Looking to set up a mill shed on a 1-acre lot. Wanting to spread the excess sawdust on a neighbor's farm but would like to provide him reliable data and not hearsay stuff.
Many a familiar with the poplar view that spreading sawdust, or any wood waste, on soil will deplete the nitrogen during the decay process. But at a certain point in the decay process the nitrogen returns to its original level.
I find this a bit nebulous. I'm looking for more details. Has anybody got any links to real scientific studies?
I can't help you out with any brainy techy type stuff, just some old authentic country jibberish hear-say :D I don't know how much sawdust you'll be spreading on how many acres, but, right here I have a few places i've dumped & spread it, a foot deep to cover up some rocks. By late summer, the grass & weeds are growing up through it. The following year, you can't really see it & it gets covered again. I can't imagine it's hurting or keeping anything from growing, it's all organic, after all.
I would head to the bookstore and look this info up in a few organic gardening books. I've used sawdust in my own backyard garden, but on a limited basis, because according to one book I read, too much sawdust can change the pH balance of the soil, especially depending on the type of sawdust you use. I don't have any of the specific information in front of me, but I know I've read about it in several gardening books, and they all cautioned against using too much, but used in the right kind of dosage, it's great for soil.
You have to be careful as to which type sawdust you spead as previously stated. ie walnut sawdust holds a toxin that will prevent anything else from growing.
Stew
Too my knowledge the sawdust simply ties up available nitrogen during decomposition them lets it go. A neighbour mixes his in with manure which is rich in nitrogen.
The other option is to mix it with manure and let it compost before spreading it. That is what my sister does. It makes a very risk material that all the gardeners chase after. The horsey stuff is a bit less popular than the sheep stuff but still works well.
I would think most sawdust is fairly ph neutral but barks are not, there are tanins that are acidic. Don't know if you are chipping slabs too?
What happens is the nitrogen is immobilized due to a high C:N ratio. This does not allow for the nitrogen to be broken down to ammonium. Add manure to your mix, and you'll be OK.
Before you think I'm really brilliant, I got the info here:
http://www.ext.colostate.edu/pubs/crops/00546.html
I don't have the specifics, but sawdust is very acidic. I use it on Blueberrys and they love it.
Here is a study (http://www.tnstate.edu/iager/seminar_abstracts/dennis01.htm) that says that sawdust making the sail acid is an "old wives tale". You read it and make up your own mind.
The way I read it, soil gets to the pH of the sawdust in about 6 months.
Stew, i've heard that about Walnut too, but I don't buy it - I use a seperate bag for walnut planer shavings, so they don't get sent to the horse barn [they are bad for that] The walnut gets dumped out past my logs, weeds & everything grow right up through them. My walnut trees too, grass, weeds, whatever - They get trimmed around as much as any. There may be some species of plant that doesn't "do good" around walnut, but in general, I don't see things dying around them.
Quote from: mike_van on February 26, 2007, 03:14:16 PM
I can't help you out with any brainy techy type stuff, just some old authentic country jibberish hear-say :D \
I grew up on that stuff! lol But there is almost allways some good truth to it. After all, any good farmer will tell you that it adds organic matter to the soil and this is almost allways a good thing.
Thanks for the reminder on the walnut sawdust. We may have to charge a little extra for sawing walnut to cover the trouble of keeping it separate...then spread it only in grassy areas.
Mixing that manure with it is an excellent idea. I've always been a fan of this idea. You're sure to off-set any problems...real or percieved.
Thanks for the links. I'll check them out soon.
BTW - The neighbor has a dairy operation. He spreads his manure with one of those giant center-pivot manure irrigation systems. This area he uses to grow corn, milo, tobacco, soybeans and alfalfa. He also has other alfalfa hay fields, pastures and wood land. He's an umteenth generation farmer that probably knows much more about this than me. But I wanted to be prepared to address any problems he may percieve before I talk to him.
