Managing 'Mini-Verde' Bermudagrass Putting Green with Variable Topdressing and PGR.
Haibo Liu, Lambert McCarty, Williams Sarvis, and Christian Baldwin. 253 P&A Building, Clemson University, Department of Horticulture, Clemson, SC 29634-0319
The study had been carried on at Clemson University, Clemson, South Carolina from June 2006 to Sept. 2007. ‘Mini-Verde’ bermudagrass (Cynodon spp.) was established from washed sod in March 2005 on a USGA specification green with 85:15 mixture (v:v) of sand and peat-moss after a fumigation using methyl bromide. The research green has been mowed at 3.2 mm daily during growing season and each year received three core aerifications by 5 cm tine space using 1.3 cm diameter tines plus two vertical mowing with a depth of 1.3 cm from June to August. A combination of 50:50 granular (18-3-18) and liquid fertilizer (10-3-5 and 5-0-7) have been applied from March 2005 to October 2005 , from May 2006 to Sept. 2006 weekly, and from May 2007 to Sept. 2007 weekly at rate of 12.2 kg N /ha with a total annual input N of 439.2 kg N/ha, which was 150% as a recommended rate N for the cultivar in order to stimulate thatch accumulation. The study was designed as a split-split block design with four replications including 18 treatments. The main split blocks included three treatments of 18, 36, and 54 mm in depth of annual total of sand and peat-moss mixture topdressing materials (85:15, v:v) applied weekly. Weekly topdressing had been applied in 2005, 2006, and 2007 starting late June or early July and ending in October. The main blocks were further divided into two sub-blocks with or without groomer mowing treatments three times weekly from July to October in 2006 and 2007. The complete randomized block design treatments including three PGR treatments: without PGR, trinexapac-ethyl [Primo, a rate of 0.025 kg a.i./ha (1EC)], and a tank mix of TE and flurprimidol (Cutless 50WP), a rate of 0.0125 and 0.08 kg a.i./ha , respectively treated in July and August biweekly in 2005, 2006, and 2007. The data collection included monthly turf quality, monthly clipping yield and chlorophyll concentration, monthly root mass, and monthly thatch depth. The best turf quality were the treatments with Primo with the least clipping yields and highest chlorophyll concentrations under a moderate topdressing rate. The results also showed that light topdressing (18 mm) weekly slows thatch accumulation more efficiently than others. Groomer mowing also reduced thatch accumulation and heavier topdressings did necessarily reduce thatch.