A number of techniques are described which sought to characterise the physical effects of coulter passage on the soil beneath and to the side of direct-drilled grooves. Measurements were made of the instantaneous and permanent soil deflection and of the zone of influence of individual coulters. No single measurement was considered to be wholly representative but collectively, data obtained from pressure sensing, bulk density, and penetrometer instruments agreed well. These were also supported by photography and electron-microscopy. © 1982 Taylor & Francis Group, LLC.