Combining wheat with fodder legumes in organic cereal farming systems: a solution for weed control and nitrogen nutrition in crops

Organic cereal farming systems need to be adapted to cope with nitrogen deficiencies and the challenges of weed control. This is all the more true when they specialise in arable crops and when fodder legumes – despite being a promising solution to these problems – are under-represented in crop rotations. Our study examined the intercropping of four species of legume cover crops under winter wheat to provide a combined solution to weed management and crop nitrogen nutrition. The cover crops were maintained after the cereal harvest until the subsequent maize sowing. The performance of both the cash crops and the legumes was monitored, as were weed development and nitrogen dynamics within the soil-plant system. Our results showed that minette and red clover, which tolerated competition from the wheat best, were likely to reduce the protein content of the grains (–0.3 to –0.4 per cent). However, the cover legumes did not affect wheat yield. Furthermore, all four species proved effective at controlling weeds, both during the intercropping period and in the subsequent crop. Finally, nitrogen return to the subsequent maize crop was effective and resulted in a significant 30 per cent increase in grain yield.