Effects of Tractor Bias-ply Tyre Inflation Pressure on Stress Distribution in Silty Loam Soil

The aim of this paper was to quantify vertical stress distribution in silty loam soil by applying three combinations of tyre inflation pressures of front and rear wheels of a four-wheel drive tractor weighing 3560 kg. The tyres on the tractor were bias-ply, front 11.2-24 and rear 16.9-30, and inflation pressures were 67, 100, and 150% of the recommended pressure. Soil stresses were measured at 10, 30, and 50 cm depths using a stress transducer consisting of ten sensors with a 10 cm distance between sensor centres. Decrease in tyre inflation pressure resulted in a decrease of maximum soil stress at all measured depths. Tyre inflation pressures greatly influenced soil stresses measured in the topsoil. Maximum soil stress in the topsoil depth below front wheel tyres was significantly higher than that below rear wheel tyres. There were no significant differences between tyre contact areas at recommended, high, and low tyre inflation pressures.