SportsTurf

www.stma.org May 2016 | SportsTurf 17 The four cutting height treatments ranged from 1.0-1.75 inches. Sand topdressing treatments included either three split applications to total 40 tons/acre or an untreated control. Nitrogen treatments ranged from 2-6 lb N/1,000 ft2 and were further split by application timing (Table 1). Each N application was made with ammonium sulfate at 1 lb N/1,000 ft2. We applied the plant growth regulator Primo Maxx at the label rate of 0.60 fl oz product/1,000 ft2 on 28-day intervals to the entire experimental area. Research at Penn State has shown Primo can precondition Kentucky bluegrass to improve divot resistance, and this practice has been adopted by many NFL field managers and sod farms. In late November, 14 months after seeding, we used a sod cutter to harvest the sod at 1.75-inch depth and measured divot resistance for each plot. Divots were produced by dropping a weighted pendulum fitted with the head of a golf club pitching wedge. Smaller divots indicated high divot resistance. NITROGEN EFFECTS Of all the treatments, nitrogen rate had the greatest effect on divot resistance. When we began the study, a typical production cycle would include fall seeding, with 4 lb N/1,000 ft2 applied during the subsequent spring and another pound applied before the November harvest. We designated this treatment 4-1. The 4-1 treatment generally resulted in the worst divot resistance of the six N treatments. The most effective nitrogen regimes delivered just 3 lb N/1,000 ft2 during the entire season (2-1 and 3-0 treatments); these were nearly 40% more divot resistant than the "standard" 4-1 treatment. The Pennswing divot resistance tester (left); examples of small divots (above) and large divots (below) produced by Pennswing, with 12-inch ruler for scale. A duplicate study was also conducted at Tuckahoe Turf Farms. Plots were established atop a sand-based rootzone to mimic the native soil found at Tuckahoe and other farms that produce turf for sand-based fields. A four-cultivar blend of Kentucky bluegrass was seeded in September 2012 and 2013 (30% P-105, 30% Everest, 30% Boutique, and 10% Bewitched). The turf was fertilized with 2 lb N/1000 ft2 to quickly develop ground cover. Treatments began the spring after seeding. We chose three treatments: cutting height, sand topdressing, and nitrogen rate/ timing. The treatments were applied over the second growing season to simulate a typical 14-month production cycle (Sept. seeding and Nov. harvest the following year). The experiment was duplicated over the 2012-2013 and 2013-2014 production cycles. N program Mar. Apr. May June July Aug. Sept. Total N label † application 2-0 x x 2 2-1* x x x 3 3-0* x x x 3 3-1 x x x x 4 4-0 x x x 4 4-1 x x x x 5 † Each N application was made at 1 lb N/1000 sq ft via ammonium sulfate. *Fertilizer treatments which produced most divot-resistant turf Table 1: Labels for the six nitrogen treatments, based on the number of N applications made during the spring and fall months.

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