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danielj_2009

Can Aeration Actually Cause Soil Compaction?

11 years ago

Ohio State seems to think so! I found a great, semi-layman's article on the biology of soil compaction, here:

http://ohioline.osu.edu/sag-fact/pdf/0010.pdf

One thing I like about this article is it seems to be well sourced with lots of references.

What this article makes clear is that the "root" cause of compacted soil is poor soil biology. In a nutshell, the article explains that healthy soil has larger soil particles. These larger particles are created and "glued" together by glomalin. Glomalin only exists when roots interact with fungus in the soil. The fungus is a rather large structure in the soil (dchall likens it to the fungus you see if you leave bread out to spoil) so when you start disturbing the soil by tilling it, you destroy the fungus. This leads to destruction of glomalin production. In addition, the oxygen introduced by tilling overwhelms the natural biology. This excess oxygen consumes the carbon stored in the soil and emits it as carbon dioxide. The next effect is to reduce organic content in the soil, and allow a further reduction in particle size.

In the case of home lawn aeration, we're talking about pulling core plugs, not tilling the soil. However, it seems to me this kind of aeration can mimic the tilling problems reported in the study (breaking down fungus, introducing oxygen).

I'm sure this study is old hat for some of you, but I found it very informative. Lawntractor -- I'd be very interested to hear your take on this article. What are they missing? You've clearly given a lot of thought and study to the issue.

It seems to me that aeration might be useful in an emergency situation, like of the soil is oxygen starved or something, but routine aeration points to a biological deficiency that needs to be remedied. If so, why would I ever recommend that someone buy aeration equipment when the solution is biological?

All in all very interesting. I might even try to look up some of the references and see if they are available.

Comments (32)

  • 11 years ago

    No, unless you are using tines instead of pulling plugs. There is a reason greens and fairways are softer than the rough.

  • 11 years ago

    I don't know about the rest of the country, but in the southwest where i live, many of the soils are dense, compact, and alkaline. The only way to deal with it- is by physically altering the soil. Tilling and aeration are a must, or else struggle for years with shallow stunted root structure. I have seen many failed sod jobs, where the sod was laid on hard compact soil........soil so hard - a full sized vehicle can drive across it after a good rain, and barely make a dent. Wetting agents do nothing for soil like this......i know, i have tried on many occasions. On the other hand, some people over-do aeration to the max! I am thinking of the ex- head groundskeeper at Petco park in San Diego. He would aerate every chance he got , and the soil at that stadium is 100% sand ! Go figure, some people have completely "gone off the deep end" with aeration.

  • 11 years ago

    I've obviously never tried one, but the "recycling topdresser" is the most sensible aeration device I've seen. Take the dirt from below, spread & smooth over the existing turf while introducing the top inch or so to fresh air. Core aeration is definitely old technology. Now dryject says they have aeration machines that can inject thousands of pounds of sand into a soil profile in one pass without leaving any open holes.

  • 11 years ago

    Julian, Tom and Jake: For the moment let's ban any discussion of golf courses or other sports playing fields. Golf courses are mostly sand and are not representative of home soil properties. Football fields get a pounding by players and I suppose this is enough action to cause some compaction that might be relieved by aeration. However, not all aeration has the purpose of decreasing compaction (poking through an organic layer is one other reason). For whatever reason, people who maintain these fields want low organic content and I'm sure other variables that are at odds with a healthy home lawn.

    If we assume the article I posted is true, Tom, how can we conclude that aeration is of any long term benefit to solving the problem? If soils in the south west are "dense, compact, and alkaline" then why are they that way? If the magnesium content is too high and the soil is compact and alkaline as a result, then the solution is a chemical alteration. If the soil is dense and compact then maybe the organic content is too low and so the solution is to introduce more organics. Simply aerating or tilling up the soil is only going to result in the same soil profile after the soil settles back to it's natural state after enough rain and time. It's like if you have an oil leak in the valve cover on your vehicle. You could keep adding a quart of oil each week, but the real solution is to replace the gasket. If a soil is chemically and physically poor, then I don't see how mixing the poor soil up is going to change anything. It has to be changed chemically and biologically. I think that is one of the main points to get out of this article.

    Where am I going wrong?

  • 11 years ago

    >>If soils in the south west are "dense, compact, and alkaline" then why are they that way?

    It depends on the locale. In more arid regions, the sodium levels tend to be high as the rainfall levels are never sufficient to flush it out of the soil. High levels of excess sodium will create a completely deflocculated soil that's a complete mess.

