The big soil questions (new lawn)

Lawn_HobbyAugust 3, 2012

Ok, I have the chance to get a fresh start in one area of the yard. Right now, it's just soil and some pebbles (and a couple of weeds I'll spray next week). I have submitted the soil for analysis, and was told I should have the results back in two weeks. But I have a feeling that the soil has no fertility whatsoever, and will be lacking some minerals possibly as well. We'll have to wait and see.

But, what are my options? Initially I was thiking of bringing in topsoil and a bit of compost. But are there other options too? Note, I don't have a year or two to wait for the soil to stabililize. I need grass this fall.

I also read some recent posts on avoiding tilling due to formation lumps. I don't want uneven ground so I guess I can't till (actually it's already unven but that's another story).

How can I work amendments into the soil without tilling? All my soil is sub soil. There is no topsoil whatsoever. That's why I think it won't test out very well.

Please advise.

Thanks as usual.

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Except for OM, you wont be adding any other amendments until you get the test back. Now is the time to get it level by knocking down high spots and filling in low spots and making sure you have proper drainage.

    Bookmark   August 3, 2012 at 4:30PM
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How am I supposed to go about this leveling? I feel I'm going to need some sort of power equipment, as the top layer is too hard to do it manually. And the rocks are in there, too.

I should add that the soil that is now on the top layer is soil that was 6 feet underground before. It's light brown, and full of rocks. This was due to excavation.

btw, what do you mean by OM? Not familiar with that abbreviation.

And how to ensure drainage? It slopes down a hill. That should be good enough.

Finally, when I do mix things into the soil, how am I supposed to do it without tilling it into the top layers? Again, doing it with a rake is out of the's too hard/compacted on top.

    Bookmark   August 3, 2012 at 6:42PM
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It's full of rocks? Not soil with some pebbles? I assumed it was good enough that you were considering planting in it as you had it tested. Almost any old dirt can be made into soil by adding NPK, micronutrients that it is severly lacking in and OM (organic matter - it helps in retaining water and gives soil its tilth)) SOME pebbles aren't going to be too much of a detriment, but grass wont grow on rock and too many pebbles would make the surface too rocky to grow a good stand of grass. It would also be uncomfortable to sit or kneel in and too many pebbles at the surface or rocks can have other disadvantages like lawn mower blade distruction and holding too mcuh heat in the soil. So if your dirt is too rocky to support a lawn you might as well bring in sifted topsoil, get the yard leveled and drainage addressed and then get another soil test of the new topsoil.
As far as leveling and drainage, I wouldn't presume to advise you on how to do it without knowing what it looks like--it could vary from using a hand rake to a box blade to a buldozer. For small areas of fill, sifted topsoil or sand can be used.
My lawn is planted in subsoil (new construction and what soil was trucked in had long ago washed away and the builder just ended up hydroseeding most of which also washed away--so the neighbors tell me.) I used sand to fill the gullies and level it. Building a lawn on subsoil can be done, but I'm still picking pebbles and small rocks out. If it had been an option, I woiuld have probably trucked in topsoil, but there was no way to get a truck in the back and I wasn't about to wheelbarrow it or pay to have it wheelbarrowed and the front wasn't too pebbley anyway. I added OM (organic matter) by aerating and topdress/dragging compost.

    Bookmark   August 3, 2012 at 8:36PM
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Yes, I do feel that bringing in topsoil would the most efficient way to do it...that is what I was going to go with. But then everyone is recommending against tilling. My Scotts lawn book says to till the topsoil into the subsiol to eliminate sharp transitions and compaction. So maybe with sufficient topsoil and tilling it will actually provide a better, more even surface than what I have now. Certainly, it would be a better medium.

I also want to sprinkle a dusting of compost into that trucked in topsoil and then mix everything together. Whatever else the soil test tells me I need (eg. Lime, sulfur, iron...) I will also mix into that layer that gets lightly tilled.

The jar test sounded like a good idea, but I'll wait for the soil test results. That should be better.

