I have used sand which, by itself, was not terribly helpful in dealing with clay. The clay just re-congealed around it. It did work well when combined with compost.

Let me just push back a bit on the use of organic materials. Don't write them off. Compost when completely decomposed is humus, which is a remarkably stable product in the soil. It will last for hundreds if not thousands of years. It also provides habitat for the organisms that will continue to break up the soil and make pathways for plant roots.

Just adding sand to clay soil will actually compact your soil even more. What you need is more organic matter. Compost would be my first choice to amend any clay soil.

If organic amendments are not lasting long, try adding those that have harder-to-break down components. Mostly this would mean woody materials with lots of lignin, the hardest component to decompose and generally big part of stable humus.

Add organic material to that soil, no sand, no gravel, nothing but organic matter. Organic material is not supposed to last long in soil because it is a food source for the Soil Food Web that works to keep soil in good condition.

Soil is supposed to be composed of the mineral component, the sand, silt, or clay part, of about 45 percent, organic matter of about 5 percent, air of about 25 percent, and water of about 25 percent. The organic matter helps keep the air and water in proper proportion.

kimmq is kimmsr

What is the use of this area "of importance"? What caused the compaction in the first place? Is it a heavy traffic area? Have you considered putting down something other than new lawn?

You might consider keeping some 'greener' stuff in your organic materials (i.e. not just woody materials - shredded leaves should work). Ideally you would see earthworms etc active, pulling edible materials down through the soil and doing the 'tilling' for you, and I think they'd benefit from a more varied diet. On an ongoing basis, 'superficial' topdressing will hopefully continue to feed them. Also, don't remove your lawn cuttings - mulch and leave them to feed and build the soil food web.

Keeping a turfed area "permanently" free of compaction is a bit of a pipe dream :-)) Turf areas naturally lean towards compacted soils over time simply due to foot traffic, pushing lawn care equipment over them and from rainfall and irrigation. It really has little to nothing to do with the soil quality initially. That's why mechanical aeration is so often suggested annually or when renovating a lawn.

I'd agree to the addition of organic matter before any sand or gravel and durable OM at that - bark or wood chips, not just compost. This will certainly alleviate the situation now but be prepared to engage in manual aeration (core or plug aerator) going forward to keep rectifying the situation. Spreading a layer of compost after manual aeration will help to re-establish OM in the soil profile and help to delay the development of future compaction. But it is inevitable and will happen again.

The problem with the sand is that if mixed with clay, it tends to form a sort of concrete with the clay being the cement and the sand the aggregate (gravel in typical concrete mix). Depending on the particle size distribution you have now, it may require a huge percentage of sand to get past the concrete stage. For pure clay, something like 40%. You may need less if you already have some silt and sandy clay. It's not that it doesn't work, but you might have to use a LOT. And sand does nothing to feed the grass, whereas organic matter will improve the lawn and make it more resilient to compaction.

Well guys, I'm taking your advice to heart, but I've been gardening for 50+ years now, so some of it is already in my ROM. I didn't have my current problem until moving to NC. The soil here seems quite poor but the abundance of natural vegetation tends to refute that. In Ohio good loam was plentiful but alkaline, giving rise to practices that don't apply here in (acid) NC. Instead of sulfur, iron, and copperas I now instead buy lime. What is delivered as "top soil" here is simply atrocious.

Anyway I do know that squeezing a handful of moist soil that makes a (non-crumbling) "mud ball" cries for some corrective aeration measures and it is logical to want them to be long-lasting. Moist soil that does crumble when squeezed may not be "permanently" aerated but it is productive and quite gardener-satisfying.

--Close to the earth, DC

The problem is that there is very rarely a quick solution when you are talking about soil.

Yes. Compaction is inevitable. It is the unavoidable result of gravity. The only permanent cure is the aerifying actions of plant (roots) and animal life (worms, burrowing insects, micro-organisms). OM is the single most significant amendment that can be made to soil to promote plant growth and animal presence and counteract the compacting forces of gravity.

