What is core aeration?
Core aeration is the removal and replacement of small plugs soil and thatch from your lawn. This allows air, among other things, to travel easier through your soil.
Reduce Soil Compaction
This one is a given. By removing cores of soil from the ground, you have allowed more room for the top soil in your yard to spread out. It is still the same amount of soil, only looser. This by itself may not seem all that important, but it is for the reasons explained below. It is also easier on your joints.
Improve Water and Fertilizer Absorption
After aerating your yard, you should notice less water run off when irrigating your yard. Since the soil is less compact, it will now allow water, fertilizer, beneficial bacteria and air to move more freely.
Improve Overall Plant Health
The plants will be healthier since beneficial elements, such as water, fertilizer, etc., are more readily available for the roots to uptake. Additionally, since the soil is looser, the root system will be able to develop more easily thus making your plant more able to compete for water in times of drought from weeds.
Beneficial bacteria will be able to move more freely in the soil and decompose thatch buildup. Thatch is simply a buildup of dead plant material between the soil and grass. A thin layer of thatch, less than 1/2" is beneficial and should not be seen as an issue. Thatch does not hold water or nutrition that is easily attainable for grass, thus making your turf have to extend its roots further to reach the soil. This leads to the grass not being able to extend its roots deep into the soil where there will be more access to water during times of drought. Thatch is also a staging point for many yard damaging fungus and a breeding ground for insects. By reducing the thatch, you reduce the chance of both fungus and insect damage.
What type of aerator to use?
Hollow Tine Aerator
A hollow tine aerator is my only recommendation for aeration. The ideal aerator to use should have a 3/4" diameter tine, 4" deep with the spacing between tines 6" apart. If you are a DIY person, you can rent a motorized one for small areas or one to drag behind a tractor for larger areas. My experience with renting a motorized one was back pain for a week. The rentals rarely have an adjustable height and shake you like a jackhammer. Be sure you have some pain reliever and a hot bath ready.
This only leads to additional soil compaction. This will make the problem worse, so please do not do it.
When to aerate?
The best two times to aerate are just after the first mowing in spring and in fall before your grass goes dormant. Be sure to make three to four passes with the aerator in the spring and only one or two passes with it in the fall. Do not aerate when the grass is dormant since you will only make it a more inviting place for weeds. There are exceptions to this. If there is a high traffic area, feel free to aerate monthly in the growing season.
How to aerate?
First, move anything that can be broken out of the way. Anything that can't be moved, irrigation heads, landscape lighting, drain covers, etc., should be flagged so you don't accidentally break them. If you have an irrigation system, let it run through a lite cycle while you flag the head. The aerator will work better if the soil is a little wet. Next, use the aerator like you would mow your yard, basically. The difference is a mechanical aerator will drag you around, but it is designed to do so. There should also be two handles, one to engage the tines and one to lift the tines. Be sure to have them disengaged and lifted when going over concrete or tile or when generally moving the machine. Now just make your desired number of passes and your done. Your yard may look like a large herd of dogs went through it at the moment, but once the soil dries and it gets some water, it will go back to looking normal again.
What else should do you with aeration?
Top dressing your soil with sand or additional top soil is a great idea immediately following core aeration. The new topdressing will help fill in the holes and refresh your soil, improving pH and drainage.
If you are in an area when with highly alkaline soil like most of Baton Rouge, you will need to increase the acidity of your soil. Soil dwelling bacteria break down sulfur over time and lower pH, but they are not very quick. Applying sulfur based products after aeration gives more access to the bacteria causing a lower pH in less time.
Apply Barrier Products After
You should not apply any pre-emergent herbicides or long term insecticides to your yard until a few days after aerating. Usually these products create a thin barrier that prevents their target pest from affecting your yard. If you aerate your yard after you apply one of these, there will punch holes throughout your barrier and will have wasted your time and money putting them out in the first place.