I've found that broadleaved plants don't do well under black walnut. In my plantation (3 acres with about 750 trees on 10 x 10 spacing) there are a few plants other than grasses that will survive there, like black raspberry. But for sure won't leave the place barren. I still have to mow a couple times a summer. Used to keep it disked and tilled, but I determined I was too rough on the roots. So when the trees grew up a bit, and had good shade, I quit tilling and just mow now.
Don't try any tomato plants under a black walnut, as they don't do well there. :)
Might try getting ahold of a soil scientist somewhere near, and ask about the nitrogen depletion. I've heard it, but don't know nothing more bout it. :) Years back, friend of mine tilled in sawdust on his clay soil, to build it up over time. He said he needed to add a lot of nitrogen to speed up the breakdown of the sawdust. I believe he did some soil testing as he progressed. Certainly made a fantastic soil for his lawn after 3-4 years.
I found both my shavings and sawdust from white oak pretty much killed the weeds back for a good time in my driveway or anywhere else I sawed and laid out the waste. Probably the tannin in the bark. After a good rain you could see the brown water in the small pools.
I found out it is a poor way to fill in a hole, turns it into a muck hole that is tough to drive through. Seems to retain the water better. After a year or two it is walkable where the grass ended up growing though it did not fill in any holes much, if anything. No sub. for dirt and rocks.
http://www.ext.colostate.edu/pubs/crops/00546.html had a comment about wood residue releasing toxic compounds upon decomposition. But they didn't state what those compounds were or in what amounts. (Maybe we ought to cut all the trees down in the world and bury them in a toxic waste dump. :D) I think nature will take care of itself on this one so long as you don't overdo it.
The second thing that bothers me is they seem to want to push you to augment the temporary nitrogen loss with fertilizers. Contrast this with their claim that the nitrogen naturally returns to its original level + a little more and I'm wondering if they secretly work for the fertilizer companies. In other words: do nothing and come out ahead or add expensive fertilizers and come out ahead.
The second link http://www.tnstate.edu/iager/seminar_abstracts/dennis01.htm had a good idea but did not publish the final results. But they did speculate. ???
Not real scientific and I know my mother was ballistic. Years ago my dad build a tree nursery for the govmnt in Alberta. The thousands of 2x2 cedar pegs were put in with a jackhammer. The wood started out as lifts of 2x4 that was ripped in half cut to length and pointed. The many bags of sawdust were worked into our clay garden spot,,, awesome soil sterilant! Nothing grew there for years! I am told poplar decomposes quickest and has the least ph altering.
sawdust.
I am by no means an expert, but I did study forest soils as a graduate thesis in college in the ancient times. Here is the deal. It is like Ron said. With the addition of a fresh source of organic matter very high in carbon, the microbes in the soil use the natural nitrogen in the soil to break down the nitrogen-poor organic matter. They require nitrogen to breakdown the new organic matter. While that is happening, the natural nitrogen in the soil is tied up by the microbes, so the plants growing there become nitrogen deficient (they cannot get it because the microbes have it). Without adding supplemental nitrogen to fuel the microbes, plants will suffer a temporary shortage of nitrogen. After a while, it all comes back into balance since the soil cannot "store" nitrogen. Excess nitrogen is leached from the soil by normal moisture movement through the soil. In the meantime, the plants suffer becaues the microbes are using the available nitrogen to break down the sawdust. Most manure is rich in additional nitrogen, so that is not a problem. Wood however, for example sawdust, is low in nitrogen, so wood is a good soil amendment only if it has already had time to be broken down by the microbes as in compost. Woody debris needs to be composted before adding it to the soil so the microbes can have their way with it without robbing the soil of the nitrogen that the plants need.
Have used sawdust for years to break up heavy clay soil in the garden. Usually added 10-10-20 to make sure I didn't come up short on nitrogen. In my current garden I put in 10 yards of old sawdust that had been composted for 30 plus years. And use fresh sawdust on the blueberries every Spring.
