Common bermudagrass (Cynodon dactylon) is considered an aggressive and fast-spreading turfgrass grown from seed, while hybrid bermudagrass (Cynodon dactylon × Cynodon transvaalensisis) is a sterile, crossbred turfgrass established through sod, sprigs or plugs. Hybrid bermudagrass typically has a finer leaf texture and darker color compared to common bermudagrass, which has a coarse leaf texture and lighter color.
Common bermudagrass has been available by seed since the 1940s, but it produces poor turf quality. The desire for better-quality bermudagrasses led plant breeders to develop improved hybrid vegetative cultivars, because hybrid bermudagrasses typically produce better density and playability. With the help of genetics and plant breeding, seeded common bermudagrass cultivars have been developed that produce quality characteristics comparable to vegetative hybrid bermudagrass cultivars.
Information is needed on the optimal nitrogen (N) requirements for establishing seeded bermudagrasses. Therefore, researchers at Purdue University wanted to determine the optimum N grow-in or establishment program for a seeded bermudagrass cultivar.
A two-year field study was conducted on silt loam soil with a pH of 7.1 and 5.2% organic matter. Rio bermudagrass was planted at 1-pound pure live seed per 1,000 square feet (4.9 grams per square meter) in June 2020 and at an adjacent site in June 2021. The areas were covered with a seed germination blanket to minimize seed movement into adjacent plots, then removed 21 days after planting due to visible bermudagrass emergence. The study areas were irrigated to promote germination and emergence and mowed every five to seven days at 0.5-inch (1.27-centimeter) height-of-cut.
In both years, granular fertilizer treatments were imposed in a randomized and replicated manner typical with turfgrass field studies. The treatments consisted of a fast-release N source (ammonium sulfate; 21N-0P2O5-0K2O) and a slow-release N source (polymer-coated urea; 44N-0P2O5-0K2O). The treatments were applied at different intervals and amounts of N per 1,000 square feet (square meter): Ammonium sulfate was applied at 0.25 pound (1.2 grams) N every seven days for 1.5 pounds (7.3 grams) total N; 0.5 pound (2.4 grams) N every seven days for 3.0 pounds (14.7 grams) total N; 1 pound (4.9 grams) N every seven days for 6 pounds (29.3 grams) total N; 0.5 pound (2.4 grams) N every 14 days for 1.5 pounds (7.3 grams) total N; or 1 pound (4.9 grams) N every 14 days for 3 pounds (14.7 grams) total N; polymer-coated urea was applied at 1 pound (4.9 grams) N only at planting or 2 pounds (9.8 grams) N only at planting. An unfertilized treatment was also included.
In both years of the study, individual test plots were evaluated by digital analysis for percent green cover every five days. In the second year, clippings were collected, oven-dried and measured to assess dry matter production.
Combining information from both N treatments, the time to achieve 50% green cover ranged from 20 to 23 days in Year One (24 days for non-fertilized plots) and 23 to 27 days in Year Two (30 days for non-fertilized plots). Time to achieve 90% green cover ranged from 26 to 31 days in Year One (33 days for non-fertilized plots) and 32 to 40 days in Year Two (41 days for non-fertilized plots). Therefore, when establishing bermudagrass from seed in June, three to four weeks of emergence and growth are needed to achieve 50% green cover and four to five weeks for 90% green cover.
When bermudagrass is seeded in June and rapid establishment is needed, applying a total of 2 to 3 pounds N per 1,000 square feet (9.8 to 14.7 grams per square meter) from ammonium sulfate during the first 60 days-after-planting, or applying 2 pounds N per 1,000 square feet (9.8 grams per square meter) from polymer-coated urea at planting, is sufficient to maximize seed germination and emergence on a silt loam soil. Also, this amount of N did not produce excessive bermudagrass clippings during the establishment period.
The results from this study reinforce the importance of N fertilization during seedling establishment to promote growth, density and vigor. Possible reasons to establish bermudagrass from seed instead of vegetative methods include: flexibility in establishing scheduling, increased genetic diversity, improved winter hardiness and reduction in established costs.
Source: Powlen, J.A., and C.A. Bigelow. 2024. Seeded bermudagrass establishment as affected by nitrogen source, rate, and application frequency. Crop, Forage & Turfgrass Management 10 e20250.
Mike Fidanza, Ph.D., is a professor of plant and soil science in the Division of Science, Berks Campus, at Pennsylvania State University in Reading, Pa. He is a 24-year member of GCSAA.