Wood chip garden mulch comparison

I tried using a thin layer of wood chip mulch on the surface of one of my garden beds this year as a trial. Having read a lot about the back to eden method, etc. Everything else was the same - same amendments added, compost, watering routine, etc.

These two beds were planted the same day. Slightly different mix of plants but each had two beet varieties that can be seen clearly in the pictures. The difference in growth of the two beds is dramatic…


The conclusions is wood chip slowdown the growing of veggies.

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Unless you compensate the temporary bacterial orgy of sucking N out of the soil to help digest the carbohydrate in the wood. I want to see what happens if you give those vegies in the wood mulch a significant boost of water soluble N.

I put down a 90 day coated urea before mulching my fruit trees with wood chips. In my veg garden I water with diluted urine and it seems to more than compensate for the shredded wood I often use as mulch for my vegies.


i mulch all my raised beds a hell of a lot more than that and have had 0 issues with lack of growth. actually to the contrary. more mulch the less they dry out the more they grow. as long as you don’t turn the mulch into the soil the N in the soil isn’t affected. been doing this over 6 yrs. now. usually put down at least 2in. of fresh wood chips after planting. they sprout right though the mulch.


I have read many times on various forums and articles that as long as the wood chips stay on the surface, nitrogen robbing isn’t an issue. I wanted to test that theory and I believe based on this trial that theory is not correct.

With respect to adding soluble nitrogen to help boost the plants in that bed - I wanted to maintain identical conditions between the beds, and so use the same amendments, to isolate the effect of the wood chips. Furthermore, I actually DID use a few soluble nitrogen applications on both beds. The wood chip bed was still stunted.

Now, this is just one trial. There could be confounding variables that I am not aware of. I got the chips from a local tree service. Perhaps the wood chips contained an allelopathic species. Perhaps there was herbicide contamination. Maybe something else happened.

This post was just a FWIW data point / anecdote to add to our body of knowledge…


Moose we wrote our posts simultaneously and my post was not directed at you.

That is very helpful first hand knowledge.

Again I am just providing one data point…


like you said, maybe there was some walnut in the mulch. none here so it isn’t a issue. only thing i won’t use here is cedar. but if its a few years old its ok. in fall i turn the mulch into the bed. by next spring its all decomposed. i also don’t add any extra N but will occasionally use some miracle grow to give them a boost mid summer. maybe this makes up for it?

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Do you let your chips age or compost them prior to using?

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no. i use fresh chips made the day i get it. it does contain the leaves and needles mixed into the chips so that would help it break down quicker id think.

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i also use fresh chic manure bedding to fertilize my trees and bushes the spring, then cover with fresh wood chips. breaks down very fast. by next spring theres barely any left.

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It’s hard to believe a thin layer on the surface like that would have a dramatic effect one way or another.

My container garden consists of nothing but wood chips decomposed over about a year with urea commercial fertilizer, spiked with trace elements based on soil tests using real chemical name ferts.

The plants grow strongly if I get the proportions right. I’ll add 50 grams of urea a week to a 1.3 cubic yard pile to keep the N up. These things are tremendous and perhaps more importantly, long term, Nitrogen sinks. “ Finished “ compost is an opinion more than a verifiable fact.

In my cool climate I’ve felt that a deep mulch applied early inhibits soil warm up and growth that way. The thin layer you show doesn’t look like it would hurt that way.

I’ve tried to compensate by adding extra N for chips buried in the soil before they have properly decomposed, without much success. Too much of a moving target.

I suspect an extraneous confounding factor. Did you burn them with hot chicken manure maybe? Chicken manure is about as sure-fire as it gets otherwise.

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I perma garden with wood chips and leaves. I just pull back the refuse and sow or plant plants. Every year they do better and better. Also grapes and fruit trees are mulched with wood chips and need no additional fertilizer.


So you are basically using compost with added urea. To be clear, I used freshly chipped uncomposted wood chips.

I used the same fertilizer routine on all the beds. Topped up bed with compost, added bonemeal, feather meal, lime - allowed to rest for several weeks prior to planting, then periodic dilute soluble urea applications.

Also Koko - 50 grams a week for a year is almost 6 pounds of urea fertilizer. Do I have that math right? That’s a very healthy dose of nitrogen.

