Species-rich hay meadows are usually managed extensively to maintain their biodiversity, with the harvested biomass traditionally being fed to ruminants for milk or meat production. The quality of the biomass is, however, variable, difficult to predict and often does not fulfil today’s requirements. This study established a field trial at two species-rich hay meadows to investigate the combined effect of fertilisation (none, phosphorus and potassium (PK), nitrogen, phosphorus and potassium (NPK)) and date of first cut (at different phenological stages) on biomass quality and quantity. In addition, the most suitable uses of the biomass were explored, including the alternatives biogas and combustion. After four years of the field trial, the stage of maturity at the time of first cut had a greater influence than extensive fertilisation on biomass quality. Dry matter yield (DMY) of the first cut was about 40%–60% of annual DMY (53.99 ± 12.51 dt ha−1 a−1) depending on site, fertilisation and harvest time. Fertilisation had a stronger effect than harvest time on DMY and annual methane yield. In most cases, there was no significant difference in chemical composition between biomass harvested at the end of the grass-flowering stage and at the seed-ripening stage. Thus, a late cut for hay proved to be the most flexible option.

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Biogas production is a key renewable energy pathway for a more sustainable future bioeconomy. However, there is a crucial trade-off between biomass productivity and social-ecological sustainability of available biogas cropping systems. Permanent grassland has been frequently promoted as a promising perennial cropping system for biomass production. Three- and four-cut regimes are usually the highest-yielding and thus preferable for biogas production. A three-year field trial in southwest Germany investigated biomass yield and biochemical composition of mesotrophic Arrhenatheretum grassland under three cutting regimes (two-, three- and four-cut). For the three-cut regime, a preliminary biogas batch test was conducted. The three-cut regime had the highest annual accumulated dry matter yield (11.8–14.8 Mg ha−1), an average specific methane yield of 0.289 m3N kg−1 volatile solids−1 and an accumulated annual methane yield of 3167–3893 m³N ha−1. The four-cut regime performed least favorably due to a lower dry matter yield than the three-cut regime, the highest ash content and the highest nitrogen content. Thus, the three-cut regime promises the best yield performance, whereas the two-cut regime can potentially provide more ecosystem services such as biodiversity conservation and wild-game protection. Consequently, the two-cut regime could help improve the social-ecological sustainability of biogas crop cultivation.

Aims The intensification of grassland management can cause a loss of biodiversity via alteration of the structure and micro‐environmental conditions within the sward. The species richness of hay meadows protected within the Natura 2000 network is often endangered by high levels of fertilisation and relatedly, increased cutting frequency, which leads to decreased light availability for small plants and seedlings at ground level. The purpose of this study is to analyse how management practices and the interaction of fertilisation and cutting regime affect light distribution in grassland canopies as well as the growth of small plants. Location South Germany. Methods This was investigated by measuring the photosynthetically active radiation (PAR) and dry matter yield (DMY) of the first growth cycle over 2 years at two sites of a 5‐year‐old hay meadow trial. To calculate the relative light intensity, PAR was measured above the canopy and at ground level. Two factors, fertilisation (none, PK, NPK) and date of first cut (based on phenological stages), were manipulated. Results Our results show that the date of the first cut had no influence on light availability during the first growth cycle, whereas fertilisation decreased light availability for small plants due to a denser canopy. Fertilisation increased the DMY of the first growth cycle significantly. We show that NPK fertilisation (35 kg N, 35 kg P2O5 and 120 kg K2O ha−1 a−1) decreased both the number and proportion of small plant species. Conclusion NPK fertilisation can lead to a loss of biodiversity. These results are of relevance for the improvement and management of species‐rich hay meadows. Because of its effect on competition for light, the supply of plant‐available nitrogen is a key driver in obtaining or restoring biodiversity in species‐rich hay meadows. Therefore, careful site‐adapted fertilisation is a basic requirement in maintaining the ecological value of grassland.