30In repeatedly mown and mulched green manure leys, the mulched herbage contains substantial amounts of 31 nitrogen (N), which may only slightly contribute to the following crops´ nutrient demand. The objective of the 32 present work was to evaluate the effect of alternative strategies for green manure management on the yield and N 33 recovery of a subsequent spring barley crop, and their short term effects on soil structure and earthworm 34 populations. A field trial was run from 2008 to 2011 at four sites with contrasting soils under cold climate 35 conditions. We compared several options for on-site herbage management and the application of anaerobically 36 digested green manure herbage. Depending on the site, removal of green manure herbage reduced the barley 37 grain yield by 0% to 33% compared to leaving it on-site. Applying digestate, containing 45% of the N in 38 harvested herbage, as fertilizer for barley gave the same yields as when all herbage was mulched the preceding 39 season. Overall, the apparent N recovery was enhanced from 7% when all herbage was mulched, to 16% when 40 returned as digestate. A positive effect on earthworm density and biomass was seen after one season of retaining 41 mulch material, rather than removing it. Digestate did not affect the earthworm population, but contributed to 42 higher soil aggregate stability. In conclusion, for spring barley production after green manure ley, the digestate 80In spring barley, availability of inorganic N at the early tillering stage is a key factor for N uptake and 86alternative strategies appear to be necessary. Application of digestate from green manure foliage digested 87anaerobically in a biogas plant may be a promising option for improving yields and N recovery instead of 88 mulching (Möller and Müller, 2012;Stinner et al., 2008). In biogas plants, the easily degradable organic matter 89

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Four‐species mixtures and pure stands of perennial ryegrass, tall fescue, white clover and red clover were grown in three‐cut and five‐cut systems at Ås, southern Norway, at a low fertilization rate (100 kg N ha−1 year−1). Over a three‐year experiment, we found strong positive effects of species diversity on annual dry‐matter yield and yield stability under both cutting frequencies. The overyielding in mixtures relative to pure stands was highest in the five‐cut system and in the second year. Among the possible pairwise species interaction effects contributing to the diversity effect, the grass–grass interaction was the strongest, being significant in both cutting systems and in all years. The grass–legume interactions were sometimes significant, but no significant legume–legume interaction could be detected. Competitive relationships between species varied from year to year and also between cutting systems. Estimations based on species identity effects and pair‐specific interactions suggested that the optimal proportions of red clover, white clover, perennial ryegrass and tall fescue in seed mixtures would have been around 0·1, 0·2, 0·4 and 0·3 in the three‐cut system, and 0·1, 0·3, 0·3 and 0·3 in the five‐cut system.

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