Winter wheat seeds were grown on compressed soil (a) with and without smearing, (b) with surface horizontal or at 45°, and (c) with and without a sand cover. Germination was not affected. At a soil suction of 0·1 bar, root penetration of the horizontal surface was decreased by smearing and by absence of an overburden; on a surface of 45° smearing had very little effect. As a general summary of the limited information, root penetration is decreased by 50 per cent for a ten-fold increase in suction above 0·1 bar; the effect of smearing is equivalent to a five-fold increase; and the effect of slope is equivalent to a four-fold decrease.