THE INFLUENCE OF SOIL FACTORS ON THE GROWTH OF A GRASS CLOVER SWARD ON A RESTORED OPENCAST SITE IN NORTHUMBERLAND, UK

The growth of grass and clover components in mixed swards on a site re stored after opencast coal mining and an undisturbed control site were compared. Soil nitrogen supply was reduced at the restored site. This inhibited grass growth but was beneficial for the clover component. G rowth at the restored site was also inhibited by a compacted subsoil, which reduced available soil water content and impeded access to avail able soil water. This inhibited crop production from the middle of the second silage crop onwards. In 1989 this was associated with the soil at the restored site reaching permanent wilting point at 40 cm. In 19 90 this effect was associated with the restored site soil reaching per manent wilting point at 70 cm. These drought effects reduced clover gr owing point population and stolon mass. Grass tiller populations were unaffected.