Energy requirements and depth stability of two different moldboard plow bottoms in a heavy clay soil

A field experiment was conducted in Saint-Simon (Quebec) on heavy clay soil to establish the difference in energy requirements and plowing depth stability between two plow bottom shapes commonly used. The experimental design was a split-split plot with two bottom shapes, five plowing depths and five speeds. The helical (long) bottom featured lower share and moldboard approach angles than the cylindrical (short) model and it was equipped with a sharepoint and a longer landside. Results indicate that the long bottom reduced the specific draft force (D-s) by 12% and the fuel consumption by 6% relative to the short model. D-s had a non-linear behavior with plowing depth for both models. Speed had only linear effects on D-s for the long model whereas the short bottom displayed both linear, and cubic trends. Plowing depth standard deviation (SD) increased as plowing depth decreased for both bottoms. This trend was less significant for the long bottom. However, the averaged coefficient of variability (CV=SD/mean) for both bottoms increased from 5% to 14% as plowing depth decreased from 220 mm to 140 mm. These results indicate the depth stability problems encountered at plowing depths less than 150 mm.