Effect of Bacillus sp. N188 application on turf quality and functional value

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Maintaining high-quality functional and recreational turfgrass requires effective management practices that support turf performance under field conditions. One promising strategy involves the use of plant growth-promoting microorganisms. The aim of this study was to evaluate the effect of Bacillus sp. N188 on turf quality and functional performance. A field experiment was conducted in 2024–2025 under the conditions of southern Poland on Haplic Phaeozem soil. The study included two lawn mixtures differing in species composition and intended use: “Uniwersalna U-1” and “Super Trawnik”. The experimental design comprised control treatments and variants with annual application of a preparation containing Bacillus sp. N188. Turf quality was assessed according to the COBORU methodology, including visual traits (overall appearance, turf density, leaf colour and structure, and disease susceptibility), as well as physiological indices (NDVI, LAI, SPAD) and selected indicators of functional value. The application of Bacillus sp. N188 significantly improved turf quality compared to the control treatments. An increase in sward density and uniformity, more intense leaf coloration, improved structural characteristics, and reduced incidence of fungal diseases were observed. The physiological indices confirmed improved plant condition in plots treated with the bacterial preparation. The positive effects of Bacillus sp. N188 were observed in both lawn mixtures, although the magnitude of the response varied depending on species composition. The results indicate that Bacillus sp. N188 has potential as a plant biostimulant for improving the aesthetic and functional properties of turfgrass under temperate climatic conditions.