Old Sawdust

[kyrustic]

I have access to tons of very old saw dust. Would it be ok to work this into my garden? What uses would it have

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[Phisherman]

Yes. If the sawdust was left outside for a year, then it can be worked into the soil without concern about robbing nitrogen. It makes a good mulch for tender shallow rooted plants such as blueberries and azaleas.

[Fito]

Phish, rather than disagree with you, let me ask a question as I am not sure of the answer. Does the sawdust lose it "Nitrogen stealing" ability as time goes by (meaning, is the C:N ration no longer 500:1)? Even after a year, if it did get weaker, wouldnt it still be high in carbon? Still too high to be placed in soil?

My initial response would have been to use it as a water retaining mulch.

Thanks in advance, Fito

[kyrustic]

This sawdust has been weathering for years. I'll give it a try. Thanks

[Snooze]

Sawdust doesn't rob the soil of nitrogen, sawdust just temporarily reduces the amount of nitrogen compounds available to the plant. The bacteria and various other microorganisms that consume the sawdust use the nitrogen in the soil to live. When these various microorganisms die, they release the nitrogen back into the soil.

You didn't say if you were going to use this around ornamental plants or vegetables. Is there a concern that some of the sawdust is from pressure treated wood? If so there are chemicals in there, that aren't desirable around food plants.

Sameer

[Phisherman]

I can't provide a scientific answer to this, but here's what I know first hand. I applied some sawdust (aged 2 months) to a blueberry bush as a mulch, and it weakened the plant with loss of green color. (Later, I revived the plant using MirAcid fertilizer.) The following year, I reapplied sawdust which was aged for 14 months and this had no adverse effects when used as a mulch. My assumption is that sawdust aged enough declines in its nitrogen robbing properties. I am a woodworker, so I have a lot of available "time-laddered" heaps that are decomposing for use with blueberry and azalea bushes. The sawdust is also good to use in muddy areas, horse stables, walking trails and under decks. If new sawdust is mixed with grass clippings in a 50:50 mix, it makes an ideal start for a compost heap.

[nswong]

Hi Fito,

I'm also not sure of the answer.

From what I read, it give me an impression:

All life need carbon as energy, and need nitrogen to grow and reproduce. Life in the soil normally will be in maximum constrain by the available carbon. When we mix sawdust to soil, the available carbon will increase, those life in soil will start to use available carbon from sawdust as energy to reproduce. When life in soil reproduce, they get nitrogen they need from soil, so available nitrogen in soil will reduce. These nitrogen will release to soil when life in soil die and decompose.

Carbon in available form(sugar, starch...) are plenty in fresh sawdust, it will lost when time passby. Carbon still remain in old sawdust are those(cellulose, lignin...) that are not directly usable by most of the life in the soil, so this will not cause the suddent increase of soil life.

Adding sawdust to soil will temporary reduce available nitrogen(change to organic form), but not reduce nitrogen from soil.

So for organic matter add to soil to improve soil structure, I will prefer lignin than other form, since lignin last longer. And I believe that clay humus created from clay plus lignin, are the best humus.

Regards, Wong

[Mike LaMana]

Folks:

1.) Be aware that the starting chemistry of the soil i questions and the starting chemistry of sawdust both play a role in answering the original post. 2.) C:N ratio is critical but can be misleading. For example, the C:N ratio may be the same for raw sawdust added to soil and for highly composted sawdust added to soil. One critical difference is with the latter a lot of the C (carbon) will be accounted for in humic acids which are chemically recalcitrant and do not really figure into the resources needed by soil microbes. In raw sawdust most of the C is accounted for in long-chain carbohydrates which are convertible. 3.) The use of sawdust to amended pH in blueberries is well established, but bear in mind that blueberries are commercially grown only in certain soil types. Thus, examples from that use may not extrapolate well to other (e.g. more alkaline) soils 4.) Depending on the sawdust, one may actually make the soil more alkaline.

[Sue]

How much of the "tons" are you planning to work into your soil???? How big is your garden?

Vegetable or ornamental?

What type of soil you you have to start with? What effects are you expecting from the sawdust application?

Have you done any soil testing?