Know a fellow growing rodies in nothing but wester red ceder sawdust from a shake mill. Has 3,000 to 5,000 of them and they do great. Says he uses almost no other fertilizer. Also tills it in his garden, but does it in the Fall, lets it break down over the Winter. Have always read that there was an oil in WRC that prevented growth but he says it just prevents germination when it's fresh.
Wow a landscaping question on the FF, WuHoo! 8)
The effect is going to vary a good deal depending on the sawdust type and the amount of bark or other materials in it. Sawdust can run from mildly alkaline to highly acidic depending on species, and it composts slowly with limited nutrient return save a good potashe boost for flower production.
Rhodies are acid loving plants and cedar is one of the sawdusts that will lower the Ph of the soil so he's making his Rhodies very happy. :) I've had tulips get burned and drop all their flowers in a under an hour from finely shredded pine bark mulch which is also acidic, doesn't make for happy customers. :(
Clay is very rich in nutrients so cutting it with sawdust has a positive impact on the nutrient levels through the beneficial effect of maintaining water retention while opening the soil for root growth. Cutting a sandy soil with sawdust only benefits weeds (and a few oddballs like Lupine) which need less nutrient to thrive. Placed on top of the soil as a mulch usually works out fairly well as the bacteria only interact with the bottom of the layer where the moisture levels stay higher. Compost or mild fertilizer can always be added around the dripline of plants to offset any temporary reduction existing nitrogen.
Like it has been said to compost anything you need the carbon material (provides the minerals) and the nitrogen rich material (to provide the food for the microbes), oxygen and moisture. The microbes eat the nitrogen rich material which produces heat as the the little critters multiply and this process breaks down the carbon rich material. Usually when composting you use something like dead leaves for the carbon rich material. Wood and sawdust are EXTREMEY high in carbon and requires a huge amount of nitrogen rich material to compost correctly. Usually you want a 10:1 carbon to nitrogen ration when composting. This can equate to about a 3:1 ratio by bulk when you are talking leaves to other nitrogen rich materials (like food scraps or grass clippings). With wood or sawdust it would be like a handfull of sawdust to about 10 gallons of nitrogen rich material. Even then you cant get the nitrogen rich material to get in contact with the carbon rich material and you will get a very stinky sloppy mess.
Everything I have read and studied is that if you want to compost sawdust, do it in a seperate pile and add a nitrogen rich suppliement such as urea. Even then you need to turn the pile to allow a good mixture of the materials and also allow oxygen to get to the center of the pile or the little microbes will die.
If you mix sawdust into the ground it will use all the availble nitrogen in the the soil and you won't be able to grow anything until the sawdust finishes it's composting process and returns the nitrogen to the soil.
With that said, sawdust can make a great mulch. The minimal ground contact won't depleat the soil of it's nitrogen and it will over time compost down. Don't get the sawdust too thick if you are usining it around plants or it will simply block moisture from getting to the ground. And never mix the sawdust into the ground unless it has been composted seperately first.
I've been composting for years and have done a lot of research and made the mistake of using the sawdust from milling an oak as mulch. I scrapped as much as I could off the gardent he next spring, but I couldn't get all of it off and the garden was amost barren for 2 years even with significant soil ammendments.
Tim
Interesting, with the manure composting, it takes about 5 years to compost the shavings and chips if undisturbed in 3 foot deep piles. There is nearly no smell but the piles do produce lots of heat, they will be steaming in the middle of winter if you dig into one.
If you turn your "working" piles regularly, you can compost in a few months. If you don't turn them, the heat in the center sterilizes the pile and you lose your bacteria.
Once a pile begins "working" you use it to innoculate other piles, or just mix new material into the working pile.
Quote from: tim1234 on February 27, 2007, 08:01:25 PM
With that said, sawdust can make a great mulch. The minimal ground contact won't depleat the soil of it's nitrogen and it will over time compost down. Don't get the sawdust too thick if you are using it around plants or it will simply block moisture from getting to the ground. And never mix the sawdust into the ground unless it has been composted seperately first.
