Ashton Franks, an M.S. student at Oklahoma State University, evaluated a 777 creeping bentgrass research putting green for the effects of nitrogen (N) rate and a mixture of three plant growth regulators (PGRs) on playability, turfgrass quality and dollar spot severity.
Nitrogen application treatments included 0, 0.1, 0.2, 0.3 and 0.4 lbs. N/1000 ft. sq. (0, 4.9, 9.8, 14.7 and 19.5 kg N/ha–1) per application arranged in factorial with three rates (0.28, 0.41 and 0.5 oz./1000 ft. sq. or 0.9, 1.3, 1.6 L/ha–1 per application) of a mixture of trinexapac-ethyl (1.4 percent), paclobutrazol (5.6 percent), and flurprimidol (5.6 percent). Applications were made every 14 days for 20 weeks, starting May 1 in 2021 and 2022.
Franks measured ball roll distance (BRD) using a Stimpmeter seven and 14 days after each N and PGR application. Visual turfgrass quality (TQ) ratings and normalized difference vegetation index (NDVI) were measured weekly to quantify aesthetic quality. He visually assessed dollar spot disease severity.
For TQ and NDVI, the N-treated plots had higher ratings than the 0 N treatment. Plots receiving PGR had significantly lower NDVI than the non-regulated plots. In both years, the 0 and 0.1 lbs. N/1000 ft. sq. (0 and 4.9 kg N/ha–1) plots resulted in greater BRD than the other three N rates.
The use of PGRs did not influence BRD in 2021, but the highest rate increased BRD in 2022. In 2021, the high N rate (0.4 lbs N/1000 ft. sq. or 19.5 kg N/ha–1) reduced disease incidence, while in 2022, plots receiving N had reduced disease compared to the non-fertilized treatment.
The high N rate decreased the average dollar spot size and diameter. Plots treated with PGR had less dollar spot disease than the non-regulated plots. Increasing N resulted in lower BRD but improved turfgrass quality. Both increasing N rates and using PGRs decreased dollar spot severity and increased turfgrass quality.
<p>The post Mike Kenna, Ph.D., recaps a study evaluating how nitrogen and PGR combinations effect bentgrass first appeared on Golfdom.</p>
