This post is for those who have asked sincere questions about dethatching and aeration. Hope it is of help to you. This is what I have learned from 21 yrs in the business, and applies to cool season turf. May also apply somewhat to warm season grasses. If you want confirmation or contradiction of my ideas, suggest you print this out and have it criticized by your state extension turfgrass office.<p>Dethatching and aeration are two big moneymakers in the turf maintenance industry. If your object is to make money, "dethatch" and "aerate" 'til your heart's content. If you want to do what is proper for the health of the turf, you need to understand some things.
The topic of "dethatching" was discussed in <a href="http://http://www.lawnsite.com/showthread.php?postid=16992">THIS THREAD</a>, and my last post there has links to university recommendations. Dethatching is done by a sod cutter or a vertical mower, and is very destructive to the turf. To call a machine with vertical flails or springs to scour the surface a "dethatcher" is a misnomer. These machines are just rakes, that loosen surface debris. The THATCH LAYER is a tightly packed mass of dead stems and roots, of the consistency of a thick woolen blanket, just below the surface, on top of the soil; no spring or flail machine is going to penetrate the thatch layer. For clarity, I will call the spring and flail machines powerrakes. I gave 4 uses for powerraking in the above thread, and I will also generally powerrake after a spring core aeration, just to break up the cores quicker; but in this case I set the flails to run 1/2" to 1" above the surface, and will powerrake a few days after the coring so the cores are dry. There may be many other legitimate uses for powerraking, but to claim you are "dethatching" is false.
Look closely at the debris brought up by powerraking, There are dead brown or tan grass blades that would soon decay, live green blades torn off the plants, and perhaps leaves and twigs. There is no thatch! Powerraking can be damaging to stoloniferous grasses. Powerraking increases weed growth by exposing more of the surface of the ground to light.
Aeration is a means of loosening the soil so air and water can penetrate better. Core aeration is also a way to control thatch. Most university recommendations state to core up to 10% of the surface to a depth of 4". The only way you will achieve that is with a reciprocating cam type machine, as generally used on golf courses. Years ago I tried most of the machines available, cam type and drum type. "Drum" refers to the equipment that rolls along the surface, available as motorized or push or pull types. In my judgement, most cam types were underpowered for use on most ornamental turf; they did OK with 3/8" tines, but bogged down with 3/4" tines. Also, as a friend of mine found, using the cam type was high maintenance, always breaking tines on roots, stones, etc.
With drum type aerators you are only getting about 2-1/2" to 3" penetration with new tines, and in one pass you will only penetrate 2% to 2-1/2% of the surface. As someone stated in a previous aeration thread, this is practically useless, when the recommendation is 10%. But a second pass will be more benefit, and a third or fourth pass can be really beneficial. I use the Ryan Lawnaire IV because the machine pulls itself thru the soil; a towed unit would not fracture the soil as effectively. I have seen very heavy soils where the first pass only penetrates 1/2", but the machine fractures the soil well enough that the second pass penetrates fully.
Also of consideration in ornamental turf, utility contractors today do not do a very good job of installing to code. I have killed a significant number of invisible dog fences, CATV wires, and phone wires in my years of coring. I am glad that I do not have a machine that penetrates deeper, maybe getting me in the range of a lazy electric contractor.
Does a coring benefit a lawn? The honest answer is maybe yes, maybe no. Some soils are nearly perfect, and cannot be improved. (This is in our region, where soils are glacial till: one half a property can be sand, the other half clay. In nearby all clay areas, coring is sometimes done 3-4 times a year.) Of my coring accounts, frequency ranges from 3 years to twice a year, depending on the site. Only way to really tell is to core half of a lawn and see if there is any difference next year. If you core half the back yard, and next yr the difference really shows, you have definitely sold this client on coring. Only in heavy soils will I specify that coring is necessary, and even then I will leave a small area uncored the first time to make sure I'm correct.
Coring controls thatch by bringing up soil into the thatch layer. Organic matter is decayed by soil organisms, but they cannot move into the thatch layer. By coring you bring up soil, and the organisms, into the surface, to be washed down and trapped in the thatch layer. I once was hired by a recent widow, whose husband had fertilized monthly and watered every day. The lawn was beautiful until he died, then it was terrible. It had 1-3/4" of thatch. Had two others look at it and they said sodcutter was only way to correct problem. But an elderly widow wants the old things, not something new. So I cored this lawn twice a year, four passes each time. Also since I had almost 10% of thatch sitting on surface, I powerraked when dry to remove thatch sitting on surface, and let soil filter into remaining thatch. In four years the thatch was below 1/2", and she had her husband's lawn back. Sometimes regular aeration is necessary to control thatch buildup.<p>Production aeration is good for the operator's pocketbook, but often has no true benefit to the lawn. I have seen large LCOs aerating with tines so worn that they barely penetrate surface, and don't pull a core, but you can bet they'll still bill customer $75/hour. Also have seen irrigation co on site couple days after coring; we flag all heads before aerating or powerraking. To run a drum aerator over a lawn once is not achieving an aeration. So when I charge $71.50/hr for proper aeration, I am making 2-4 passes with a drum aerator. I am using a relatively small machine (LA IV= 19" wide). If you are doing a proper aeration with a wider, properly maintained machine, you may be able to charge more. Proper aeration, if needed, will show real results. I charge my clients for maintaining the appearance of their property to the best of my knowledge. For those who do production, there are lots of people wanting coring, because the neighbor got it.<p>----------<br>Jim<br>North central Indiana
[Edited by GroundKprs on 09-08-2000 at 03:43 AM]