For turf, the one thing you absolutely don't want to do is mix in gravel.

Most all those that have advanced degrees in soil science and have spent time studying soils will tell you that adding a bit of sand to clay will not help loosen that clay. To make much difference by adding sand to clay you would need to add about 45 percent sand by volume, a lot of sand.

It also takes a fairly large amount of organic material, 10 tons per acre to raise the level of organic matter one point, to make clay soils workable.

kimmq is kimmsr

I'm not too far from you, just on the other side of those mountains in Tn. (depending on which mountains of course,) and yeah the soil here is rich in minerals, but poor in organic matter. Part of the problem is the climate. It is both moist, and warm. There is A LOT of biological activity. The result is that organic materials decompose into their constituent compounds and elements VERY quickly.

I think there's some good advice above. Aeration, and additions of organic matter are the most effective use of your time and efforts. I'll tell you though, barring regional differences in soil make-up, clay is very nutritious... it just lacks organic matter, drainage and aeration, and soil-nitrogen. Here, where I live, there are a lot of Black Locust trees. Why? Because they are legumes and will thrive where other plants and trees have a difficult time getting started in nitrogen-poor soils. They also spread, not by seeds which require nutritious, moist, loose soils, but through established root systems reaching the surface of the soil. But once the Black Locusts have fixed nitrogen in the soil, drop leaves which create humus on the soil surface, as well as their roots begin to break-up and aerate the clay to allow moisture and drainage, other plants also begin grow and thrive.

So, although the long-warm seasons contribute to a quick decomposition cycle, plant life is quite abundant in those soils that seem 'poor'. In fact, the clay soil isn't poor at all... just the opposite. It simply needs the catalysts of aeration, moisture/drainage, and organic matter to promote life.

Your observations are quite interesting, rgreen. Thanks.

Perhaps my labeling of NC soil as "poor" wasn't really correct, though my moving to NC from loam-rich Ohio led me to that conclusion, seeing all this orange "stuff" which seems devoid of humus. The soil here looks poor to me though it obviously sustains the abundant growth you mention. I'll be adding organic matter to, and occasionally plug-aerating, my area of concern, trying to obtain the rich turf I had in Ohio.

Because of your interest in this topic you may be interested in these two TED talks, which are quite instructive.

https://www.youtube.com/watch?v=8Q1VnwcpW7E

https://www.youtube.com/watch?v=n9OhxKlrWwc

Most clayey soils are not total clay, but a mixture with too little silt and sand in them. I have found sand and peatmoss added to the soil in sufficient quantities to be "yes, instant" relief for hard lumpy areas. I don't have resulting concrete...far, far, far from it but lasting looseness.

Yes soils are different and results could vary. and yes, I believe highly in adding and growing more organic matter.

Clay particles are extremely tiny so just adding sand will not stop the the clay particles from compacting together.

I have added sand AND peatmoss to about 6000 sq. ft. I have added mostly sand to some more area. It all has worked beautifully.

I have clay loam and silty clay loam. Few soils are just clay. Yes, clay particles are extremely tiny. They are the suspended muddy particles in rushing rivers. This clay tends to stay suspended until it hits the salty [sodium] water and then it flocculates [settles out]. Lime will also settle it out.

John, do you have personal experience with adding sand to clay?

Yes I do as a landscaper for many years. I have found that sand can temporarily allow clay soil to aerate and increase drainage but without organic matter it will quickly compact again. It is always best to focus on long term over short term.

"Instead of sulfur, iron, and copperas I now instead buy lime..."

Avoid Dolomite Lime. The LAST thing you need is more magnesium in your clay (makes it even tighter). Use Agricultural Lime or better yet Gypsum.

John, As a landscaper, you probably run into some more heavy clayey soil than most garden soil due to building development. I do agree with lots of organic matter, and do not think that your experience negates adding sand wisely.