Summer droughts reduce forage yield and quality in mountain grasslands. This study aimed to determine the most suitable multi-species mixtures that provide satisfactory yield and quality under drought, yet performing well under optimal rainfall conditions. To this end, in 2023 we sowed nine multi-species mixtures differing in dominant species identity (Dactylis glomerata, Alopecurus pratensis, co-dominance of both) and expected proportion of drought-resistant species (0, 15, 30% DRsp) including Plantago lanceolata, Lotus corniculatus, Festuca rubra, Agrostis capillaris in a mountain site (1115 m, Switzerland). The experiment followed a split-plot design with the nine mixtures growing under either control or drought conditions with four replicates. Drought was simulated during the year after sowing using rainout shelters excluding all precipitation during 7 weeks in summer. Yield decreased for all mixtures under drought (up to 48%), but it was less severe for the mixtures with DRsp. In both drought and control conditions, yield and acid detergent lignin (ADL) content of the second regrowth increased with increasing DRsp abundance, while crude protein (CP) and neutral detergent fibre (NDF) decreased. Within the same climatic conditions, the annual yield was similar among the different mixtures.
