OVER DO IT
With the months of April, May and early June behind us and the sultry months of summer creeping in fast, the best part of the turfgrass growing season also is behind us. The later months of summer usually are the roughest on turf and these months can wreak havoc. Whether you live in the North or South, the loss of turfgrass can affect home lawns, athletic fields and even golf courses. If you've ever experienced a wet, cool spring, you know this can have an effect on the early establishment of turf; then, if the weather turns extremely hot and dry during the late summer, this sets up the scenario for extensive grass loss due to the lack of moisture and extreme heat. Add to the mix high humidity and it immediately will put the plant under stress, very likely resulting in disease and wiping out turf. If you find that the turf you manage has suffered from disease, drought and insect damage, you might want to look at doing some renovation by overseeding areas that have been affected.
DEAD OR ALIVE?
Before you move ahead with a major or even a minor renovation project, it's important to figure out how much work you'll need to do to re-establish the area. If the grass never recovered from summer damage and is completely wiped out, you're looking at a major renovation project. If you see green turf and small areas of thin turf, you may see results by instituting a fertilization program. If conditions remain favorable, the small damaged areas will fill in and go into winter healthy. If damaged areas range up to 400 square feet, if only 50 percent of the lawn area is healthy or the turf density provides less than 70 percent coverage, you should consider overseeding to maintain a weed-free, uniform turfgrass surface.
TIMING IS EVERYTHING
Late summer or early fall is the best time to overseed lawns. This will be your call, because if you are in the East, North, Mid South or West, what constitutes late summer or early fall certainly can vary. Determine timing by watching the weather, not the calendar. Soil temperature and atmospheric temperatures have the greatest impact on seed germination and growth, and these are most favorable during this portion of the year. Adequate moisture, sunlight and fertilizer will help guarantee that the new seedlings will be well established before the cooler fall weather sets in. Also, seedlings will benefit from less weed competition at this time, giving them a better environment in which to develop and grow. The overseeded areas will require the addition of a starter fertilizer (1-2-1 ratio of nitrogen [N]-phosphorus [P]-potassium [K]), which is high in phosphorus to promote good establishment. You can apply one to two applications of starter fertilizer over a three- to eight-week period, supplying approximately ¾ to 1 pound of N per 1,000 square feet each time. Water frequently and lightly for the first two weeks after seeding is complete. You can gradually reduce the frequency and increase the duration of the irrigation to encourage a more vigorous root system. For more detailed information about this process, see “How To: Overseed,” page 44.
WHAT TYPES OF GRASS SEED
Your choice of seed is generally determined by your climate. Cool-season grasses such as Kentucky bluegrass, perennial ryegrass, bentgrass and fine fescues are used in the northern, eastern and western regions of the United States. These grasses will tolerate moderate summer temperatures and will survive severe cold associated with the northern winter conditions. If you are in the southern part of the United States, you may use centipedegrass or bermudagrass. These will tolerate the extreme heat in this section of the country.
THE RIGHT MACHINE TO COMPLETE THE JOB
There are a number of different methods to ensure that your reseeding efforts are going to be successful. First, you want to make sure the seed will be in contact with the soil. If you just broadcast the seed onto the soil and existing grass without creating some type of hole or slit, your seeding attempts will be just that: an attempt.
There are several options for creating holes or slits to promote good seed-to-soil contact. Machines that can give you the soil preparation necessary for good seed contact are core aerifiers, power rakes and slit seeders. The best machine for doing this type of renovation is the slit seeder. A slit seeder combines vertical mowing with seeding. And a slit seeder will also offer a much higher germination rate than broadcasting because the seeds are deposited into the soil via the open slit. As the machine is propelled across the lawn, it opens the soil and deposits the seed into the soil approximately ¼ inch deep. Most slit seeders are adjustable to go deeper because the ground you're working on may have ruts or contours, and if so, you may need to adjust the slit seeder to put the maximum amount of seed in contact with the soil. The slit seeder meters seed at a predetermined rate. Manufacturers of slit seeders recommend that you make two passes at a 45-degree angle at half of the recommended seeding rate. Most manufacturers attach the seeding rate to the seed hopper for your ease of calibration. You may want to then roll the area, closing the open slits to ensure better seed-to-soil contact.
