Do woodchips acidify soil?

I often hear that one should not put on too much woodchips, as they acidify soil.

I wonder if this is true - we use a lot of all kinds of ramial wood chips and the plants are doing great. We don't turn them under.

Can anybody tell me which research this statement is based on?

Hi Susan.

It depends on the type of wood chips. What they will actually do in quantity is raise the potassium levels.

Wood chips are going to take longer to decompose than, say, sawdust, which has a much greater surface area for the same amount. Also, whatever effect they have on your specific soil, it will happen faster if you mix them into the top layer of soil. If you have any concerns, just leave them on top of the soil.

Another thing you want to consider is that woodchips properly inoculated with fungi will be beneficial to your soil conditions, as the fungi will create networks under the soil surface to move things around to where they're needed. This will take care of, for instance, that eventual potassium buildup I mentioned.

Have you gotten a soil test done? If not, I would suggest that. Even if you're working with a tree whose chips will acidify the soil to some extent, maybe your soil needs it. You won't know unless you test your soil.

Good luck, and keep us posted.

-CK

Hey Susan-

I'd like to further what Chris mentioned that it is the kind of wood that can have an acidifying affect on soil. For example, pine wood chips can an acidifying affect. You mentioned you're using ramial wood chips, and that you're plants are doing great, so I personally wouldn't be worried about those wood chips acidifying your soil. I myself would just keep doing what you've been doing. Hope this helps!

Susan Wakeman wrote:I often hear that one should not put on too much woodchips, as they acidify soil.

I wonder if this is true - we use a lot of all kinds of ramial wood chips and the plants are doing great. We don't turn them under.

Can anybody tell me which research this statement is based on?

As Chris and James have mentioned, the type of wood chips make the difference in acidification.
Pines are going to acidify soil more than Red cedar and juniper tree wood.

This acidification isn't going to be instant either, it will take time and then there is the wood dryness effect on the acidification, green pine/ true cedar/ juniper will acidify more than 2 year dead wood.
In the pinus and juniperus species there aren't many fungi that act on freshly downed trees, the fungi normally don't become active until the wood has dried down.

Oak, Hickory and most of the other species of deciduous trees are not going to acidify the soil but they will add more potassium, they also will carry more, different varieties of fungi spores and that is a good thing as  Chris mentioned.

The Statement of wood chip acidification most likely comes from some lay-person who thinks that wood chips have a greater or faster effect than they really do.
There is a paper, written by three Chinese researchers on acidification of soil by pine tree species, but they were looking at living trees and the soils around them. (pine trees like acidic soil and they can exude chemicals to acidify the soil so they have better living conditions, pinus are bacterial trees instead of fungal trees).

Redhawk

Short Answer is NO woodchip does not acidify your soil

I have heard people say that drinking apple cider vinegar with a pH of 2.4 as alkalizing which I find to be confusing.
I will say that raminal woodchip have a pH very close to 6.8 and even dry regular woodchip have a pH close to 7.

I will say that if you bury woodchip it will create an explosion of fungi soil life, and they will out-compete the plant roots and "stunt" the plant.
To avoid this "over-population" of fungi and plant "stunting" don't bury the woodchip only lay it on top of the soil as in regular mulching.

Pine Needles like Lemons do have a pH of 3.
So if you were to blend either one up the liquid would have a low pH.
However if you just leave them to dry out, acids like the water will evaporate and the drymass will have a pH of 7.
The acids are also water soluble and really just gets washed away or deconstructed after they react with the soil.

S Bengi wrote:
I will say that if you bury woodchip it will create an explosion of fungi soil life, and they will out-compete the plant roots and "stunt" the plant.
To avoid this "over-population" of fungi and plant "stunting" don't bury the woodchip only lay it on top of the soil as in regular mulching.

Sorry but I have to call bunk on this statement.

Fungi that would come from buried wood chips will be a boon to the soil and the plant roots not a detriment.
Also the spores would need to bloom before the hyphae could even start to develop and that takes near perfect conditions to become an "explosion" plus these spores would first decay the wood chip they were on and since spores land on exposed surfaces if the tree was cut and chipped with the wood chips going right where they were going to end up, there would be little chance for every chip to contain spores.
In no research has it ever been proven that hyphae do anything to plant or tree roots that could remotely be called "Stunting".
Fungal hyphae are either mycorrhizal or they are connectors (mushroom producing) to those mycorrhizal fungal hyphae.
Fungi tend to help create structures in soil that helps the soil hold more moisture so that isn't an issue for any root system either.
Fungi also are known predators of detrimental nematodes thus being beneficial to root systems from all aspects.

Redhawk

In reaction to S Bengi and Bryan RedHawk,
Burying woodchips DO stunt plant roots when you plant directly in the woodchip layer, NOT because of the fungi but because of microorganisms that breaks the woodchips down. Micro-organisms use up a lot of nitrogen in the process of decomposing the woodchips, which they take away from the soil around them. When you put plant roots directly in this part of the soil containing the woodchips there might be a temporary nitrogen deficiency. Plants need nitrogen to be able to grow, thus this can lead to 'stunting' a plant.

I am in agreement with RedHawk on this one.

This last summer I planted tomatoes is pure wood chips that were partially decomposed by Wine Cap mushrooms.  And by pure, I mean the bed was about 10-12" deep, filled entirely with chipped up wood before reaching any soil.  I simply scooped away about 6" of chips, dropped the tomatoes right in the holes and covered up.  Then I stood back and watched them grow up into lush, dark green tomato plants with plenty of fruits per plant.  Again, I added nothing to the wood chips, but they were about 1 year old, partially decayed but still obviously wood chips.  Nothing about those wood chips stunted the tomatoes in any way whatsoever.

