The effect of nitrogen level and time of sowing on the establishment of white clover ( Tripolium repens) on colliery spoil

Abstract

Methods of establishing white clover ( Trifolium repens) on colliery spoil were investigated in a 2-year greenhouse experiment by varying nitrogen fertiliser levels and clover sowing times with respect to those of companion Lolium perenne. Clover established best at the lowest nitrogen levels when sown with the grass. When sown into established grass swards, best clover growth occurred after the spoil nitrogen supply had become depleted. As mineralisable nitrogen levels in the spoil fell, white clover became dominant, even in swards where it had initially established poorly. In the second growing season, herbage yield was equivalent to 1320 g DM m -2, of which 90% was white clover. Mineralisable nitrogen levels were still very low. It is suggested that this is because most of the nitrogen fixed (estimated at # 40 g N m -2) was utilised by the clover in shoot growth and was removed at harvests.