In a practical setup on a 3-yr old nursery green of golf course Bernardus in the southern part of the Netherlands with plots of 1.5 m2 each with 38 commercial varieties of the Dutch seed company Barenbrug in total of 7 different turfgrass (sub)species, varieties of Festuca rubra commutata (Frc), Festuca rubra trichophylla (Frt), Festuca rubra rubra (Frr), Agrostis capillaris (Ac) and Lolium perenne (Lp) were selected for measuring thatch and mat depth. From every variety 8 samples from a plot were taken according to the method described in Evers et al (2024). The construction of the nursery green was a USGA coarse textured sand based construction. The nursery green was maintained like the greens in the 18-holes course, with daily mowing at 5 mm, low nitrogen input (50 kg N ha-1 year-1), regular sand dressing and aeration. In a 4-yr pot experiment thatch thickness in monocultures of different Festuca rubra subspecies and 3 varieties per subspecies in three different mixtures of these varieties of monocultures of Festuca rubra subspecies under low input management, (30 and 90 kg N ha-1.year-1 and no disturbance by sand dressing or aeration, was analysed. Given the possible synergistic effects between subspecies and their varieties on plant biomass production, it was interesting to compare actual measured thatch thickness and visible plant biomass (VPB) concentration in thatch with values that might be expected, calculated based on their monocultures and their relative abundance.

ThatchVPBmixtures.csv Collumns: spec = subspecies or mixture var = variety rep = replicat number Nfert = N fertilizer at 30 or 90 kg ha-1.year-1 thatch1 = thatch VPB at 18-5-2018 (mg dry matter cm-3) thatch2 = thatch thickness at 26-10-2018 (mg dry matter cm-3) thatch3 = thatch thickness at 17-5-2019 (mg dry matter cm-3) thatch4 = thatch thickness at 29-10-2019 (mg dry matter cm-3) thatch5 = thatch thickness at 10-6-2020 (mg dry matter cm-3) thatch6 = thatch thickness at 16-6-2021 (mg dry matter cm-3) Mixtures: mix 1 = 60% Barlineaus + 40% Barcrown mix2 = 40% BargreenII + 60% Barpearl mix3 = 50% FRC234 + 30% Sprinkler + 20% Bardance

Thatchthicknessmixtures.csv results at 30 kg N ha-1.year-1 Collumns: spec = subspecies or mixture var = variety rep = replicat number thatch1 = thatch thickness at 18-5-2018 (cm) thatch2 = thatch thickness at 26-10-2018 (cm) thatch3 = thatch thickness at 17-5-2019 (cm) thatch4 = thatch thickness at 29-10-2019 (cm) thatch5 = thatch thickness at 10-6-2020 (cm) thatch6 = thatch thickness at 16-6-2021 (cm Mixtures: mix 1 = 60% Barlineaus + 40% Barcrown mix2 = 40% BargreenII + 60% Barpearl mix3 = 50% FRC234 + 30% Sprinkler + 20% Bardance

ThatchMatthickness.csv Data from practical setup with following collumns: spec = (sub)species var = variety rep = replicate number thatch = thatch thickness (cm) mat = mat thickness (cm)