Turfgrass performance during dormancy period and spring green-up of bermudagrass cultivars under biostimulant programs in two Mediterranean regions

The use of biostimulants in turfgrass management has been growing to reduce chemical fertilizers, with the goal of healthier and more resilient turfgrass. This study investigates the performance of three bermudagrass cultivars (Arden 15, Princess 77, and Sultan) under different biostimulant-based programs in two Mediterranean locations (Valencia, Spain; Legnaro, Italy) over two years. The research focused on turfgrass quality, color, NDVI, green cover, and stolon carbohydrate reserves during autumn dormancy and spring green-up periods. Climate significantly influenced bermudagrass performance, with a shorter dormancy period in Spain compared to Italy. Princess 77 showed higher quality and color ratings during warmer months, slower color loss approaching dormancy, and delayed spring green-up, especially in Italy. Arden 15 and Sultan performed similarly throughout the study, with Arden 15 showing good spring green-up in Italy. The biostimulant Hicure had a limited impact on overall turfgrass quality, with modest improvements observed mainly in Spain for Arden 15. Stolon carbohydrate analysis revealed that Princess 77 had lower starch content in early spring, particularly in Italy, suggesting greater carbohydrate utilization during winter. Bermudagrass performance is primarily influenced by cultivar adaptability to local climate conditions, with temperature being a critical factor affecting dormancy, green-up, and stolon carbohydrate reserves. The biostimulant Hicure showed limited effectiveness in extending the vegetative period or promoting spring green-up compared to traditional urea fertilization.