SOIL PHYSICAL PROPERTIES AND INFILTRATION RATE AS AFFECTED BY TIRE DYNAMIC LOAD AND INFLATION PRESSURE

Abstract

Wheel traffic of agricultural prime movers is a major contributor to detrimental soil compaction. Soil response to differences in tire inflation pressure and vertical load was determined beneath 18.4 R34 rear drive tires on a two-wheel-drive tractor which had the centerline of each rear tire 520 mm laterally outboard of the centerline of itscorresponding front tire. No drawbar load was applied to the tractor. The tires were used with two static loads (12.5 and 21 kN) and three inflation pressures (193, 124, and 76 kPa). Inflation pressures recommended by the tire manufacturer were 40 kPa for the 12.5 kN load and 105 kPa for the 21 kN load. Soil bulk density and cone index generally increasedand air-filled porosity generally decreased in the 100 to 500 mm depth range beneath the tire centerline as the static load increased and as inflation pressure increased. Water infiltration rate into soil at the tire track centerline generally decreased as the static load increased and as inflation pressure increased.