Root Zone Organic Matter Effects on Creeping Bentgrass Growth in Controlled Environments

Turfgrass growth resulting from soil organic matter (SOM) mineralization in putting green root zones has been explored sparingly. Glasshouse and laboratory studies were conducted in Knoxville, TN, USA, to discern if SOM content would result in differential mineralization affecting creeping bentgrass (CBG) ( Agrostis stolonifera L.) growth. Cores (10.8-cm diameter by 10-cm depth) were collected from CBG putting greens varying in SOM content: low (6.4 to 12.6 g·kg −1 ), medium (12.7 to 19.4 g·kg −1 ), and high (19.5 to 25.6 g·kg −1 ). One putting green from each SOM group was selected for further investigation during Aug to Oct 2023. After 8 weeks in the glasshouse, SOM decreased 5 g·kg −1 within cores originating from putting greens in the high and medium SOM groups, compared to only 1 g·kg −1 for those in the low SOM group. Inorganic N within cores from putting greens in the high and medium SOM groups increased more than those from the low SOM group, suggesting a greater percentage of inorganic N was allocated for CBG growth in the glasshouse. When incubated at 25 °C under dark conditions in the laboratory, inorganic N increased 36 mg·kg −1 in cores from the high SOM group, indicating the potential for as much as 50 kg·ha −1 of N to become available within root zones of CBG putting greens. If unaccounted for when making synthetic fertilizer applications, available N from SOM in CBG putting greens could lead to excessive growth under field conditions requiring additional maintenance practices. Future research to confirm this response under field conditions is needed to develop sustainable fertilizer programs supplying N to CBG putting greens.