SOIL PHYSICAL-PROPERTIES AS AFFECTED BY TRAFFIC - SINGLE, DUAL, AND FLOTATION TIRES

Soil compaction from field traffic is a world-wide concern in producti on agriculture. Soils may be especially vulnerable to excessive compac tion during early spring tillage operations when the necessities of ti mely planting often demand decisions to traffic fields at highly susce ptible moisture contents. It is necessary to quantify the soil respons e to typical spring traffic loading to better understand the potential for adverse effects on crop response. For this reason, a 116 kW front -wheel-assist tractor, ballasted to a 6.4 t rear axle load, was operat ed on deep- tilled and moldboard plowed silt loam soil conditions usin g three rear tire configurations: single 18.4R42* radials, dual 18.4R 42* radials and single 66 x 43.00-25 high-flotation tires. Soil physi cal properties measured to a depth of 500 mm showed no significant cha nges due to axle load effects below 250-300 mm. Single and dual tires affected physical properties to a greater depth than did flotation tir es on plowed soil. However, the 6.4 t axle load did not produce excess ive soil compaction compared to the effect of a 27.8 t vehicle.