Aeration and top-dressing: help needed!

VisualCSharpApril 11, 2012

Hi, folks! First of all, I LOVE GARDENWEB! This site has been so informative and I appreciate everyone sharing their knowledge so freely. This is what makes the Internet great!

Anyway, I've spent the past few hours reading several threads about top-dressing. First off, some facts about my lawn as it currently stands:

- Bermudagrass (Tifway 419) sodded September of last year

- Approx. 4000 sq ft

- Grass is very green but has a lot of white dormant/dead grass beneath the surface left over from last year

Here is what I plan on doing:

- Aeration (rake plugs)

- Top-dress with 50/50 builder's sand/peat moss mix (so-called "pro mix")

My questions:

- Even though my grass is vigorously growing and I recently fertilized, should I scalp it anyway before aerating?

- I've read that organic matter in top-dressing material isn't wise because it just disappears after awhile. Is peat moss the correct material for the 50% that's not sand?

- Can anyone recommend a good company in the Austin/Round Rock area for selling me this 50/50 mix?

- When I buy the sand and it's delivered, I assume they're just going to dump it in my driveway as a gigantic pile. Sound right?

Thanks for any advice, folks! Happy Spring!

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Oh, one other thing that may be important: I have clay soil. In some places it's so clay-ey (hehe) that it's like Playdoh.

    Bookmark   April 11, 2012 at 9:35PM
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dchall_san_antonio(8 San Antonio)

Why are you top dressing? Is your soil below the level of the surrounding concrete and needs to be built up for proper drainage? Answering, "yes" to that second question is the only proper answer to the first. Top dressing for the sake of top dressing or because you watched the commercials from the Master's Tourney can lead to other problems the worst of which is flooding inside your house next time there's a gullywasher. I have a whole soapbox speech about that topic, so careful how you answer. It's even illustrated!

The good news is you have until July to come up with a good answer, because if you try to top dress your lawn before that you risk smothering it. If you are going to top dress, the grass has to be growing its fastest. For bermuda in Austin that is July.

So, why are you top dressing?
Why were you going to aerate?
How many inches were you going to put down?

Yes the material you buy will be dumped somewhere. You will need your own wheelbarrow and shovels. Again you have until July to find those.

How high/low are you mowing?
When did you fertilize last and with what?
How often are you watering and for how long?
How many times have you read the Bermuda Bible?
Where did you read that using a top dressing with organic matter was not a good idea? Frankly I'm baffled by some of the things I read. That must be out of context.

One more thing. Do a jar test on your soil. Fill a straight sided jar half full with soil and take a picture with a ruler next to it. Then fill the jar with water and a few drops of dish soap. Shake the jar vigorously until it seems to be completely uniformly shook. Place it on a level table and wait 2 minutes. Then take another picture with the ruler. After 2 hours take another pic with the ruler. After 2 days take another pic with the ruler. If you can see any daylight through the water on top of the soil after 2 days, then you have almost no clay. The fraction of material that settled in 2 minutes is sand and rubble. The fraction above the sand level is silt. The rest will either be very murky water or clear water.

There other situations besides clay that cause soil to become pliable like clay. Only a good soil test (not from TAMU) will tell you.

    Bookmark   April 11, 2012 at 10:40PM
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I appreciate your response! I don't even have cable so I can't watch the Masters. :)

Anyway, as seems to be somewhat common with new sod, the lawn is bumpy, especially in the back yard. My hope was to lay down a top dress to smooth out those bumps. In fact, I have already done that in one particular spot where water likes to collect and stagnate. My goal there is to build up the elevation a tad so that excess water more freely flows between my and my neighbor's house, along the depression formed by the sod sloping away from our respective houses. My plan was to add no more than 1/2" of top dress. I am prepared for it to take several applications to completely smooth out my soil.

I am currently mowing with a rotary mower at 1.5". I'd like to go lower, but the bumpy soil is making that difficult. I have some slope to my property which means mowing the grass at a consistent height isn't easy. Depending on where exactly the mower is I can get taller or shorter grass. Once the lawn is smoother I can begin mowing at a lower height, probably with a reel mower. My target is 1/2" to 3/4" mow height.

