments cultivation by hand resulted in higher yields than tractor cultivation. Soil physical investigations showed the total porosity of the soil to be lower after two passes of tractor wheels than after a single pass. There were no pronounced differences between tyre size treatments, however. The air porosity at a depth of 10–15 cm under the wheel tracks was lower for a tractor with a disc implement than with a tined one, and lower in the furrows than in the ridges. There was an almost linear increase in slip with increasing gradient, and a higher slip for the 11 × 28 in than for the 9 × 36 in tyre. At steeper gradients, it was not possible to measure the slip of the 6 × 36 in tyre on account of digging into the ground. A pronounced sideways sliding of the tractor with 6 × 36 in tyres was observed where the row direction was at an angle to the fall of the land.