Now, how to evaluate topsoil and compost for purity? My neighbor's lawn got destroyed over the past few months by compost contianing crabgrass seeds.

    Bookmark   August 3, 2012 at 9:56PM
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Good ol' Scotty needs to straighten Mother Nature out, it seems she's been doing it wrong for eons with the sharp transitions.
Most advise against tilling for a number of reasons: 1. if the soil is too moist or if it is a hard soil==high clay or magneseum content, tilling will create clumps. 2. tilling adds air and it can take years for it to settle unless it is very sandy soil. 3. tilling can pull up tons of weed seeds. (I've only seen one lawn tilled and seeded. As it was very sandy soil, 1 and 2 were no issue, but the weeds, I've never seen so many weeds in a lawn) In your case you are adding a 4th problem. What are you going to do with all that rock you are going to pull up?
Good compost will not have weed seed as the composting process will kill them. Good compost will have no visually identifiable organic matter in it. The only odor will be a very earthy smell--otherwise you can send a sample to be tested for weed seed. Other than having it tested, there is no way to determinse if topsoil is weed free.
Good luck with your reno, I do hope it all works out for you.

    Bookmark   August 3, 2012 at 11:28PM
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So, the fact that the subsoil is rocky, uneven and compressed on top does not matter? Now, my book also recommends 4 to 8 inches of topsoil! This would be a huge amount, impossible to afford, and impossible to spread in the span of a week (8 inches worth).

What am I trying to do? Am I trying to grow the grass just in teh topsoil layer initially and then the roots will eventually pierce through the tough crusted subsoil underneath? I'm not sure I completely understand how this all is supposed to work with the various layers.

    Bookmark   August 4, 2012 at 12:05AM
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And several other things...

The soil already has air in it. Remember it was all mixed up totally by excavation equipment during the construction phase.

The weed seeds are already on top, and the few weeds that are growing can be killed with Roundup before planting.

The book says you can ruin the soil structure by tilling if the soil is too dry or too wet. They explain how to test it to make certain it isn't. Then they tell you to till it to mix everything as I stated.

I still don't quite see how to form a uniform soil without mixing it.

    Bookmark   August 4, 2012 at 12:09AM
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Lawn Hobby,
I was able to grow a decent lawn on subsoil. You may not be able to. If I had determined that my soil was too rocky to be a good base, I would put an inch or two of topsoil down and planted in that and now, a couple yesrs later, I would get a soil test and start amending if needed.

Most everyone advises against aeration and they give good reason not to. I aerate when in my opinion it is called for. I weighed the pros vs the cons and decided that the advantage I wanted from aerating outweighed the disadvantages. It's worked out for me, but may not work out for others.
Lawns are not an exact science. You collect what information is available and calculate your odds and place your bet based on reducing as many adverse variables as possible. No one on this board can guarantee success. If you determine that the advantages of tilling outweighs the disadvantages, go with tilling. Neither of us know for certain what the outcome will be. If you till I truly hope it works out for you, no one here is rooting against you.

    Bookmark   August 4, 2012 at 2:13AM
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"So, the fact that the subsoil is rocky, uneven and compressed on top does not matter?"

Sure it does, If it is too rocky to be a good base, then add a layer of topsoil over it. That is your call from your obsevations. As Ive said I've got a decent lawn on suboil--glacial deposit.

"Now, my book also recommends 4 to 8 inches of topsoil!"

Idealy, Yep, the root zone is commonly in the first 6" of soil. Some fescues root to 2 feet. Bluegrass commonly roots in just the top 4" or less.

" This would be a huge amount, impossible to afford, and impossible to spread in the span of a week (8 inches worth)."

That is one of the factors that I weighed heavily when I decided to grow turf in my subsoil. Once again, your call based on your observations of the soil that is there. Because of the gravely consistacy of my lawn from 2-3 inches down, it is very sensitive to heat and I most monitor watering closely, but water for me is realitively cheap, especially vs the cost of hauling in 6" of topsoil. My opinion is you need 2' inches of relatively stone free soil for the turf. I'd say no more than 10% pebble vs dirt. Otherwise add a couple inches of topsoil. Once again, I was able to grow a decent lawn, but I'd say I had two inches of dirt that was no more tha 10% pebble. Bellow that it is about 50/50 dirt and rock.

