Mechanical and cropping behavior of direct drilled soil under different traffic intensities:: effect on soybean (Glycine max L.) yields

The effect of different traffic intensities on soil physical properties and soybean (Glycine max L.) yields under a direct drill system were compared in the western part of the Rolling Pampas Region. The traffic intensity treatments were 0, 60, 120 and 180 Ma km ha(-1), applied using a tractor in the same track in a soybean crop. The tractor used was a 2WD with a 102.6 kW engine and 39.38 kN total mass, equipped with 7.50-16 lyres on the front axle and 23.1-30 tyres on the rear axle. Five months later, the soybean yield was evaluated in the tractor track areas and yields decreases in the range 9.8-38%, were measured. Yield reductions of 38, 22.6 and 9.8% occurred under the 180, 120 and 60 Mg km ha(-1) traffic intensities treatments, respectively. Measurements of soil penetration resistance, bulk density and rut depth, gave an indication of the soil compaction due to tractor traffic. (C) 2004 Elsevier B.V. All rights reserved.