The effect of harvest, mulching and low-dose fertilization of liquid digestate on above ground biomass yield and diversity of lower mountain semi-natural grasslands

• Low-dose fertilization and mulching increased productivity in short terms.
• Considering biodiversity, low dose fertilization and harvesting is preferable to mulching.
• Low-dose fertilization did not decrease species number.
• Fertilization led to changes in plant community composition.

The effect of the biomass conversion system called integrated production of solid fuel and biogas from biomass (IFBB) on above ground biomass yield and diversity in semi-natural grasslands of lower mountain ranges was investigated over a time span of 5 years. The system uses late cut grassland biomasses and produces energy carriers and a liquid fertilizer, the effect of which was tested against the alternative of harvest without fertilization and mulching without fertilization. The biomass yield significantly improved both in fertilized and mulched treatments, whereas it remained low in the unfertilized treatment. The effects on diversity were less explicit. Species numbers remained stable in the fertilized and unfertilized cutting treatment and decreased in the mulching treatment. The applied treatment showed no significant effect on diversity indices (H′, E and T). Mean Ellenberg indicator values for nutrients revealed that species accustomed to nutrient poor habitats increased in the unfertilized cut treatment and decreased in the fertilized and mulched treatment.