As far as aeration, I did the screwdriver test and it went in pretty much without a problem, so I think I'm going to forego aerating. I think my soil is not compacted.

I performed a soil test several weeks ago. Based on the findings I applied sul-po-mag. Although the soil test showed high levels of nitrogen, I applied Scotts GreenMax for the iron content. My grass has greened up nicely as a result. I am having to mow every 3 days to keep it tidy. Next time I fertilize I plan on using a higher quality fertilizer and verifying it is slow-release; more research on my part here. The test results also mentioned that I need more organic matter in my soil. They recommended a good compost. I have yet to act on this particular finding, however.

As for watering, last year I calibrated my irrigation system for 1" of water per week in all zones--as close as I could get, anyway. I adjusted and will adjust the system appropriately for changing watering restrictions. I verified watering amounts by using ground-level rain gauges. I have the system set for 50% of the regular program because it's not that hot yet. The one depression on the north side of my property is keeping me from fully watering one of the zones. Too much water collects in that depression (another reason I'd like to start to build that soil up a bit). The north face gets almost no sun in a couple of spots and as a result the bermudagrass is thin to non-existent.

I haven't read the Bermuda Bible, but I did see it mentioned in several threads and I will definitely check it out.

A comment or two on one of the threads here had someone say that using compost wasn't good for top dressing because it would eventually disappear. Although I did find that a bit odd (things don't just disappear!) I accepted it at the time. I can only absorb so much at one time, after all! If you've got other opinions on a top dress mix I'd love to hear them.

    Bookmark   April 11, 2012 at 11:11PM
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dchall_san_antonio(8 San Antonio)

Good answer. The problem is semantics. What you want to do is level the lawn, not top dress. They are similar, so there's the confusion.

Click here for an excellent treatise on the subject of leveling bermuda.

The low spot is a problem. Definitely get that built up slowly before you start the leveling (in JULY!!!).

The best tool you'll ever use is called a drag. You can make one with a piece of chain link fence, some rope, and a 2x4 board the length of the fencing you use. Attach the fence to the board and tie the rope to the fencing/board. Then you drag the thing behind you after you apply the sand.

Here's a brief summary:
Bribe some friends to come help you. Don't crack the beer until afterwards.

Get a palate of bags of sand delivered. Get more than you need and return the rest.

Get a push broom for every person there. Rakes are optional. Brooms are required. The drag will save you hours of time.

Fertilize and water a few days prior to scalping the lawn.

Scalp the lawn and go to work the next day.

Spread the sand and start sweeping and dragging it around. When you think you have it like you want it, water it carefully so the sand will settle but not wash away. The water will ruin everything but be patient. Apply more sand and sweep and drag again. Water again. Apply more sand and water again. This should be the last time. I would not expect any more setting after that. Then water it like it was new sod. Water 3x per day (breakfast, lunch, and dinner). Do that for 3 weeks and you should have a new lawn already by August. By October it should be putting green smooth.

I just had a bad thought. Did you rototill before you laid the sod last year?

Back to top dressing for a sec. If you wanted to top dress, then organic stuff is the stuff to use for the simple reason it really does disappear. It is food for the soil microbes and literally disappears as they eat it. It has no lasting volume and so does not change your drainage. Sand or top soil are mineral based. They are permanent and will change your drainage. You are going to cure a problem with sand. That is different from top dressing.

    Bookmark   April 11, 2012 at 11:44PM
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Yeah, I can see how getting the terminology wrong led to confusion. I'll remember that there is a difference in future conversations. Thanks for the clarification!

Thanks for the tips on the drag; I've read about those in several other threads and I've also watched some YouTube videos of folks using a square lute which looked to work very well.

The Bermuda Bible was very informative, by the way.

Unfortunately, I do not know if the builder rototilled before laying sod. I certainly wouldn't be surprised given our soil type (black clay). What would that affect in the leveling process?

