Originally Posted by JoJo1990
Axe - That is poor information.
Thatch layers can increase and build for a number of reasons. When thatch, especially in cool season lawns, reaches over a half of one inch thick, it should be reduced. This would be an excellent time to verticut or use a power seeder to first de-thatch and then collect that layer. Next, add the seed to your machine and do your seeding passes. You will still pull up more thatch on these subsequent passes but in most cases, that can be left on op of the grass and it will fall back down to the soil on its own.
I've seen little thatch reduction when core aeration is used for the sole purpose of reducing thatch, although it does help to some degree.
I'm with Smallaxe on this one. (although we disagree on aeration. I feel it should be done yearly for multiple reasons)
Per the Ohio State University Extension. (http://ohioline.osu.edu/hyg-fact/4000/4008.html
"Thatch control is both preventive and curative in nature. Thatch prevention can be managed by proper use of fertilizers and pesticides and the implementation of proper cultural practices. Maintaining a soil pH between 6.0-7.0 encourages microbial degradation and earthworm activity. Selecting turfgrass species which do not commonly form thatch will also prevent/reduce the rate of thatch development. Mowing grass regularly at proper heights (generally 2.0 to 2.5 inches) can also help slow thatch build-up. The turfgrass clippings only need to be removed when grass is wet or extra long and a layer of clippings remains on the surface.
Topdressing, the process in which a thin layer of soil (1/8 inch) is added onto the turf, is an another preventive approach which will help prevent thatch build-up. This light coating of soil helps improve the environment at the soil surface and facilitates microbial activity and thatch prevention. This soil should be similar in texture to the original soil to prevent drainage or other problems due to incompatible soils. Peat moss or other high organic materials should not be used, as these products will add to thatch deposition. Topdressing should not be added on top of an already existing thatch layer. A serious layering problem will result, further complicating turfgrass culture.
Curative control measures should be implemented once thatch accumulation has begun but before the layer exceeds 0.50 inch in thickness. Cultivation practices that address existing thatch layers include dethatchers (i.e. power rakes, lawn combers, vertical mowers), mower blade attachments and core aerification. For many years, dethatching was recommended as a way to remove the thatch layer. This method physically removes the thatch and is most effective if the existing layer is less than 0.50 inch in depth. This operation should be done during a cool season of the year when several weeks of good growth and recovery can be anticipated following the dethatching. Experience has shown that early fall is the best time for removing thatch. Fewer weed problems occur and two growing seasons (fall and spring) follow before the lawn encounters summer stress. Very early spring is the next best time. Machines for removing thatch can be rented at most tool and equipment rental companies. In recent years, various mower blade attachments have been advertised by retailers. These blades come equipped with steel prongs which physically tear the mat and thatch layer during the mowing operation. Even though a considerable volume of material is pulled to the surface, these attachments usually have little impact on the total quantity of plant debris in the thatch layer. Some damage to the desirable turfgrass should be anticipated with these attachments and, therefore, should only be used in the spring and/or fall during periods of favorable growing conditions.
The last option, which research has shown to be the best approach to thatch control, is core aerification.
Core aerification, also referred to as aerification, is the process where hollow tines are used to remove plugs of thatch and soil from the lawn and deposit them on the surface. Once the plugs of soil are deposited on the surface, rainfall or irrigation will incorporate the soil into the thatch layer. This soil addition to the thatch layer will improve the environment in this area resulting in increased microbial activity and thatch breakdown."