SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: http://read.dmtmag.com/i/560546
www.stma.org September 2015 | SportsTurf 25 ful not to scalp the bermudagrass too low when you lower the mowing height. Scalping the grass will shock the plants. The seed can be dragged in with a metal drag or cocoa mat. This helps to work the seed down through the canopy to reach the soil. The last step is watering in the seed. Short frequent cycles of irrigation will help the seed to germinate more quickly. A more complex method to overseeding is to vertically mow, then horizontally mow lower, followed by spray- ing fields with a plant growth regulator, spreading the seed, topdressing, dragging in, applying a starter fertilizer, and watering. This method requires more time/effort and resources to accomplish. First vertically mow your field. For some bermudagrasses that are more aggressive, like Patriot, this may require going over the field twice or more in different directions. Vertically mowing will cut down through the thatch and thick grass canopy getting to the soil. The height setting on your vertical mower will depend on how aggressive you want to be cut- ting into your field. In some cases where the field is prone to overuse, like soccer goal mouth areas, you may want to be less aggressive by setting the verticutter to a shallower depth. Being less aggressive will help to protect these areas from wearing out from the high use. This is followed by mowing the grass a little lower than what you are currently mowing, which will allow the cool season grass to grow higher than the bermudagrass. After mowing the grass lower, spray the field using a plant growth regula- tor (PGR) at proper chemical label rates. Spraying the field with a PGR will assure that the warm-season grass will not flush back growth that will result in a dormant/ brown showing through the winter. In the Transition Zone, we receive some warm days in October that allow the bermudagrass to continue to grow. PGRs help to slow this growth down. The next step is seeding, which is followed by topdressing with sand. The sand helps to cover the seed and fill in the vertical mowing cuts. After topdressing with sand you can drag the sand in with a mat or brush. Dragging will help to work the sand down in the ber- mudagrass. Next you put out a starter fertilizer. This will be a fertilizer with a high percentage of phosphorus, such as 18-24-12 or a complete fertilizer such as 17-17-17. Phosphorus helps new plant growth. Some turf managers put this out soon after topdressing thinking that the fertilizer will be broken down and taken up by the plants as soon as the seed starts to ger- minate. Others wait to fertilize after the seed has germinated. Waiting until the seed has germinated makes certain that the new seedlings, not just the bermudagrass are able to take up the fertilizer. This process, just as before, is completed with watering. Short frequent cycles help to keep the soil moist to encourage the seed establishment process. Either one of the methods, simple or complex, will work well when it comes to overseeding bermudagrass with a cool- season grass. You can choose to use some of the processes or all of the processes when overseeding. For example if you are in the middle of a soccer season and there is not much time between practices/games on the field you may just put the seed out and have the players cleat the seed into the ground. Do not aerate or aeravate your field before overseeding. The seed will germinate in the aeration holes rather than having uniform coverage across the field. The goal is to get good seed to soil contact and plenty of water on the seed afterwards to successfully overseed a field. One guarantee for failure is never actually putting the seed out. SEED TYPES The most common type of cool-season grass seed used in the overseeding process is ryegrass, both annual and perennial. Ryegrass has the ability to germinate within 5-7 days. Annual ryegrass will germinate in 3-5 days, if conditions are right; it has a lime green color, which is lighter green than most other grasses. Perennial ryegrass will germinate in 5-7 days with correct conditions and has a darker green color, and is most often used for over- seeding fields. In recent years, some managers have been experi- menting with overseeding both annual ryegrass and perennial ryegrass on the same field. For example on a football field, alternating grasses every 5 yards to give a light green (annual ryegrass) versus dark green (perennial ryegrass) appearance on the fields. The drawback to this method is that using both types of grasses on one field makes managing more complex, because there are 3 different types of grasses on the field. RATES Many managers use different seeding rates depending on a number of variables including expected usage and budget. If high use of the field is expected and the budget is large, then a higher rate may be used. Normal rates for overseeding are between 8-10 lbs. per 1000 sq ft. For example, for a football field 57,600 sq ft would require between 460 lbs. and 576 lbs. of seed. To help offset usage and costs, rates can be higher Scott Strickland at the Durham Bulls. Overseeded perennial ryegrass and annual rye- grass on the same hill.