How To Prepare Soil before Planting A Lawn
Have you always had trouble growing a healthy looking lawn? Have you religiously applied fertilizers, pre- and post-emergent weed killers, and fungus and insect control products, but still end up with unsightly bare spots and more weeds than lawn grass?

If you answered yes to these questions chances are it either has to do with the type of lawn grass you are trying to grow or, more often than not, there is a problem with the soil, or both. In some cases, drainage can be a problem. No lawn grasses can thrive in poorly drained soil that stays consistently soggy wet. Low-lying areas should be fixed so that they drain properly. In any event, a healthy lawn always begins with growing the right type of grass in the right type of healthy soil.

First, choose the right lawn grass!
Before laying all the blame on the soil for the ugly looking lawn that's filled with weeds and bare spots, the first thing I always consider is grass type. Planting and growing a variety of lawn grass that is known to perform well in a specific region or area is very important. For example, in my area of mid-Georgia, the lawn grasses that do best are the warm season grasses: Bermuda, Centipede, St. Augustine and Zoysia. No matter what you do, cool season grasses, such as fescue or bluegrass, struggle with the heat and humidity during our hot summers and require overseeding once or twice a year just to keep the grass thick and the weeds out. That being said, even the cool season grasses will perform better if the soil is healthy.

If low maintenance is what you're looking for, you want to choose the type of grass that grows best in your area and will meet the requirements of your yard. If you have a shady yard you want to choose a lawn grass that will tolerate shade. Same goes for a sunny yard. To find out what type of lawn grass will perform best in your yard consult with your local nursery and garden center or landscaping professional or your local extension service agent.

Okay, so you've found out what type of lawn grass will perform best in your lawn. Now it's time to check the soil health.

What is healthy soil?
Healthy soil is a must for thick, strong grass. Healthy soil for growing a lawn is one that is rich in organic matter, earthworms (Mother Natures tillers and natural fertilizer manufacturers), air, water and nutrients.

How to create healthy soil?
One of the most common problems homeowners and landscape contractors face has to do with soil density. If your soil is dense and compact, the first thing you want to do is loosen it up. The best way to do this is by adding some organic matter to the existing soil. Products such as mushroom compost, composted manures, river sand, or your own homemade organic compost will work to loosen the soil while also providing beneficial nutrients and organisms that are essential to plant health. A good native top-soil will also work well...provided it is rich in organic matter. Also consider applying gypsum, a soil softener.

You can add this organic matter by tilling or turning a layer of it in to the existing soil. How much organic matter you use will depend on the quality of the existing soil. For compacted soil, an average rate would be 1.5 to 2 inches or organic matter tilled to a depth of 4 to 6 inches or so. A 50/50 ratio would be even better. If you can not or do not want to till the soil, you can aerate with a core aerator and then top dress with organic matter or, preferably, a good native topsoil.

After tilling or topdressing, rake the soil to a smooth surface that will drain properly and then broadcast the grass seed or lay the sod grass. Remember, if you have low spots that will collect water take the necessary steps to fix these where they will drain properly. Also remember that few if any lawn grasses grow well under the canopies of large trees because the trees root systems are simply too much competition for soil space, moisture, and nutrients.

Okay, so you've taken the necessary steps to create healthy soil. Now, how do I maintain it?

Maintaining healthy soil
There are steps you can take to maintain healthy soil but, sometimes, maintaining healthy soil has to do with what you don't do to your soil.

You may have noticed that earthworms were mentioned above as one of the things that are present in healthy soil, and this is true. Earthworms are not as abundant or simply do not exist in poor, unhealthy soils, or soils that have been treated with certain fungicides and pesticides. Studies show that even one application of a fungicide or insecticide at the recommended rate will reduce the earthworm population in the soil. In fact, many common insecticides and fungicides sold over the counter can kill 60 to 90 per cent of earthworms present. In addition, other beneficial insects and microorganisms also are adversely affected by pesticides.

Research examining sustained turf pesticide use over time shows increases in the number of pests because beneficial predators and competing microorganisms are killed. Pest resistance to the chemicals also has developed. While these pesticides can be useful in severe disease or insect outbreaks, they are best used as needed and as spot applications rather than being routinely broadcast over the lawn on a routine basis.

So, you want to make sure earthworms are present and thriving in the soil. Just by adding fresh organic matter to the soil you have created an environment that earthworms will be attracted to and thrive in. If there are no earthworms present you can actually purchase them from local worm farms or from online sources. 
You'll want to introduce earthworms to the soil while it is freshly tilled.

In addition to the damage caused to soil by pesticides, a lawn care program calling for high rates of quick-release or synthetic nitrogen fertilizer will, over time, produce an excessive accumulation of thatch in the turf. The cause of thatch buildup is an imbalance between the production and breakdown of grass roots and stems at the soil surface. In lawns with more than three-quarters inch of thatch, water penetrates slowly, root growth is shallow and grass is more vulnerable to stress from heat and drought, and dethatching is necessary.

You also want to aerate the lawn at least one time per year with a "core" aerator that removes good size plugs from the ground. After aerating you can apply an organic fertilizer or a light layer of organic matter to refurbish the soil.

Maintaining healthy lawn grass
If the soil is healthy the lawn grass should be healthy and weeds and grass die-out should be minimal. That being said, there are a few things you can do to help your lawn grasses health through attention to mowing, watering, fertilizing and core aerating.

Mowing means mowing regularly and mowing "high" - 2.5 to 3.5 inches for most types of warm season grasses and 3.5 to 4 inches for cool season grasses, especially during the summer.

Allow the clippings to remain on the lawn; they naturally recycle fertilizer nutrients.

Regular and proper amounts of water maintain healthy grass and other soil life. Be careful not to overwater. No lawn grasses like a soggy soil. To avoid the onset of disease and fungus in the lawn, water during the morning hours and never in the late evening or at night.

Moderate fertilizing with a slow-release fertilizer provides nutrients to thicken turf and crowd out weeds.

And, as mentioned above, core aeration relieves and prevents compacted soil and allows grass roots access to air for healthy growth.