Can higher legume diversity reduce clover soil fatigue?

Summary

White clover soil fatigue is an increasing problem in Danish organic dairy farms. The clover cyst nematode (Heterodera trifolii) has been found to play a major role in the problem. Grassland legume species less readily attacked by H. trifolii and less favourable for its reproduction than white clover may offer possibilities for relieving the soil fatigue.
In 2005, screenings were made of nine grass-land legume species / varieties in a field with a rather high level of H. trifolii infestation, pre-cropped with grass/white clover, and in a field with a low infesta-tion level, pre-cropped with maize.
The species grouped in two: 1) White, red, alsike and kura clovers and lucerne had medium to high percentages of nematode attacks and numbers of nematodes pr root, all supported nematode reproduc-tion well, and yields generally were significantly less in the field with higher nematode infestation. 2) Birdsfoot trefoil, black medick and crimson clover had low levels of attacks, few nematodes pr root, and yields were unaffected by field. Only one adult stage nematode occurred in this group (a black medick plant). Hence, this group appeared to be both more resistant to nematode attacks and to support nema-tode reproduction poorly or not at all.