The intuitive part of me says "don't scalp the grass while it's growing!" but I guess it does make sense somewhat. Scalping the grass while it's aggressively growing means it's more likely to recover quickly, right?

    Bookmark   April 12, 2012 at 1:22PM
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dchall_san_antonio(8 San Antonio)

Yes, that is why you wait until July. Doing it now will be a problem because it is not growing fast enough.

If a builder put in the grass, he did it right. He hired a decent subcontractor to grade and another one to landscape. What you are experiencing is normal bumpyness for a new lawn. Leveling is definitely what you want to do. Had it been rototilled you could look forward to the soil continuing to settle for 3 years. The lower you can mow the closer to perfection you can get with the leveling process. Sometimes people will plan ahead to level it two summers in a row. It depends on how perfect you want it. "Leveling" also refers to profiling where the soil is not made to be flat but to take on a rolling effect. You need a large area to get an effective profiled effect going.

Do the jar test on your black clay. If you decide to have a soil chemistry test done, don't go to the extension service. Go to Logan Labs in Ohio. They give you a much better test for the money.

Drags are used on a baseball infield before and during play between innings. They are also used in rodeos between events to surface the soil dug up by the animals.

    Bookmark   April 12, 2012 at 2:19PM
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I asked the supervisor who managed my build and he told me this:

"They use a bobcat/front end loader. No tiller."

So it looks like I won't have to deal with much settling at this point.

Thanks again for all the info, dchall.

    Bookmark   April 12, 2012 at 2:43PM
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A couple more small questions:

- Performing the jar test will help determine the correct leveling soil mix to use, correct? Is there any other data I should collect to make sure I use the right mix?
- I should bag the clippings after scalping, correct?

    Bookmark   April 12, 2012 at 3:06PM
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dchall_san_antonio(8 San Antonio)

Awww geeze! I take back what I said about them hiring a decent subcontractor. He ended up losing money on that deal. A Bobcat can do in a week what a tractor and box blade can do in an hour. I'm not kidding. He went with the lowest of low bidders on a per hour basis. Then they brought in a bobcat and shot the hours up to 40 instead of 1/2. That's water under the bridge. Your soil may settle for another year or so simply because the bobcat approach is so inefficient. Once you learn how to do this, you'll be doing it all the time ;-) Take lots of pictures.

The results of the jar test will change your mind about calling your soil 'clay.' That's about all. I'm not sure there is enough clay in Texas to fill your lot. But it will help you to move forward once you realize you are not dealing with clay but something else. I understand the texture is much the same as clay, but I'm saying there are mixtures of minerals which seem like clay but have no clay at all. The jar test may befuddle you to the point where you actually do send a soil sample to Logan Labs to see what it is that makes it act like clay. The answer rhymes with fragnesium.

Sand is still the right thing to use for leveling. If you use "topsoil," it will come to you with clods bigger than the holes you have right now. You cannot level to 1/4-inch perfection when the clods are 2 inches across. That and shoveling cloddy material will break your back. You get into a groove of pushing the shovel into the soil and there's a clod. UGH! Your back tenses up and you lose your groove. Bagged sand is what you want. Look for masonry sand, not play sand. Coarse is good if you can find it. Not as coarse as fish tank sand but coarser than sugar sand...if you can find it. Something like 80 grit sandpaper. The best sand for this is chipped sand - not river bottom sand. River bottom sand is made of particles rounded by eons of tumbling around in the river. Chipped sand is more recently broken from other rocks. It is often a byproduct of stone cutting. Chipped sand will interlock to make a firm footing. Roots will help but there's nothing like a locked in subsurface. Get what you can locally. Just know what you are looking for.

Yes about the clippings. Bag them and empty the bags on your compost pile.

    Bookmark   April 12, 2012 at 10:09PM
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Thanks again for the detailed info. Seeing as San Antonio just reimposed watering restrictions, I'm going to take this leveling thing with a "grain of sand," hehe. I might not do it if the drought comes back. For now, the lake in Georgetown is full. Fingers crossed!

    Bookmark   April 13, 2012 at 5:49PM
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