I get a lot of questions on GardenLine about replacing sections of a lawn ... or an entire lawn for that matter.
Here's a mnemonic device to help you remember the steps for a healthy solid-sod transplant: KILL, TILL, FILL & SOD. Following these steps is very important because of all the dead grass that needs to be replaced following the massive chinch bug damage we often incur in the summer.
When is the best time to replace grass? The simple answer is whenever you can find solid sod. We are fortunate in Southeast Texas to have scores of turf grass farms producing supplies year-round. So, you can just as easily re-sod in November or December as you can in any other month. I prefer replacing sod on cool days because it is hard work, and it is best not to transplant on days when the temperature is too cold.
The following process for KILL, TILL, FILL and SOD will work on St. Augustine, Bermuda and Zoysias.
KILL — The area that needs a transplant most likely has been overcome by weeds and unwanted wild Bermuda grass. So my advice is to first square off the area, marking it with rope or string or whatever you can find. Then spray it with a non-selective herbicide that will kill everything in the square. (Non-selective herbicides are products like Finale, Killzall, Eraser and Roundup. There will not be any residual in the soil from these herbicides.) Wait for the death and destruction to happen ... in most cases, the grass will be dead within a week. And this leads us to the next step ...
TILL — If you have a small area, use a steel-tined rake; if you are replacing an entire yard, you'll need a motorized tiller. In either case you will work the dead grass and weeds into and out of the soil ... plus you'll be beneficially loosening the soil at the same time. After tilling, it is normally an easy task to rake the dead grasses and weeds from the loosened soil. This leads us to the next step.
FILL — Even though you have loosened the soil somewhat, a re-sodding project will have a better chance of succeeding if there is a fresh layer of soil on which the roots can set up shop. Topsoil is good for this situation, as well as specially designed soils from soil yards. I am an advocate of a few in particular, especially those known as "Enriched Top Soil" (ETS), "Healthy Soil Compost," "Turf Mix," or "Turf Pro Mix." It should be a blend of soil, sand and compost that can be spread over existing soil - the soil you just tilled up. In any case, you should till or rake the new topsoil into the slightly loosened soil. Finally, make sure there are no low areas and that there is a "camber" (an ever-so-slight drainage curve), so rain will go to the sides and drain toward the street.
SOD — This is the back-breaking part, but it is the easiest in the sense that there is little to do but lay the sod where you want it. You must water it in and keep it well-watered for two to three weeks after transplanting. The continual water helps break down the muddy clay in which the grass was grown. Once it melts away, the roots will set up shop much quicker. It is not always necessary to fertilize immediately following a re-sod, but putting down granular iron a week after the consistent watering will help keep it green.
Good luck with your project.