Does tree sawdust affect lawn?

timjcNovember 28, 2007

I've just had a huge oak tree that was hanging over the house removed and there's a lot of sawdust on the lawn. Is this a problem for the lawn. I'm planning to remove as much as possible, but I'm wondering about the acidic affect, etc. I just limed recently.

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jer213(5/6 IL)

I can't speak about the acidic effect, but I do know that it will leach N from the soil as it decomposes. Sawdust is a great addition of organic material, but you'll need to add some fertilizer to counteract the leaching so you don't starve the grass.

So you can spread out the sawdust and spread some fertilizer too wherever you spread, or throw it all in your compost pile (if you have one), or sprinkle it on dog poop (and pee too) to keep it from burning the grass and to make it break down quicker.

    Bookmark   November 28, 2007 at 9:59AM
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lou_midlothian_tx(z8 DFW, Tx)

You can use blower to spread them as thinly as possible and pu t down soybean meal at the rate of 20lbs per 1000 sqft. It works great with rotary spreader. it should help break down sawdust faster.

    Bookmark   November 28, 2007 at 12:16PM
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I keep reading about the use of sawdust in gardens and in compost. In compost I can readily understand that if its spread out, it can decompose quickly. And too, I understand it will (as wood does), take nitrogen from the soil (or the pile) to effect breakdown and an occasional handful of lawn fertilizer thrown in can supplement.

But, if thrown into a garden or on a lawn where it can mass itself when absorbing moisture, is I think letting it mat down, rob the soil of nitrogen in a very small area and lead to problems.
So I'd say to get out as much as I could with however means or at least, with a fan rake spread it so thin to lessen the problem.

I suppose too throwing down a nitrogenous fertilizer over it will help it break downa and give back to the soil some nitrogen.
but you say you have given it lime. The lime, depending on just what kind of fertilizer, can be neutralized by the nitrogen. I know urea type should not be used without at least a month in-between applications of lime and fertilizer. But you can do a Google search on that aspect.

All in all, I'd say don't worry about acidity from the sawdust, the lime, if not given too much, will neutralize that. Between the fertilizer and the oak sawdust, hopefully the lime will do what you hope it will do.

    Bookmark   November 29, 2007 at 10:03AM
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dchall_san_antonio(8 San Antonio)

Sawdust really only "robs" nitrogen when it is buried underground and cannot get nitrogen from the air. Sawdust is decomposed by a fungus, so you want to do everything you can to allow fungal growth. Moisture is imperative. Steady moisture is best. I like to use a mister over my compost pile to encourage fungal growth.

If you have so much sawdust that you cannot see the soil underneath, you might want to rake, sweep, blow, or hose the sawdust around.

Many years ago a guy wrote into the soils forum to discuss his experience with adding inches of sawdust to his garden soil every year for 10 years. He started out with ceramic quality clay and after several years ended up with soil so full of organic life that he could plunge his arms into it to the elbows (his words). I don't know how deep it was but he had enough detail to convince me that applying sawdust over time would develop a population of fungi that would rapidly decompose the wood.

    Bookmark   November 29, 2007 at 9:10PM
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deerslayer(Z5 NE IL KBG)

I agree that wood chips rob nitrogen from the soil.

In addition, wood chips made by a chainsaw are often contaminated with chainsaw bar oil. The premium bar oils are 75% or so sunflower seed oil and about 25% dino. The cheap bar oils are 100% dino or worse yet, reclaimed motor oil.

My chain saw has a .6 pint bar oil tank. I can go through several tanks sawing up a tree.

I think that it's best to pick up as many of the chainsaw chips as possible.


    Bookmark   November 29, 2007 at 10:39PM
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whip1 Zone 5 NE Ohio

If it was my yard, I'd speard them out thin, and proced with my normal lawn care schedule.

    Bookmark   November 29, 2007 at 11:41PM
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timjc, the only disadvantage that I can think of is that the vegetation will show a nitrogen deficiency (except, possibly, if it is a 'legume' crop). By all means spread it out over as wide an area as you can (1 to 2 inches thick would be desirable). It will benefit the soil in a 'permanent' manner. Watch the color of the grass, compared with an untreated area. If it begins to get lighter, then you might want to add some nitrogen, preferably ammonium sulphate. You might need to use additional nitrogen in the next year or two.

    Bookmark   December 1, 2007 at 7:49AM
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lou_midlothian_tx(z8 DFW, Tx)


Ammonium sulphate will cause damage to soil life esp fungi and fungi is needed to break down wood based materials. I'd go with soybean meal. Much better.

    Bookmark   December 1, 2007 at 6:54PM
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lou midlothian tx, I was remembering this quote from a text book (I think).
"Soil microbes attack the sawdust/bark as soon as it is incorporated into a soil. The microbes use nitrogen as an energy source as they attack the organic materials. Gardeners must add one pound of nitrogen (e.g., five pounds of Ammonium Sulfate (21-0-0) for each 100 pounds of sawdust/bark material incorporated into the soil to compensate for soil microbe needs".
Evidently the microbes do not care where the nitrogen comes from.

    Bookmark   December 1, 2007 at 7:19PM
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dchall_san_antonio(8 San Antonio)

ronalawn82: I've seen that too. The first two sentences of that statement are the fundamental basis for what Lou and I have said.

    Bookmark   December 2, 2007 at 5:40PM
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lou_midlothian_tx(z8 DFW, Tx)


Are you sure it's really the ammonium sulfate breaking down the sawdust, not feeding the plant directly? I have my doubt after what I've read for the past few years.

    Bookmark   December 2, 2007 at 8:23PM
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