Hardsetting and structural regeneration in two unstable British sandy loams and their influence on crop growth

Soil bulk density, penetration resistance, and cabbage shoot and root growth were compared on two structurally unstable sandy loams. Both soils slumped after mouldboard ploughing but in one, structural regeneration occurred, roots grew down cracks and had penetrated below 0.5 m at 5 weeks after transplanting. No structural regeneration occurred in the other soil which shrank uniaxially and set hard. This increased resistance to cone penetration sufficiently to retard root growth severely. Roots penetrated no deeper than 0.3 m in the same period. At 5 weeks, cabbages were almost twice as heavy on the better than on the worse soil but this difference disappeared by harvest. The reasons why the soils behaved differently is linked to the differences in organic matter content and the periods of time that each soil has been under cultivation. © 1991.