Effect of Calcium and Nitrogen Fertilizer on Creeping Bentgrass (Agrostis stolonifera L.) Plant Growth and Tolerance to Dollar Spot (Sclerotinia homoeocarpa (Bennett) Under Low Temperature.

Creeping bentgrass (Agrostis stolonifera) remains the most desirable cool-season grass used on putting greens in the transition zone of the United States. It provides a superiorly smooth and uniform putting surface due to its year-round color and fine leaf texture. Despite these desirable traits, creeping bentgrass is susceptible to dollar spot, caused by fungal pathogen S. homoeocarpa. In Missouri, dollar spot can become active as early as March, and symptoms can last for the entire growing season till the beginning of November. In central Missouri, average temperatures in March are between 0.6 and 12.7 ℃ for low and high temperatures, respectively. During this period, creeping bentgrass starts to regrow, and the first fertilization in spring typically occurs in March as well. Nitrogen fertilization has been reported to mask dollar spot symptoms, and our earlier experiment indicated that calcium fertilizer enhances creeping bentgrass’s tolerance to dollar spot as well. Therefore, the objective of this experiment was to assess possible interaction of nitrogen and/or calcium fertilizer and cool temperature and their influence on creeping bentgrass for its tolerance to dollar spot. A growth chamber experiment will be performed and treatments, including with or without calcium fertilizer, with or without nitrogen fertilizer, and with or without inoculation of S. homoeocarpa, will be arranged in a 2 x 2 x 2 factorial combination in a completely randomized design with five replications. Creeping bentgrass core samples (7.6 cm diameter) collected from a USGA green will be transplanted into cone-tainers (7.6 cm diameter and 35.6 cm depth) filled with USGA-spec sand before subjected to 4 ℃ growth condition after acclimations. During the experiment, plants will be maintained at 2.5 cm and watered daily to prevent drought. Data collected will include weekly assessment of turf quality based on a 1-9 scale, percent green cover using digital images and WinRhizo analysis, clipping biomass at 1, 2 and 3 weeks after treatment application, and weekly percent disease coverage throughout this experiment. At the end of the study, the shoot and root biomass will be collected as well. This is an ongoing experiment; more data will be discussed during the presentation.