Seed-to-soil contact is essential when overseeding
Fall is a great time to renovate a poor performing turf site with cool-season grasses. Both seeding and sodding can be highly successful when done in the fall. It is important to ensure good seed to soil contact when seeding into an existing stand of turf. Seeds that get hung up in thatch or other foliage can dry out and not establish properly. Here’s a short description of how to seed into an existing lawn and maximized seed-to-soil contact.
First, assess the stand. If you are happy with the current grass species and variety, then an application of a non-selective herbicide may not be required. If there are many weeds and/or the existing lawn is an older variety, it would be best to kill the existing vegetation and start over with newer seed varieties. Two applications of a herbicide like glyphosate may be required to completely kill all the vegetation.
When you are ready to seed, buy or rent a drop seeder to ensure uniform coverage. Make sure you use the wheel guides to align your passes. Splitting the seed rate and walking in two directions helps ensure great coverage over the whole site.
To maximize seed-to-soil contact after seeding, use an aerator or power rake/dethatcher to press the seed into the soil. A mechanical slit seeder also increases seed to soil contact. Research at UNL showed all three methods were equally as effective, though the pattern of seedling emergence varied greatly. Grass species did not matter.
Apply some starter fertilizer (0.5-1.0 lbs P2 O5 per 1,000 sq ft) and then keep the seed wet. Watering two to three times a day is usually fine for most Nebraska soils. Sandy soils, however, may need a few extra irrigation events until the grass germinates. Start mowing when the turf achieves the desired mowing height (don’t wait too long) and provide one more application of starter fertilizer after that first mow. If the weather cooperates, you’ll have a good-looking turf stand by Memorial Day.
Bill Kreuser, Assistant Professor and Turfgrass Extension Specialist, firstname.lastname@example.org