Eric

I saw on Youtube a girl who has planted her sweet potatoes straight into a pile of wood chips.
She said that she had great results.
As I had a pile of more or less sawdust with a few small bits of wood in it from a mulberry tree
and not much earth or compost otherwise, I decided to follow her example. I planted some sweet potatoes in this sawdust. They are doing ok but not growing much as far as the leaves go.

In my place there are a lot of 'green' oaks (that's what we call them in french), maybe called holm oak in English? And there are also a lot of chestnut trees. Wood and leaves from both these trees are supposed to make the soil acidic because they have a lot of tannin. So I never use their leaves for mulch or in the compost.
But I thought that wood from the mulberry tree would be a different story as mulberry trees also bring up a lot of miinerals from deeper layers in the soil.
We will see how it goes!
IT is an interesting added source of fertility. Where I live we saw wood to burn in the winter for heat so there is always sawdust which I considered an irritating waste product. Now all of a sudden it has become an exciting source of (possible) abundance!

I am glad that this thread got bumped up.


I will state again that woodchips are not going to damage your soil.  To the contrary, woodchips will do wonders for garden soil if you let them.

It has been five years since I last posted on this thread and since that last time, I have had a sort of revolution with woodchips in my garden.  By now, I don’t even think about starting a garden bed unless I can pile a bunch (6-12 inches) on the surface first.  I no longer till the soil beneath, but I might lay down a compostable weed barrier to eliminate any weeds before they start.

In the meantime, the woodchips will rapidly break down (the cardboard layer won’t last long either), microbes from the soil will work their way in and earthworms will start to drag down bits and pieces of specs of debris or partially rotted wood.  By the end of the growing season, it becomes hard to discern where the woodchips end and the soil begins.  The two layers just merge together.

And the resulting bedding is amazingly fertile.  It teams with life!  Nutrients from the soil are dragged up to the woodchip layer.  The decomposing woodchips absorb and hold onto water like a sponge.  Microbes fix nitrogen from the air (want to boost this effect—plant legumes right into the chips!!).  And this bedding only gets better with time as long as it doesn’t get abused and gets just a little bit of TLC from time to time.

I am in the process of creating a new garden plot and I am acquiring trimmed brush that I can chip up as a primary resource for the new bedding material.  I will blow the chips right onto the beds and I will further accelerate this process by inoculating the chips with mushrooms.  I fully expect a very fertile bed very soon!!



Eric

Sat Atma Khalsa wrote:I saw on Youtube a girl who has planted her sweet potatoes straight into a pile of wood chips.
She said that she had great results.
As I had a pile of more or less sawdust with a few small bits of wood in it from a mulberry tree
and not much earth or compost otherwise, I decided to follow her example. I planted some sweet potatoes in this sawdust. They are doing ok but not growing much as far as the leaves go.

What kind of wood chips was she using?  And what kind of sawdust did you use?  

Maybe sweet potatoes prefer the kind of wood her wood chips were from.  And maybe the sweet potatoes from your sawdust did not like that kind of sawdust.

The great question is was the wood chips alkaline or acidic?  Same with the sawdust?

I agree with Eric that wood chips are great for soil.  

Did the girl plant directly into wood chips with good soil below?  Did you plants the sweet potatoes directly into sawdust with no soil?

Washington State professor Linda Chalke-Scott, of “Horticultural Myths”, stated on the Orchard People podcast that “no mulch will change the pH of soil”. I do not agree with everything she asserts, but I like her challenging of popular opinions. Her reasoning seemed to be that any reasonable amount of mulch’s volume and mass is going to be insufficient to change the pH of the mass of Earth we are working with.

https://puyallup.wsu.edu/lcs/

In my research of coniferous forests with acidic soil, it is the root exudates and climatic factors that make their soils acidic. I have not had pH problems mulching extensively with conifer chips, but do avoid pulling from piles with more than 10% highly tannic redwood or cedar. I have also conducted dozens of water tests in creeks running through old growth conifer forests with soil in the 3s to 4s pH, and the creeks running out of them were in the 7-8.6 range.

Sat Atma Khalsa wrote:I saw on Youtube a girl who has planted her sweet potatoes straight into a pile of wood chips.
She said that she had great results.
As I had a pile of more or less sawdust with a few small bits of wood in it from a mulberry tree
and not much earth or compost otherwise, I decided to follow her example. I planted some sweet potatoes in this sawdust. They are doing ok but not growing much as far as the leaves
But I thought that wood from the mulberry tree would be a different story as mulberry trees also bring up a lot of miinerals from deeper layers in the soil.
We will see how it goes

Sawdust is not going to act like wood chips. Sawdust is so fine that it will compact and thus not allow water or air to reach the root system well enough to produce tubers. Wood chips work because the structure is open for air and water to infiltrate easily, which allows for tuber growth.
Redhawk

I had 2 dump truck loads of wood chips dropped on the back edge of my property a few years ago.  The piles were enormous.   They had been freshly cut and it was awesome to see the steam rising from them in the fall as they began to decompose.  

I used them to mulch a 100 ft rectangle of vegetable garden as well as other paths and garden beds.  Still had a lot.  Over two-3 years they broke down; and now mixed with clay soil make the greatest dirt.  

I actually planted directly in them the spring after they were dumped in the fall, by spreading out cardboard, a thick layer of mulch, and then planted vining squash, cantaloupe and watermelon.  They did great.  The wood chips did nothing to the soil except keep it moist.