Effect of mowing versus abandonment of mesic grasslands in Central Europe on biomass use for biogas production: Implications for semi-natural ecosystem conservation.

The economic management of lignocellulosic biomass from semi-natural grasslands is now a challenge across Europe. The abandonment of mowing these grasslands leads to the gradual degradation of these ecosystems. This study investigates how chemical and biological factors affect the suitability of biomass from abandoned grasslands for biogas production. We sampled 30 mown and 30 abandoned grassland sites in the Sudetes Mountains (Poland and Czechia). The cover contribution of short herbs was found to be significantly higher in mown grasslands (p < 0.001), while that of tall herbs was more prevalent in abandoned grasslands (p < 0.01). The specific biogas yield (SBY, NL kg-1 volatile solids) is negatively affected by an increased percentage of herbs in the biomass of mown and abandoned grasslands. This is due to the inhibitory effect of herbs on biodegradation, the increase in lignin content and the decrease in cellulose. This study highlights the importance of individual plant species in assessing grassland biomass for area biogas yield (ABY, m3 ha-1) and provides new insights into a field that has not yet been extensively investigated. In mown grasslands, ABY was most positively correlated with grass species (Arrhenatherum elatius, Trisetum flavescens and Festuca pratensis). In abandoned grasslands, the ABY was most correlated with herbaceous species (Galium aparine, Urtica dioica and Chaerophyllum aromaticum) and grasses (A. elatius and Elymus repens). Mown grasslands had significantly higher species richness (p < 0.001) compared to abandoned grasslands, but the number of species sampled did not correlate with SBY and ABY. This study contributes to the development of a sustainable bio-economy by highlighting the need for efficient use of grassland biomass. This approach helps protect semi-natural ecosystems and facilitates sustainable management of renewable resources.

The Admont Grassland Experiment: 70 years of fertilizer application and its effects on soil and vegetation properties in an alluvial meadow managed under a three-cut regime.

Fertilizer application is a widely used management technique for increasing forage production from agricultural grassland. Fertilization is also a key driver of changes in soil nutrient status and plant species composition of grassland as shown in many short-term studies. Results from long-term experiments can further improve understanding of plant-soil relationships and help with management recommendations for agricultural and environmental outcomes. We collected data from a long-term experiment on alluvial meadow (Admont Grassland Experiment, Austria; established 1946) with 24 fertilization treatments managed under a three-cut regime. Soil sampling in autumn 2015 and vegetation sampling in spring 2016 were conducted in seven selected treatments. Combinations of N (nitrogen 80 kg ha-1), P (phosphorus 35 kg ha-1) and K (potassium 100 kg ha-1) were applied annually and compared with a non-fertilized control. Treatments were: Control, N, P, K, NP, NK, PK and NPK fertilization. Long-term different fertilization affected soil pH and nutrient concentrations in the soil and plant species composition, but no significant effects on species richness were found. Short species (<0.5 m height) prevailed in all treatments regardless of nutrient application, probably as a result of the three-cut defoliation. The dry matter biomass (DMB) yield in the Control was limited by N and P and synergisticly co-limited by N, P and K, and DMB yields of more than 5 t ha-1 per year were achieved under nutrient combinations containing P (NP, PK, NPK) without loss of species richness. Results from the Admont Grassland Experiment show that the tested nutrient combinations significantly increased DMB yield and changed the species composition, but without significant effects on species richness. Long-term biomass yields of more than 5 t ha-1 DMB per year can be achieved with any nutrient combination containing P without loss species richness in an alluvial meadow managed under a three-cut regime.