I've used this method as well, and it works great for keeping the weeds away. The first time I used this method, however, I had it too thick, like Tim mentioned, and the sawdust became crusty and hard on the surface, preventing moisture. I find a thinner layer, reapplied once or twice during the summer is the trick.
I've got a huge pile of sawdust and shavings, must be 10 feet high and 15-20 feet in diameter (well it's huge to me!) ;) and I have been talking to the horse farm people up the road about getting a spreader full of horse poo once a week or two weeks to mix with the sawdust. My boys are building a composting system as part of a Boy Scout merit badge and we intend to have yards of the "good stuff" for gardening. Also plan on raising chickens this summer and also planting a bunch of blueberries, so I have everything I need. Definitely have to compost it first before mixing with soil.
Last year I buried a pile of snow under my sawdust and shavings and there was still an ice ball in there the week after July 4th.
Why not send the sawdust up to those horse people, and bring it back already mixed? I'm sure they would be more than happy to accommodate you. ;)
We have never had problems getting rid of sawdust. We sell it by the trailerload and have customers all year long. You might even be able to sell them the sawdust.
I don't really have an ongoing supply. Maybe a cubic yard a week, or less. Basically planer shavings right now. They have their own source, and they are always looking for a place to get rid of horse manure.
I'll take some!
I can't finalize the deal on the horse manure down here, i've found a few sources, but can't get them to continue enough conversation for me to get some!
are leaves high in nitrogen?
Dan my friend,
You are not far from the world's largest concentration of bull$hit on the entire planet - you should be able to get plenty of it! :D ;D
Dan_Shade I'll cover you on this one...
Engineer - there's a difference between bull6!@#%^&* smiley_bull_stomp and useless bull6!@#%^&*. smiley_smelly_skunk
BTW Dan green leaves are high in nitrogen but dry leaves are not much better than sawdust.
ok, that's what I figured, I have lots of dried leaves, and lots of sawdust!
you're right, between DC, annapolis, and baltimore..... no wonder the chesapeake bay is so polluted!
Remember, most of the good stuff in Compost comes from the minerals stored in the leaves used for the carbon material. Trees roots reach way down into the ground and pull up lots of great stuff. All those minerals get stored in the leaves and are released back to the top soil when the leaves naturally compost down in the forest. Composting for your garden is just an imitation of nature. There really isn't that much mineral content in wood including sawdust. If you compost with sawdust you will get a inferior compost compared to composting with leaves (sorry guys). The compost will improve soil texture, but won't bring a lot of nutirents which is on of the main reasons people compost.
Most of the time manure is already mixed with straw from the animals stalls and is already a premixed compost pile from the get go. Mixing in more carbon will just slow the process.
I doubt you can compost down sawdust in a single season. If you do use the mixuture before it has completely composted down you will get into the same issue I mentioned in my previous post - a barren garden. But if you have the sawdust and a lot of time, go for it!!!
Tim
While I know it's not the best thing, having something to do with the sawdust is all I'm really looking for. I certainly don't want to bag it and put it into the landfill.... i'm sure i'm not alone.
i keep meaning to start trying to collect the coffee grounds at work, but I never think of it at the right time.
Put a drywall bucket with a 13 gallon trash bag as a liner next to the coffe pot. Then put up a sign asking people to put the grounds in the bucket. they catch on after a while. I would get 15 gallons of grounds a week. Coffee is a great source of nitrogen and if you have enough of it, because it is ground up small would be a great addition to a sawdust pile. You just need a pile of coffee grounds the size of your sawdust pile!!!
Tim
that's my master plan, but it will have to look better than a bucket where I work, it will have to be some fancy setup.
Paint the bucket. :D
Where do you work?
I was working at Ford and they didn't complain about the bucket and trash bag one bit.
Tim