    The longer-term fix there is to apply gypsum, which dispels the sodium, replaces it with calcium, and re-bonds the sodium into sodium sulfate. That can be flushed from the top soil into deeper layers, and you won't see it again in your lifetime. Na levels will still begin to rise immediately, however, as the low rainfall still brings in dissolved sodium, which deposits and doesn't get flushed out as the rainfall doesn't penetrate.

    Sometimes magnesium levels are out of whack, but that's going to depend on your area. The fix on that one is to balance calcium levels higher, if possible, and flush a bit of the magnesium...again, if possible. This isn't as easy a fix as high sodium levels, but it can be done. Gypsum may help a tiny bit, and using highly acidic fertilizers to readjust soils (monoammonium phosphate for P rebalancing, sulfate of ammonia for nitrogen feeding, and so on) will help drive out Ca and Mg. You then add the calcium back in.

    >>Where am I going wrong?

    You aren't. Nobody's saying that aeration doesn't provide a temporary benefit (temporary being defined, in this case, as less than a full calendar year) before settling right back into the original configuration.

    But for more permanent (on the order of years to decades) changes, there's absolutely no substitute for fixing soil biology and chemistry and letting them do the work for you.

    From Reeljake:

    >>I've obviously never tried one, but the "recycling topdresser" is the most sensible aeration device I've seen. Take the dirt from below, spread & smooth over the existing turf while introducing the top inch or so to fresh air.

    Darwin (yes, that one) did the most amazing studies on earthworms, which do exactly this over time, churning the entire soil profile every few years. The more worms, the faster it goes.

    >>Core aeration is definitely old technology. Now dryject says they have aeration machines that can inject thousands of pounds of sand into a soil profile in one pass without leaving any open holes.

    This would, however, be kind of unwise in the typical home lawn. The base soil usually isn't sand, and we don't want to add sand as it has a very low exchange capacity and water capacity. Not having reviewed the technology, I can't say if they remove plug-like things and then fill those up, or simply force in sand. If the latter, that could be a problem.

  • 11 years ago

    Tom it would be very interesting to see your soil test.

  • 11 years ago

    Big machines are just really dang cool & I have nowhere else to indulge my agrarian compulsions, so occasionally I have to move some soil. The wife thinks it's ridiculous too, don't worry!

  • 11 years ago

    morpheus: interesting stuff, and sensible as usual. The machine Jake talks about isn't subtle. Here's how it works, in a nutshell: http://www.dryject.com/howitworks/

    Jake: I hear ya'! I think I hear Tim Allen woofing somewhere.

  • 11 years ago

    OK, so now here's where things in this thread could get complicated. Based on the article above, and the discussion so far, I don't see any situation (non-sports field related) in which aeration makes any sense. It sounds like aeration is capable of providing a temporary boost for lawns growing in poor soil. So, we can say aeration is good if you want a one time boost for your summer picnic in three weeks, but those positive benefits will wear off relatively quickly.

    dchall has a favorite quip that the only thing aeration is good for is making someone's boat payments. This has angered a couple of people in the forum and I'm hoping to get real feedback from people like yardtractor and others who may believe that aeration has greater benefits than what we are attributing to it in this thread. The Ohio State report I posted above is well sourced and seems to make sense. I'm still looking for a non sports field related article that shows real benefits from aeration beyond a one-time boost.

    The other thing I'm looking for better information on is the idea that aeration plugs can contribute to additional weeds (a subject near and dear to yardtractor). Morpheus did produce one person who showed weeds growing out of his plugs, but that link seems to have changed. I wanted to do my own little plug/weed experiment, but I may be missing the window of opportunity to do that experiment this year. If I find more conclusive information on plugs and weeds I'll post it here. I certainly don't want to spread rumor or theory if it doesn't pan out in reality. If seeds below the surface really are present and dormant in aeration plugs, then I'd like to know why they don't germinate on the soil surface.

    Until I can find information to the contrary, I'm of the opinion that aeration is an attempt to solve chemical and physical soil problems through mechanical means (that is, stir up the soil). In addition, the idea that aeration plugs causes weeds is a theory in my mind until I can find a reasonable amount of evidence that it really happens.

    Thanks for any input in helping me sort this out for myself. I know I may be reinventing the wheel...

  • 11 years ago

    Hey, I aerated once (manually, using a Hound Dog aerator, which turned out to be rather more effort than I had initially imagined).

    The issue was, I was having the back patio and gardens put in, so the landscaper was driving his truck and other equipment back and forth along the same path, day after day, for several weeks. Frequently while hauling stone, soil, or stuff.

