The physical effects of two direct drilling coulters on soil beneath and alongside the seed grooves were compared. A triple disc coulter produced more evidence of compactlon at the base of the groove than on the sidewalls. A chisel coulter producd no evidence of compaction in any region. Where initial soil bulk density approximated 1.00 g.cm-3, no effects on root growth resulted from triple disc compactlon. Where initial bulk denSIty was 1.32 g.cm-3, however, the triple disc coulter produced marked effects on early root development of lupin. The chisel coulter did not affect root development at any bulk density. © 1982 Taylor & Francis Group, LLC.