Soil stresses and rut depths from tires of a mechanical front wheel drive tractor

Soil stresses were determined just above a hardpan beneath the centerlines of tires representative of front and rear tires of a mechanical front wheel drive (MFWD) tractor with dual rear tires. Rut depths were measured at the centerline of each tire track. A 14.9R30 R-1 front tire and an 18.4R42 R-1 rear tire were operated on a sandy loam and a clay loam soil with loose soil above hardpans in soil bins, using three combinations of dynamic load and inflation pressure representative of a tractor hitched to a row-crop planter. When a tractor of this type is used with either an integral planter with liquid chemical carried on the tractor, or a towed planter without liquid chemical carried on the tractor, the front tires cause greater soil stresses and rut depths than the rear, so the front tires are likely to compact the soil more than the rear tractor tires. A tractor configured for use with a towed planter without liquid chemical carried on the tractor generates lesser soil stresses and rut depths, and therefore is less likely to compact soil beneath the tractor tires than a tractor configured for an integral planter with liquid chemical carried on the tractor.