Kentucky bluegrass and bermudagrass rooting response to humic fertilizers during greenhouse establishment

Greenhouse research was conducted to examine effects of adding humic products to fertilizers on turfgrass. The objective of this study was to determine if the addition of humic products to fertilizers will increase turfgrass root and shoot morphological parameters. Kentucky bluegrass (KBG; Poa pratensis L.) and bermudagrass [Cynodon dactylon (L.) Pers.] were established in sand‐filled tubes. Treatments included synthetic fertilizer with black gypsum (22N‐0P‐3.3K, 30% gypsum and 4.7% humic acid), polymer‐coated humic‐coated urea (PCHCU; 2% humic acid), urea with humic dispersing granules (HDG; 70% humic acid), starter fertilizer (18N‐10.5P‐10K) with HDG, starter fertilizer, stabilized nitrogen, urea, and a control group. Fertilizers were applied at 48.8 kg N ha−1 and HDG was applied at 44.4 kg ha−1. Starter fertilizer and starter fertilizer with HDG increased KBG total root length (105 and 112%), root biomass (232 and 244%), and shoot biomass (205 and 204%) compared with urea. In KBG, PCHCU and urea with HDG increased total root length (37 and 20%) compared with urea. In bermudagrass, starter fertilizer and starter fertilizer with HDG increased total root length (241 and 248%), root biomass (672 and 707%), and shoot biomass (821 and 808%) relative to urea. Besides treatments with starter fertilizer, no treatments were different from urea for bermudagrass. These results suggest that starter fertilizer application is critical to turfgrass rooting at establishment. Adding humic products to the starter fertilizer did not increase rooting. In the absence of a starter fertilizer, PCHCU and urea with HDG improved KBG total root length compared with urea.