I do use sawdust as a mulch on my asparagus. 10 years ago I started the bed in sandy loam amended with rotted horse manure. Rather than "trench" the bed, I started from seed and transplanted at the soil level. I then built a low rock wall around the bed, about a foot high. Mulch has been added rather "at will" over the course of the years and now the bed is full to the top of the wall. The mulch has been primarily sawdust, leaf-litter, wood ashes, coffee grounds, compost when available, and an annual sprinkling of whatever garden fertilizer I have on hand.

The coarse, friable nature of the mulch makes weeding the asparagus bed in spring a quick, easy job. Any weeds that encroach are shallow rooted and easily yanked. The asparagus roots are 14+" below the surface, I'd need a backhoe to get them out now.

[Beecrofter]

composting things like fish wastes dead animals and chicken manure. Worked into the soil it would provide organic material (mostly carbon) but you would need to provide some supplemental nitrogen to the crop.

[philosopher]

For the benefit of newbies out there--do NOT do this with pressure-treated lumber sawdust!

philosopher

[David J Bockman]

Just as an example of how valuable sawdust and other organic material can be, sawdust was used (dozens of tons of it) in conjunction with sand and human waste to help bioremediate a truly scary landscape, that being the former Seattle Gas Works, now the lovely Gas Works Park.

Several weeks ago I listened to the principal designer of that park, Richard Haag, give a talk about the site. The 'soil', if you can call it that, was simply industrial waste piled 5-10 feet thick in places-- 'Industrial Afterbirth', he calls it (while acknowledging the melodrama of such a label). In the mid to late 1970's Mr. Haag oversaw the beginning steps to remediating that horrorshow, first by introducing bacteria that would start to heal the space and second by slowly, over time, increasing the soil's fertility. The initial steps were the laying of tons of sawdust from nearby lumber mills, tons of human sewage, and also tons of sand, all of which was turned into the space as deeply as possible (think 'double digging', but with bulldozers).

A good history of the space can be read at

[Kenneth]

Howdy,

There are advantages, but adding sawdust will (radically) deplete the area of nitrogen...

HTH,

[simy1]

This is against my experience. My front flower bed, for example, has only received one foot of woodchips since 1996, and its N content is OK, and the plants growing in it show no sign of being N-deficient. The surrounding soil is extremely N-poor. I must conclude that decomposing wood absorbs nitrogen from the atmosphere.

could you comment on this, as well as point 1)? How is the sawdust chemically different?

[nswong]

Hi simy1,

I assume it's a sandly soil and lack of organic matter to buffer nutrient.

Some bacteria will fix nitrogen from the air, provided there is carbon available as energy. The carbon can get from exchange from legume, or directly from soil. When the bacteria die and decompose, nitrogen will release and available by plant. Some nitrogen will come from storm. All this will return to air if there is nothing to hold it.

A lot of nutrient are keep in soil in life form, semi-decompose dead body, either plant or animal. This act as nutrient bank that buffer nutrient.

One thing I'm not quite clear, can fungus be group into plant, and bacteria into animal?

Regards, Wong

[eclectic]

(snip)

My understanding is that neither fungi nor bacteria fall into the plant or animal kingdoms in a five kingdoms naming system, (they each would reside in separate kingdoms). In a three divisions naming system, plants, animals and fungi would be described as belonging to the same domain.

Regards.

[nswong]

Hi eclectic,

Thanks for your clearing. :-)

So my previous sentence should read as:

A lot of nutrient are keep in soil in life form, semi-decompose dead body, either plant/animal/fungi/bacteria or protozoa.

Thanks, Wong

[Salty Thumb]

"eclectic" wrote in news:Klfkc.21844$k%. [e-mail]:

if you go by the microbiologists, I believe they go with 3 kingdoms (superkingdoms ?), two kinds of bacteria and everything else, based on genetic studies. But if you go with biologists (according to _Five Kingdoms: An Ilustrated Guide to the Phyla of Life on Earth_, 3rd ed. 1998, Margulis, Lynn and Karlene V. Schwartz), the five kingdoms are bacteria, protists, animals, fungi and plants. (I have no idea if the book has any currency with real biologists and I certainly am not one.)

[Pen]

What about the new treated lumber which are arsenic and chromium free? Can the copper (ACQ) preservative be toxic? I've found these articles that I'd like to share: