How type and duration of leys affect carryover nitrogen to following crops is still poorly quantified. We established ten crop rotations to compare effects of: (1) leys during 18 or 30 months; (2) legumes, either as clover in leys or as grain legume; and (3) improved soil cover by catch crops. We assess effects on the yield and N nutrition of the crops, as well as on the N efficiency of the entire crop rotation. At this midstage of the experiment, we compare the effects of a perennial ryegrass-red clover mixture, a pure ryegrass ley, a barley-catch crop and a barley-fallow sequence on the yield of following spring wheat and pea crops. The leys and the barley were established in autumn 2020. In early spring 2022, stands were terminated to plant either wheat or peas. Wheat yield following grass-clover ley was on average 46% larger than following barley or pure grass. Pure grass did not benefit wheat yield compared to barley. After a single catch crop period, the effect of improved soil cover was trending beneficial for both peas and wheat, but differences were not significant. We conclude from these preliminary results that grass-clover is a clearly superior preceding crop for spring wheat compared to pure grass or barley.
