Yield and botanical composition of pastures sown under rape into an ex- Pinus radiata forest block.

Abstract

After the removal of Pinus radiata forests, conditions for establishing pastures are often sub optimal. The ability of rape to aid pasture establishment and suppress weeds was investigated at Darfield, Canterbury between November 2005 and February 2007. The strip plot experiment used pasture grass (perennial ryegrass, tall fescue or cocksfoot) as the main plot and rape sowing rate (0, 0.5 1.5 or 3.0 kg/ha) as the subplot. There was no difference in total pasture yield at the first spring harvest but 50% of the dry matter yield from pastures sown without rape was from weeds compared with 10% in those sown with 1.5 kg/ha of rape. There was no initial yield benefit from rape sown at 3.0 kg/ha compared with 1.5 kg/ha but rape regrowth was greater from the higher rate. White clover was 58% of the total legume yield initially but by February 2007 red clover was dominant (70-95%). In this forestry conversion to pasture, rape sown at 1.5 kg/ha reduced weed encroachment particularly for the tall fescue and cocksfoot which are slow establishing dryland species.