Turfgrass with sand‐based root zones, such as golf course putting greens, are highly important economically and require intense management. However, problems are often associated with sand‐based root zones, such as low nutrient retention and limited microbial activity. Soil additives may increase soil biological activity, improve nitrogen (N) cycling efficiency, and thus reduce fertilizer N inputs. A 2‐yr experiment was conducted on a sand‐based creeping bentgrass (Agrostis stolonifera L.) putting green to investigate whether humic products could increase soil biological activity and improve turfgrass quality. Treatments included humic‐coated urea (HCU; 2/3 rate and full rate), HCU + humic dispersing granules (HDG), HCU + black gypsum (BG), urea, HDG, and a nontreated control. Minimal differences were seen in microbial biomass and activity besides HCU + BG. The HCU + BG had 60% greater potentially net N mineralization relative to the HDG and the nontreated control. Overall, incorporating humic substances with N fertilizer did not increase turfgrass quality, cover, and clipping biomass compared with N fertilizer alone. However, the addition of BG to N fertilizer enhanced microbial activity (i.e., potentially net N mineralization).