A Survey of Organic Matter Concentration in Creeping Bentgrass (Agrostis palustris Huds.) Putting Greens in the Continental US.

Organic matter in creeping bentgrass putting greens has become an increasing concern during the last 20 years. Cultural practices such as soil cultivation and sand topdressing have been commonly used to manage OM accumulation in putting green. The objectives of this study were to (1) develop a regression model to predict OM concentrations in golf course putting greens; and (2) determine cultural practices that are most effective in controlling increased OM concentrations. One hundred and four golf courses in 15 states were surveyed for cultural practices and OM content. Models were fitted by examining bivariate relationships between OM concentration, and variables of interest. Variables that caused significant differences in OM concentrations were entered into multivariate linear regression models using backward, forward, and stepwise selection procedures to construct the final model. Variables in the final model included cultivar, sand topdressing frequency, cultivation frequency, and putting green age. Golf course greens with unknown cultivars had significantly higher OM concentrations then golf courses with known cultivars, like ‘Penncross', ‘Providence', ‘Dominant', ‘Pennlinks', ‘L93', ‘Penn A or G series'. Sites that used topdressing every 7 to 14 days had significantly lower OM content than those that topdressed greens monthly, and once or twice yearly. Sites that received autumn cultivation only had significantly higher OM concentration than those that cultivated monthly. As greens aged, OM concentration increased at a yearly rate of 0.3 g kg-1, regardless of cultural practices used. When used as a prediction equation, the fit of the regression model was statistically weak, which supports the complexity of the parameters involved in OM concentration in creeping bentgrass putting greens. Cultural practices, such as frequent topdressing and soil cultivation timing, were identified as consistent factors that reduced OM concentrations.