Repairing clay lawn
My soil is heavily clay, but I have not had a soil analysis done yet. Our yard is approximately 7,500 sq ft, and our property is adjacent to orchard grass fields in Jefferson. We constantly fight random orchard grass clumps growing in our yard due to the proximity to the grass seed fields. Our grass has always struggled. Last spring I leveled low spots with Liam soil, aerated, thatched, fertilized, and reseeded/overseeded the yard. This spring 30% of the yard is dead/bare and over grown with weeds. I need help on improving our grass so we can enjoy a yard, not mud. Would it be best to cut the old sod out and start over or try to work with what we have?
Marion County Oregon
First of all, a soil test is always a good idea to determine if you have a nutrient issue causing problems. Second, watering is an important issue with clay soil. Be sure the soil is moist down 4" - 6" to have healthy root growth, but not saturated preventing gas exchange.
Now to your question - You will have to make that decision. Before you can truly fix your lawn you will need to find out what the problems are that cause your turf grass to continue having issues. Check watering practices - make sure constant moisture is getting to the roots. Why are you de-thatching - do you have a thatch layer greater the 1"? Greater than 2"? Is your soil compacted? When you aerate are you adding a layer of compost when you over seed. Are you using the proper type of grass when you over seed? Have you tried a preemergent herbicide to reduce the weedy grass from germinating in your lawn? Adding organic matter will help with water and nutrient holding capacity and aeration of the soil.
I'm assuming you irrigate your lawn. After watering use a shovel to open up the soil slightly and look at how far down the soil is moist. Adjust watering schedule to keep soil moist throughout the growing season. If you have a large thatch layer 2" +, it take a few years to remove it. De-thatching is tough on a lawn, so be sure to do it when the grass is actively growing and don't remove too much at one time. When aerating add organic matter in the form of a compost, along with overseeding. Overseed with the same type of grass you have in your existing lawn. You will need to fertilize your lawn after it is established to keep it thick and vigorously growing to choke out weeds. Don't mow too low. Depending on the type of grass 2 1/2 inches is appropriate. If you mow too low the grass plant roots don't grow well and are predisposed to summer drought and more weeds. Herbicides can help with broadleaf weeds and preemergence can help with the grass weeds, but grass weeds are difficult to manage and may need digging out or killing with a glyphosate herbicide.
If you do a compete renovation and remove your existing grass, this would be a good time to add the organic matter. Be cautious when bringing in new sod that it doesn't have a very thick layer of thatch.
Here are a few publication that may help you make a decision on patch renovation or complete renovation of your lawn. If you have more questions visit your local count Extension office. The Master Gardeners are always willing to help.
WSU publication Home Lawns
OSU publication Practical Lawn Establishment and Renovation
UC Davis publication Lawn Renovation http://www.ipm.ucdavis.edu/TOOLS/TURF/RENOVATE/