"What am I trying to do? Am I trying to grow the grass just in teh topsoil layer initially and then the roots will eventually pierce through the tough crusted subsoil underneath? I'm not sure I completely understand how this all is supposed to work with the various layers."

It's not ideal, but yes that's what you will be working for- the alternative is bringing in 8" of ropsoil. Plant roots are increadibly strong--ever seen where tree roots have raised sidewalds or broken up a concrete drive? If you supply the turf with needed nutrients and water it will eventually convert any dirt into soil over time.

    Bookmark   August 4, 2012 at 3:24AM
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Well, I'd love to not to have to till. It's a ton of work and won't help my allergies. So I like hearing not to do it. The grass in that area is going to be 90% tall fescue and bluegrass, and 10% ryegrass. So assuming the tall fescue wants to root down at least a foot, will I be preventing it from being able to do that?

    Bookmark   August 4, 2012 at 2:35PM
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btw, we'll try to go with 4 inches of topsoil...bare minimum required amount.

    Bookmark   August 4, 2012 at 2:38PM
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I don't consider myself anywhere near a good enough student of turf to answer that. As I've implied earlier, I try to pass on information that I've read and feel reasonably confident is accurate and what I've learned from my own hands-on experience. My own lawn is elite KBG, but I do have small area that is dominated by fescue from the original turf and during the taking of soil samples, I pulled the sod up. The fescue area roots did appear to have grown deeper into the gravely layer that starts two to three inches below surface than the KBG, but nowhere near a foot - maybe 2-3" into the gravely dirt where my KBG appears to not root very much at all into the stoney layer. Although the fescue appears good and healthy, it along with my whole lawn is sensitive to heat and drought due to the stoney nature of the soil and the overall shallow rooting. As a result, I need to water a little sooner and a little longer than my neighbors during periods of drought or high heat. Still, for what it is worth, per my neighbors I have the best lawn in the hood.
Hope that helps.

    Bookmark   August 4, 2012 at 3:19PM
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Well, these photos should help.

Here is the overall view of the subsoil:

Here is a closeup of the large rocks using my fingers as scale:

And finally one showing the pebbles:

The soil is so compacted I actually twisted/bent my brand new soil corer when taking the sample, and had to resort to a trowel. It was not easy to do.

Still looking for suggestions on how to directly deal with this for grass growing.

    Bookmark   August 4, 2012 at 4:57PM
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Wow. For perspective: In the picture of "pebbles", my "topsoil" is very similar to what is in the area to the right and above of your index finger, some areas maybe slightly less stoney. My soil that is three inches below that, looks very much like the ares in the top left corner of the same picture--the area above and to the left of your ring finger. I had a number of stones that were at surface level, 30- 40 that varied in size from tennis ball size to volleyball size that my wife used for flower bed edging and also 7 carry on bag sized stones. Your first two pictures reflect nothing in my experience. I don't see where you have any option other than to clean off the stones on the surface and put topsoil down. Maybe someone with experience with this situation will chime in with some advice. Your "soil"-what isn't stone- looks very similar to mine, sandy silt--doubt it has much clay content. The soil test may show high magneseum which would explain its hardness.

    Bookmark   August 4, 2012 at 10:18PM
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I was thinking of clearing more stones away from the surface, but you have to remember there are also more underneath those. So, I guess the topsoil layer is going to have to be pretty least 4 inches, even with the surface stones cleared away first.

Some stones in the soil are good because they help the roots take and keep hold and prevent errosion. But obviously, too many will prevent proper rooting.

This is Connecticut we're dealing with. I'm sure tiemco is used to this.

    Bookmark   August 5, 2012 at 12:27AM
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Lawn Hobby,

I've read your other posts and based on those and this post I have the feeling I'm getting my chain yanked. If I'm wrong I apologize, but I'm going to bow out on responding to furthar posts.

