Humic acids‐based biostimulants impact on root viability and hormone metabolism in creeping bentgrass putting greens

Creeping bentgrass putting greens experience quality decline during summer due to heat and drought stress in U.S. transition zone other areas with similar climate. Plant biostimulants have been used improve turfgrass tolerance abiotic stress. This study was designed investigate the effect modes of action humic acid (HA) based on turf quality, root viability, hormone metabolism creeping The two formulations – solid powder liquid, were characterized applied at rates each formulation a green from May through August this study. Auxin indole-3-butyric (IBA) served as positive control. Foliar application either or liquid HA 0.2% 0.3% biweekly improved photochemical efficiency chlorophyll content certain sampling dates. treatments also increased leaf growth cytokinin zeatin riboside (ZR) July 25 22 auxin indole-3-acetic (IAA) 22. length, surface area (SA), volume, biomass, viability. Solid (HA-S) 0.2%, solution, (HA-L) viability by 91.8%, 122.4%, 57.1%, 71.4%, respectively, when compared suggests foliar acid-based may be considered an effective tool performance months.