Author Topic: Introduction to Overseeding  (Read 1906 times)

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Introduction to Overseeding
« on: April 25, 2011, 02:33:00 PM »

Frequent overseeding is usually not necessary for lawns; however, overseeding several times a year is important for an athletic field.  Given the heavy use that generally goes with an athletic field, damaged plants do not have time to recover before being subjected to additional wear and tear. Therefore, you should overseed on a regular basis to thicken the turf and replace damaged plants with new ones. A quote from Paul Sachs in his book Managing Healthy Sports Fields puts this cultural practice into an understandable perspective: “Overseeding is a regular part of an aggressive, natural, organic program. The infusion of new seed into existing turf is, in essence, an injection of youth into a natural aging process.”

Overseed three times during the growing season: mid-April, late spring to mid-summer and late summer to early fall. If the field is a sod field, it is primarily bluegrass and should be overseeded with a bluegrass blend. On fields that are a mixture of seeded grasses, use a park mix that is a blend of perennial ryes and bluegrass.

Another factor that governs selection of a seed mix is the time of year and relative temperature of the soil. Seed germination of cool-season turfgrass is governed primarily by soil temperature. We need soil temperatures to reach 50 to 55 degrees Fahrenheit for germination, which occurs in our region in early to mid-spring, but can vary depending on the micro-climate in your area (near the coast, north facing slope, etc.). At that temperature, bluegrass takes roughly twenty days to germinate and some varieties of perennial rye take just eight to nine days. It therefore makes sense to use perennial ryes early and late in the season and a blend heavy to bluegrass during the warmer times of the year. Given that bluegrass blends are the most expensive seed mixes and can cost twice as much as a perennial rye blend that contains 20 percent bluegrass, you also save money by using a perennial rye-dominated blend during the colder months.

One of the benefits of having established a good soil profile is that an overseeding program will be more successful. If we have an inferior profile (low organic matter, high concentration of gravel), like that found on one of our new, poorly constructed school fields, then it becomes a very difficult task to try to get quality seed to germinate and get established. It is simply a matter of creating a quality seedbed to receive the seed.

In the fall, overseed with improved varieties of grass seed at a rate of 6 to 10 pounds per 1,000 square feet and fertilize with an organic fertilizer at a rate of 20 pounds per 1,000 square feet.

On golf courses or athletic fields, it is helpful to apply compost tea and fungal spores called Vesicular-Arbuscular-Mycorrhiza (VAM) to the seed, until you know that an active soil biology has been established. VAM is a naturally occurring fungus that helps plants take up phosphorus, nitrogen, and potassium in soil, in symbiotic exchange for carbohydrates provided by the plant. Biologically active soil naturally contains this fungus, but degraded (dry, eroded or chemically treated)may not.

If you are overseeding weedy areas or areas that were damaged in the winter (snow mold, etc.), use 75% ryegrass in the mix so that it will fill in quickly to out-compete the weeds.
« Last Edit: April 28, 2011, 05:32:18 PM by admin »