Development of a low input system for growing wheat (Triticum vulgare) in a permanent understorey of white clover (Trifolium repens)

Summary In three field experiments carried out during 1989‐91, a permanent sward of pure white clover (Trifolium repens) was established to provide a source of N for winter or spring wheat crops (Triticum vulgare) directly drilled into the legume. Spring‐sown wheat failed to compete with the clover, but wheat sown in the autumn established successfully. N fertiliser was applied to all three experiments at rates of 0, 50 and 100 kg N ha“ 1 measurements of grain and whole‐crop silage yields were made. Yields were low for all treatments, probably because of the dry conditions prevailing and the low soil N status of the site used. Yield responses to fertiliser were significant, despite the contribution to plant nutrition that the clover was intended to make. A key feature of the work was that the clover survived successive cereal crops and could be grazed and used as an understorey for later crops. Further, response to fertiliser N diminished with a successive crop implying a build‐up of available soil N, which measurements confirmed had occurred. Use of the system obviated the need to use pesticides, although reasons for the lack of pest damage were not clear.