Nitrogen and Aerification Influence on Putting Green Thatch and Soil

‘Tifdwarf’ bermudagrass, (Cynodon dactylon (L.) Pers. ✕ C. transvaalensis Davy.), forms excessive thatch under intensive golf course management. Retarding thatch buildup or increasing its decomposition need study. This experiment was conducted 1) to determine the effects of ammoniacal and nitrate-N on turf growth and thatch production, and 2) to study the thatch-soil environment as affected by fertilization aenfication, and liming. An established Tifdwarf putting green was aerified at three frequencies (twice yearly, monthly, and biweekly) and fertilized with biweekly or weekly N at 0.48 kg/l00 m² from ammonium sulfate or calcium nitrate. Lime was applied to neutralize acidity, and soil topdressing was evaluated. Thatch thickness and weight and N content of organic-matter fractions were measured over time. Subthatch soil cores were analyzed for pH, K, Ca, Mg, and P. Bermudagrass root weights were also determined. Thatch thickness was extremely variable; maximum depth was observed under biweekly fertilization with ammonium sulfate combined with semiyearly aerification. Weight of thatch size fractions, though more difficult to obtain, proved a good indicator of thatch accumulation. Weight measurements supported thickness measurements. Ammonium sulfate produced maximum thatch weight, while increasing aerification frequency decreased weight of organic fractions collected. Ammoniacal-N did, however, produce excellent quality turf and 50% greater root weight was measured under ammonium sulfate fertilization. Soil levels of Mg and P were unaffected by treatments. Ammonium sulfate significantly reduced soil pH, Ca, and K as compared to calcium nitrate. Surface liming was not effective in retarding acidulation. No changes in thatch weight or N content could be measured. Thatch accumulation was not adequately controlled by combinations of aerification, selective N sources, liming or soil topdressing. Measuring thatch proved difficult, as did correlating thatch with turfgrass quality and growth.