MANUFACTURERS OF SLIT SEEDERS
Manufacturers such as BlueBird, Husqvarna, Jacobsen, Turfco and Toro produce slit seeders that can certainly fill your needs. BlueBird manufactures the model S22 slit seeder for the rental market and commercial users. It has a ground-driven agitator that distributes seed with a 22-inch swath. It has seven preset height adjustments in ¼-inch increments. The seed hopper fits on the rear of the unit and has a 30-pound capacity. The handle is padded and adjusts to three positions for use and a fourth position (folded) for transport. It is powered by a 5.5-hp Briggs & Stratton or Honda engine. An 8-hp Briggs operates the 22-inch power rake with their Delta reel and seeder box. The Delta blades are made of 12-gauge steel that is angled with a beveled edge to cut slits into the ground 1.25 inches apart. The seed hole size is adjustable to accommodate a broad range of grass seed varieties.
Another seeder in the market is the Husqvarna DT22BF/SB22. Electrolux owns and manufactures the sister brands of BlueBird and Husqvarna products. The Husqvarna slit seeder has many of the same features as the BlueBird, with only a couple of differences. The Husqvarna has a more ergonomic handle assembly in that it curves in at the corners and uses the bail to engage the belt system; however, this unit does not use a preset height adjustment like the Bluebird.
Turfco Direct offers the LS-20 unit that is popular with both landscape contractors and the rental market. It can seed more than 30,000 square feet per hour with a seeding swath of 20 inches. The cutting blades are 1.5 inches apart for close seeding and can be replaced without removing the cutting head, by just removing two bolts. The LS-20 uses a micro-screw depth adjuster that is adjustable to 1.5 inches above the ground to 1.5 inches below the ground. The seed box capacity is 30 pounds and uses a mechanical, cam-action adjustment to handle different sizes of seeds. The unit's standard engine is a 5.5-hp Honda. It is designed with a spring-loaded belt for the drive system and a fold-down handle for storage and transport.
Jacobsen manufactures an overseeder called the Ryan Mataway. An 11-hp Kohler engine powers the Mataway. The depth adjustment can reach any desired depth up to 1.5 inches with a seeding width of 19 inches. The hopper capacity is 0.83 cubic feet and features a rotor bar, which is made of neoprene rubber. The metering system uses stainless-steel plates with triangular holes to create a variable opening for all seed sizes. The rotor bar operation engages in the lowered position only and the seed gate automatically shuts off when the unit is raised. You can remove the rotor bar and metering device for easy servicing. The lower seed delivery system has 10 seed outlets with 2-inch spacings. The seeder drops the seed through these outlets alongside the discs, which are heat-treated with scrapers for keeping the mud off. You can remove these discs to use the unit as a dethatcher only. The reel features a fixed-blade arrangement with 10 eight-point heat-treated blades spaced on 2-inch centers.
If you are going to be doing very large areas of turf for your overseeding project, two larger slit seeders are available. One is manufactured by Jacobsen and is the Ryan 548 Aero-Blade and seeder. This unit is a standard three-point-hitch unit that you can use as a vertical mower or an overseeder. The 548 uses a PTO drive to turn a heavy-duty gearbox that has a 45-hp rating. The blades are 10 point, 12 inches in diameter and have a standard 3-inch spacing. The depth adjustment is from 0 to 3 inches. The 548 seeder offers a seeding width of 48 inches and a hopper that can hold up to 100 pounds of seed. The seed spacing gives you 3-inch seed rows. The discs are 12 inches in diameter, made of steel and use spring-loaded scrapers to keep the discs clean. The seed flow-rate gauge is adjustable with an optional speed-up kit to increase the seed-flow rate by up to 25 percent.
The Toro Co. also offers a tractor-mounted unit that is mounted with a three-point hitch. The unit is the Aerothatch 83 with 93 seeder. The 83 Aerothatch is 48 inches wide with variable depth settings. It uses a 65-hp-rated gearbox and 10-point blades on a high-carbon steel blade shaft. The seeder attachment is ground-driven with a seed capacity of 100 pounds. This unit will plant seeds in 16 parallel groves on 3-inch centers and allows you to calculate seed-flow rates for any seed and turf area.
Finally, don't be afraid to get out there and mow the newly seeded areas. Don't let the new seedlings get to 3 or 4 inches before you begin mowing. Start mowing them when they get to about 2 inches high. Mowing the turf helps it spread laterally and helps fill-in the area; so fire up that mower and begin cutting some grass. Hopefully, these tips and the equipment description will help you reclaim those thin and bare areas, and get you on the way to healthy turf for the upcoming growing season.
Tony Tredente is national sales manager for Locke Turf Inc. (Opp, Ala.).
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