    He was very, very good about keeping to the same path as well as he could, so there were two severely compressed pathways with a standard distribution of compression around them from times he was a little off path.

    Nothing grew there and the grass didn't want to infiltrate again. The manual aeration, done rather heavier than average, did the trick and re-loosened the soil. The remainder of the job, below 3" and the physical break-up of the soil structure, I left to the worms and other biology.

    That's one case where aeration is a very good idea--heavy mechanical compression from machinery. You can do it in other ways, but the aeration jump-starts the process.

    Emergency rescue of a waterlogged soil wouldn't be outside the bounds here, either, but it doesn't get you around the problem of the waterlogging in the first place. For a rare or one-time flood event, aeration might be useful. For continuing or recurrent events, solving the issue is more important.

    >>I wanted to do my own little plug/weed experiment, but I may be missing the window of opportunity to do that experiment this year.

    I still have our discussed experiment in mind if I can fit it in. It turns out I'm rather more involved in stuff than I thought I would be, but still might have time for a limited trial.

    >>If seeds below the surface really are present and dormant in aeration plugs, then I'd like to know why they don't germinate on the soil surface.

    Often, the other way around. Weeds at the surface are covered by a light layer of soil, shadowing them from the sun. For weeds that sprout in darkness, this is necessary (just as I have to slightly bury vinca seeds when planting those as they won't sprout in any light).

    Topdressing will also tend to encourage some seeds as it holds more water and encourages sprout. So now you drop the plug up top where it can spread out, retain water on the seed, and encourage sprout.

    Scarification also comes into play, where the seed won't sprout until mechanically, chemically, or thermally stressed. The latter two are often done by other means, but the first one is definitely going to be exacerbated by aeration and friction with soil particles as they settle. Tree seeds tend to be on this list, and almost any seed with a coat benefits from gentle scarification by sand or silt particles. At home, I use a fine emery board or sandpaper of various grit sizes wrapped around a dowel.

    I've never done a study on soil seed bank numbers below the surface, but even that isn't impossible. Worm holes, previous aeration holes, and so on will tend to collect stuff. Dig it back up and there you go. Viability time on seeds does vary, anywhere from six months to several years under normal circumstances (up to thousands of years in special circumstances and given some types of seed).

  • 11 years ago

    A lawn grown on good top soil with good earthworm activity - never needs to be aerated .........however, often times lawns are started on soils which are compacted to the point where roots cannot penetrate more than an inch or two. These soils need to be opened up and amended with organic top dressing, or some other means of soil improvement ( such as the addition of sand or 'Turface') .

  • 11 years ago

    Tom: So I take it your position is that aeration can get grass started in poor soil as long as you follow up quickly with amending the soil so that aeration is no longer necessary?


  • 11 years ago

    Turface is meant to hold the holes open to encourage air & water flow, so if you go to the considerable expense of filling aeration holes with turface ($$$$) you will have changed the soil on a semi permanent level. On a lightly trafficked yard, I would say the soil profile change is permanent since you're not driving carts or playing rugby on it.

  • 11 years ago

    Yes Daniel, There will come a point where liquid types of aeration will be enough, as long as there isan't a situation where compaction is a continual problem due to heavy foot or vehicle traffic........and also when aeration is not used for thatch control. Some turf managers use aeration as a means of diluting thatch, but that method also involves sand topdressing.

  • 11 years ago

    Yep reeljake, Turface can give a permanent solution to water and air infiltration problems. The aggregate is very hard, and will last 20 years or so, (i think). Filling aeration holes with Turface , gives thousands of entry points for water to flow freely into the soil profile. I am surprised this product has not been marketed to the public more. Like you said, cost probably has something to do with it.

  • 11 years ago

    Damn. Prolly has a hemi, to boot!

  • 11 years ago

    >> Tom said: Yes Daniel, There will come a point where liquid types of aeration will be enough

    But why even use liquid aeration? I'm trying to explore the idea that NO aeration is required, liquid or mechanical, because the ecosystem you've helped establish with organic feedings and correct soil chemistry (population with worms, etc.) will do the trick.

  • 11 years ago

    Using shampoo as a wetting agent simply isn't the same thing as mechanical aeration. I could agree that after many years of babysitting your worms, fungi & bacteria it may render both treatments unnecessary, but to decree that they're interchangeable as part of your premise is just flawed logic. The most aerated lawn on earth may still need some shampoo to get rid of dry spots. A lawn with no dry spots may still benefit from aeration after the fence builders drive their trucks on it for a week. Neither will do both.

