In situ quantification of forage grass root biomass, distribution and diameter classes under two N fertilisation rates

Roots are of paramount importance in protecting grassland in numerous ecosystem services e.g. soil organic matter build-up. However, studies that quantified root biomass in grasslands predominantly focused on areas managed less intensively than the management that is common to most North-West European grassland-based farms. To fill this knowledge gap, we compared, root and stubble biomass, the distribution in the soil and root diameter classes of five common European forage grass species grown under intensive management. On a 3 year old trial comparing yield of five cool season forage grass species at two N fertilization levels (190 kg N ha(-1) yr(-1) or 300 kg N ha(-1) yr(-1)) we sampled root and stubble biomass until a depth of 90 cm deep. Tall fescue (Festuca arundinacea) displayed the highest root and stubble biomass and had the highest mean root diameters of all studied grass species. The total dry biomass below cutting height (stubble + roots up to a depth of 90 cm below the soil surface) varied between 18 and 19 tonnes ha(-1) for tall fescue and 10 and 11 tonnes ha(-1) for Festulolium at 190 kg N ha(-1) yr(-1) and 300 kg N ha(-1) yr(-1), respectively. Our findings emphasize that in intensively managed grassland, root and stubble biomass under a 3 years old sward can be as high as 19 t DM ha(-1). Owing to the high forage and root biomass of tall fescue, this species has a high potential in maintaining several ecosystem services.