Organic Matter Concentration of Creeping Bentgrass Putting Greens in the Continental U.S. and Resident Management Impact

Soil organic matter (SOM) accumulation in creeping bentgrass (Agrostis stolonifera L.; CB) putting greens has been a concern for decades. Gaussoin et al. (2013) summarized the negative effects associated with excessive SOM (thatch-mat), including decreased water infiltration, localized dry spots, reduced high and low temperature tolerances, increased pest problems, and reduced pesticide effectiveness. The objective of this study was to survey SOM concentrations in CB greens throughout the continental U.S. to determine management practices, and/or their interactions, that significantly affect green OM content. Regression techniques were used to determine the significance of various management practices and site-specific characteristics on green OM content. Three hundred and eight putting greens on 104 golf courses in 15 states (AR-4, CA-3, CO-4, CO-8, IL-6, IA-6, MN-4, MT-9, NE-13, NJ-3, NM-6, SD-22, WA-5, WI-3, WY-8) were surveyed for management practices and SOM concentration from June 2006 thru June 2008. All golf greens surveyed were CB with varied levels of annual bluegrass (Poa annua L.). Three 0.75-inch diameter samples were collected per putting green to determine SOM concentration (three putting greens per golf course). Verdure was removed from the sample and discarded. Samples were cut to 3.0 inches below the verdure and the excess soil discarded. Samples were analyzed for SOM concentration (gravimetric concentration) using the loss-on-ignition method (Nelson and Sommers, 1996) at 750°F ± 5°F for 12 h. Survey data included: green age, annual precipitation, latitude, longitude, altitude, mean annual relative humidity, topdressing rate, material and frequency, course category (private vs. public), green construction method, CB cultivar, annual bluegrass (%, visual), mowing height, cultivation type and frequency, verticutting frequency, total nitrogen applied (yr -1 ), and plant growth regulator use. Golf courses that did not return surveys were eliminated from the regression analysis. Data analysis was performed using SAS version 9.2 (SAS Institute, 2008). Models were fitted by first examining bivariate