    Bookmark   August 5, 2012 at 1:40AM
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dchall_san_antonio(8 San Antonio)

Pictures are definitely worth 1,000 words. I was about to suggest you were trying to make excuses for not just putting down some seed and toughing it out.

Now that I see what you're dealing with (river bottom rubble), if you can reschedule and rebudget your lawn, I would drag that stuff out and replace it with anything from sand to screened topsoil, or "landscapers mix". The least expensive way would be to sift your current soil to dispose of the rocks and use that. You can improve your soil from the top. It does not have to have amendments blended in. But I think you need to get rid of at least the larger rocks.

You might check into getting a landscaper to give you an estimate on sifting the rocks out. He may want to scrape them out and replace with better soil. That's okay but get an estimate to do it both ways.

If you are starting with your same, sifted, soil, then you can get going on fixing it with water, shampoo (to help the water soak in), a little bit of compost on top (NOT TILLED IN), and some organic fertilizer. Mother Nature fixes Her soil from the top. When we try to jump start things, it usually does not work like you expect. Spray some clear shampoo at a rate of at least 3 ounces per 1,000 square feet and immediately scatter the compost and organic fertilizer. Then immediately irrigate another full inch to carry the soap in. Repeat the shampoo again in 2 weeks and your soil will be on its way to recovery. Then irrigate once a week in the summer and once a month in the cool months to keep the soil microbes moist. That should get you going.

    Bookmark   August 5, 2012 at 3:15AM
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You know, guys, there were even more rocks before. Our contractor actually cleared the larges ones away with a rake last month!

Here's what I'm thinking of doing: The week after next, I'm going to go around with a trowel and hand pull as many of the larger rocks as I can. I will have the time, so why not do it?

And then I'll follow your directions, dchall.

But a few more questions...what sort of shampoo am I looking for? Is baby shampoo the best? I have some concerns about it in the environment (though I guess it's nothing bad compared to the glyphosphate I've been using the past couple of weeks).

Now, before I proceed beyond the rock cleaning step, I'll post the soil test results for this area (I submitted in total 7 samples from different areas in the yard for testing).

Finally, for now, what do you think would be the earliest I could plant grass in this area? I'd like to do it by early September at the latest.

Thank you.

    Bookmark   August 5, 2012 at 9:44AM
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By the way, dchall:

After taking up surface rocks, spraying with shampoo/water, and putting down organic fertilizer and compost, I would still bring in 3 inches of topsoil if possible. Can I just put that over top of the compost/fertilizer layer when I do? Or is tha the wrong layer order?

    Bookmark   August 5, 2012 at 9:55AM
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dchall_san_antonio(8 San Antonio)

Three inches of anything will change your drainage considerably. Be sure you are not going to back water up to the house when it rains.

Put compost on top of the new soil, not under it and not incorporated in it. I realize I'm probably the only one to say this but I believe burying compost is a mistake. Compost is the undigested remains of organic material. It seems that when you get to the stage of being really hard to decompose, exposure to the air is important in the final decomposition process. For example the fungi that decompose wood must have adequate air or they will not decompose anything. It is my belief that compost must be exposed to the air in a similar way.

I would apply the organic fertilizer on top of the topsoil, too for similar reasons. In Mother Nature's world, She always applies compost and dead stuff to the surface.

The shampoo can go down on the bare dirt.

You can plant grass seed now if you want to. I don't see any reason you cannot put it down the day you put the topsoil down. Be sure to roll the topsoil and drag it to get it level. Search this forum for leveling and drag.

Baby shampoo is not the best. Any clear shampoo is likely to be equally good. The cheaper the better because they will have only the very basic soap ingredients. These clear shampoos are made from relatively harmless coconut ingredients. I suppose you can find harmful materials in coconut, but these seem pretty safe.

    Bookmark   August 5, 2012 at 12:16PM
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Great advice.

So, what compounds am I looking for on the shampoo label that will help solubilize the soil? There are so many shampoos out there with various ingredients. Is it the coconut products specifically, or something else?

    Bookmark   August 5, 2012 at 1:58PM
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