Impacts of Cultural Practices on Soil Organic Matter Levels in USGA Specified Ultradwarf Bermudagrass Golf Greens.

Ultradwarf bermudagrasses [Cynodon dactylon (L.) Pers. x C. transvaalensis Burt Davy] are used on United States Golf Association (USGA) golf greens in Florida due to their ability to tolerate high temperatures and produce fast green speeds. Their aggressive growth characteristics can quickly produce levels of soil organic matter (SOM) that are considered detrimental. This field experiment was conducted to determine whether cultural practices are effective at diluting SOM levels in a mature golf green that was constructed with a 90:10 (sand:sphagnum peat moss, v/v) USGA-specified soil mix. Three ultradwarf varieties — ‘FloraDwarf’, ‘TifEagle’, and ‘Champion’ — were subjected to: one, two, or three-time hollow tine aerification (HTA), three-time deep verticutting, five-time solid tine aerification (STA), and a topdressed control. Cultural practice treatments (CP) were applied in Spring-Summer (SS) and Summer-Fall (SF) studies due to year-long growing conditions. Soil organic matter was determined from 9.5 cm deep cores (with thatch and verdure removed), and the darkest stained layer. Turfgrass quality was not negatively affected by SOM, even though levels were as high as 6.5% (weight). Levels of SOM were highest in spring and winter, and lowest in summer. The darkest stained layer had 15% higher SOM. Root weights were 167% higher in winter than summer. It is best to apply CP before the fall, as recovery was fastest in SS. Although our CP equaled and exceeded USGA recommendations, no significant dilution of SOM was observed.