Effects of tractor passes on the physical properties of an Oxisol in the Brazilian Amazon

Abstract

A field experiment was established on a heavy clayey Oxisol in the Amazon region near Manaus, Brazil, to compare the effect of wheeled tractor passes, with both normal wheel movement and slipping movements, on soil physical properties. Large changes in topsoil thickness were observed; mechanical impedance and dry bulk density were significantly increased, and soil moisture content, porosity and infiltration rate were reduced by these movements. The results suggest that it might be possible to determine an optimum (i.e. minimum structural deterioration) soil moisture state for tractor pass operations involving normal movement, but that the damage caused by slipping occurs independently of soil moisture state.