Nitrogen fertiliser dose influence the effect of two year rotational leys with grass or clover- grass on other crops in the rotation

Rotational leys increase yields of subsequent crops. The investigation of long term effects of repeated use of rotational leys in long-term field experiments (LTEs) is often confounded with the effects of animal manure. We used three LTEs situated in southern Sweden to investigate the importance of rotational leys, ley composition and fertiliser regime on grain yield of oats grown as the third crop after incorporation of the leys. We found that 2-year clover/grass and grass leys in 6 year rotations increased yield of oats. At low N regimes, clover/grass leys increase yields more than pure grass leys, but they have similar effect on oats yield when both the grass ley and the oats is fertilised with high doses of N fertiliser. The positive effect of leys on oats yields does not increase continuously over time.