Features Agronomy
Options abound for overseeding of sports fields

When overseeding athletic fields, sports turf managers have a number of options as to the varieties and species from which to choose, with the objective being to achieve a safe playing surface.

Richard Goetz of Ontario Seed Company, speaking at the first annual Nutrite fall sports turf seminar in Milton, Ont., outlined the choices available to achieve the best possible playing field.

“The most important part is the dense turf aspect,” he said.

Because of the demands of user groups, some fields – especially soccer fields – are mowed as low as one inch or a half-inch and are prone to significant wear. Overseeding is therefore a “no brainer,” Goetz said. Soccer, football, baseball and cricket fields typically experience heavy wear during the playing season.

Overseeding of fields is traditionally done using perennial ryegrass because of its ability to germinate quickly and is often used with tall fescue. Kentucky bluegrass forms the “fundamental” sports turf surface because of its resilience and ability to self-repair.

“If you have irrigation and the budgets for the rest of it – fertilizer – it’s the choice, and you can keep it healthy.”

Even though the playing surface is predominantly Kentucky bluegrass, overseeding with the variety usually leads to failures, Goetz said. Overseeding with excessively high rates results in competitive inhibitions and mulching of the seed.

He said a popular mixture for overseeding is a blend of Kentucky bluegrass, perennial ryegrass and chewings fescue. Chewings fescue is tolerant of drought conditions and is therefore ideal for fields that aren’t irrigated. It is a good overseeding mixture for early fall applications to ensure good establishment in time for play to resume in the spring. Soil temperatures of about 18 degrees Celsius are ideal for seed germination.

Another benefit of chewings fescue is that it can handle compacted soil conditions and trampled areas and still perform well. But it forms in clumps, necessitating higher seeding rates.

Chewings is a variety from which cultivars are bred, Goetz said, adding J5 chewings fescue is a good choice when shade tolerance is needed.

Perennial ryegrass is quick to germinate, averaging about four days. Tall fescue and chewings fescue are in the middle of the spectrum while Kentucky bluegrass is at the opposite end.

“I really like tall fescue,” Goetz said. “It’s solved a lot of problems for some people who can’t get at intensive management. They have no irrigation or little of it and not as much fertilizing.”

Tall fescue is deeply rooted with some shade tolerance and is fairly disease resistant. It is, however, a bunch-forming grass, bunching up in stands that aren’t dense enough. It doesn’t heal well when torn up, thereby requiring stepped up overseeding.

Among the tall fescue varieties that have proven effective include Arid III, which has been successful in covering areas where pipelines have been installed; Inferno, which establish more rapidly than other varieties; and Summer, which has a leaf shape, colour and texture similar to Kentucky bluegrass but doesn’t form sod.

“If you were to overseed with Summer into Kentucky blue, that might be a good strategy if you want to start getting some of the tall fescue cultivars into your bluegrass.”

Other tall fescues can be somewhat bulky, Goetz said, but he noted Summer is “skinnier” than other tall fescues, resulting in mowing reductions of about 20 per cent.

Goetz said it is a good idea to blend Kentucky bluegrass in order to avoid a total monoculture. If disease or insects hit a monoculture of Kentucky bluegrass, serious problems can occur.

Excessive shade generally isn’t an issue with sports turf, but portions of a field can be in shade for extended periods at a time. Mature trees nearby can’t be cut which requires a bluegrass that is shade tolerant. A good choice of Kentucky bluegrass that works well in shade is Beyond, he said.

Jackpot is a good all-round Kentucky bluegrass that works well in most soil types, he added.

Perennial ryegrass, in spite of its ability to quickly establish itself, tends to lose its hardiness in more northern environments, but it still persists, Goetz said. Perennial ryegrass has worked well in overseeding playing fields in the Yukon Territory because there is ample sunlight there during the growing season and soils are sufficiently warm.

“You get a nice playing surface rather quickly with perennial rye.”

Goetz singled out such effective perennial ryegrass cultivars as Top Gun because of its ability to blend well with Kentucky bluegrass, and Revenge GLX which is a fine leaf rye and that is vigorous and attractive and takes only about three days to germinate when slit seeded.