  • 11 years ago

    Daniel- I am going on the premise, that many lawns were started on less than ideal soil (happens more often than not where i live) , and so soil improvement therefore has to be done post establishment. The soil in the west is often dense, low in organic matter , and is watered with alkaline water from the Colorado river. Its all a prescription for a lawn grown on concrete :-)

  • 11 years ago

    If the shampoo were simply functioning as a wetting agent, I'd agree with you in part, but it isn't, and neither fungi nor bacteria require "many years" to grow. Weeks, tops, in good conditions Months to a single year at a droughty worst. Changes from shampoo are visible quite quickly to not at all, with the not at all being generally true on a severely chemically imbalanced soil.

    Of course, the only thing that works on a severely chemically imbalanced soil is rebalancing the soil.

    For mechanically compressed soils, aeration certainly jump-starts the process but isn't absolutely required. In a healthy, well-balanced soil, nothing's really required, it'll correct itself over time--but possibly more time than one wants to wait, so I'd aerate it.

    Dry spot is a completely different condition caused quite differently, so I'm not sure what it has to do with aeration. It's like saying that you may aerate, but you still need to feed the lawn. The fact that surfactants help with both dry spot and compaction is a peculiarity of the chemistry, just as some medications are effective on two or more extremely different diseases or conditions or both.

  • 11 years ago

    reeljake: I'm not sure if you are referring to something I said when you talk about using shampoo and aeration interchangeably. I never said that. In fact, I've used shampoo and couldn't really tell if it did anything or not. Not everything produces an immediate, discernible result but I trust people like morpheus who can attest to its benefits. Most times guys like morpheus can produce supporting data or evidence for the claims he makes. So if you make casual claims like it takes many years to build bacteria, worm and fungus levels, you're going to get called out to back it up.

    Tom: I completely understand where you are coming from and why you make a case for aeration. I started this thread because awhile back a guy came in here and started a thread to find out whether he should buy the "XK-4 turboblaster" or the "ZR-1 Hemi 4 wheel drive" mechanical aerator, or if he should just rent one instead. He never considered that actually aerators are unnecessary if you can manage to get the soil in good shape (or so goes the theory). I'm not opposed to using aerators in specific situations like you mention but newbies should be made aware that aeration is not a necessity like water and sunlight.

    The other issue we haven't delved into (well, I haven't anyway) is the idea that aeration can cause a weed outbreak. A couple of guys in the forum are big proponents of this idea, and there is anecdotal evidence on the internet of people having weed problems after aerating. It has been a hot topic as one other poster is dead set against the idea that dormant seeds can sprout when the plugs are pulled up. I'm still searching for more evidence and morpheus is going to do his own plug study if he can find the time.

    Thanks for the continued interest...

  • 11 years ago

    Just for the record, I like baby shampoo & put it down a few times a year.

  • 11 years ago

    Jake - do you aerate first before you put down the shampoo? :) j/k

  • 11 years ago

    I do walk around with my little yellow step aerator from HD first. No cores or anything, just 4 solid tine holes to open the root zone. I walk it around for a few minutes prior to any broadcast treatment, whether it's soap or preM or fertilizer.

  • 11 years ago

    Jake: so I take it you don't buy into the idea that artificially introducing oxygen into a balanced soil might do more harm than good? Or, if you do buy into that idea, is it that you think it is too difficult to achieve such a balance and you'd prefer just to keep doing what you've been doing because it gives you a nice lawn?

  • 11 years ago

    I think I just prefer the positive feedback I get from manually introducing fresh oxygen into the root zone. I don't believe oxygen will cause harm, certainly not in the small volumes I can introduce with my stepper. What I like & what works on my yard may not work anywhere else, but I enjoy working it & it works for me.

  • 11 years ago

    Sorry--Yes I do it because it gives me a nice lawn.

  • 11 years ago

    Jake: I hope you don't think I'm pestering you. dchall and other say that their experience comes from finding out what others are doing that works for them, so I'm just trying to find out more about what you do. I'm going on the theory that if something like aeration improves your lawn then there may be something out of whack. On the other hand, maybe a little aeration has a beneficial effect on all lawns. Have you ever done a Logan Labs soil test or any soil test that you could post?

  • 11 years ago

    There is something wrong, I have Bermuda grass & it has a constant desire to grow & if I dont give it room to grow horizontally it will grow vertically. That makes for the same amount of work with a drastically better lawn. Anyway, beneficial for my yard, but probably not for all lawns. Your mileage may vary.

  • 11 years ago

    Jake - not sure I quite understand, but I guess Bermuda is a different animal. Still, it seems like a soil test would be interesting, if for no other reason than just to have the information... like getting an annual physical or a car inspection.

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