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I have often encountered what appeared to be alleopathic consequences from fresh chips. I always use wood mulch that has received lots of rain and been aged for half of a year when it is to be used for young vegetables. There isn’t adequate information about trees containing alleopathic compounds but I’m pretty sure cedar should be on the list along with black walnut, but probably a lot of other species have this power as well.

Whether or not plants are effected by lack of nitrogen depends on the location of their roots. If conditions are particularly wet, whether due to soil texture of continuous rain, roots will be much more oriented towards the soil surface. Young vegetable plants will have roots closer to the surface than established ones, also.

The process of decomposition is also possibly acidifying at the soil-mulch interface where most N. depletion also occurs.

All that said, perhaps soil temps are the most important issue, and wood mulch can slow the rise of soil temps in spring to allow adequate access to P along with other root growing activity that requires warmer soils. Once summer temps occur the cooling affect of mulch during the day is welcome as is its ability to hold warmth in the soil at night.

Carbohydrate rich material on the surface also encourages available N in fertilizer to volatilize into the atmosphere, so it is best watered in immediately and not allowed to sit on the surface against mulch.


Oh yeah, although I skip for months at a time during the coldest months. Remember , when I say 1.3 yards, that’s 100% “browns”as they say.

As I said, the stuff is a tremendous N sink over time, not just the immediate composting process. There’s a reason why they use it for privies. My addition is about equivalent to two or two and a half gallons of animal urine a week. A piece of cake for a pile that size.

That said, when I use it for top dressing older containers, it obviously leaches down. Never saw any sign of upward wicking of nutrients. The stuff is largely depleted at the end of the season based on soil tests.

I’m at a loss for the described action, unless the material was put on thicker than it appears in a cool climate and the soil didn’t warm up, or the material was contaminated one way or another.


I’m with hillbillyhort & kokopelli… have a hard time thinking that minimal amount of woodchips is the issue… I was looking at the photos, going… OK, where is the woodchip mulch? I thought that was just left-over from last year’s endeavors. When I put it on, I put it ON!


Related to orchards…a paper…

Some previous studies showed substantial benefits in tree growth, nutrition, yield, and soil conditions under orchard mulch systems and the advantages of mulches often are as- serted in popular gardening magazines. However, because most mulches are more expensive to establish and main- tain than herbicides, it is important to determine if the benefits of mulches compensate for their additional ex- penses. Our economic studies indicate that, for some fruit varieties, the in- creased crop value in mulched trees probably justifies the greater costs. Conversely, reduced fruit quality and lower packout crop values for trees in some herbicide systems may nullify the cost savings of these GMSs. The an- ticipated long-term benefits of in- creased soil fertility under mulches certainly are of some value, but were uncertain and inconsistent after 4 years in our field tests.”

As for my garden, recently planted and mulched with 1” of woodchips. I can attest to the water retention. My soil is beyond sandy and dries out exceedingly quickly in sun/wind. A few hours of sunlight make walking barefoot in the garden really painful… soil too hot to touch! With the chips, water stays in the sand/soil, even at the interface of soil/mulch, weeds are suppressed, and the soil remains a reasonable temperature.

My orchard rows have 4-6” of chips. Digging in, there is plenty of mycorrhiza, moisture, and weed suppression. Joy!

In my last expansion of the orchard, I tilled new land and had two rounds of cover crops. Both had buckwheat. Round one, growth of 6-12 inches in many places. Before tilling it in, I spread woodchips maybe 1-2” deep and replanted. The size and health of the second round of buckwheat was dramatic… 24”+ plants were the norm. I knew the risks of potential N lock, but it would be short term, at worst, and would add a lot of organic material to the soil beyond the first season or so. Now, the rows are mulched deeply, grafted trees are in, and I’m going to continue use spreading/tilling in chips in the alleys.


I was told straw is good for raised beds as a mulch to help keep the moisture, to keep weeds out and once it breaks down it adds organisms to the soil.
I went and bought some and used on my raised beds this year since is my first year doing raised beds but the straw bail that I purchased come with lots of seeds! Now I have to pull straw and weds. :rage:

Someone else mentioned that grass clippings are the best thing to use for raised beds as a mulch. But you have to make sure there’s no seeds in the clippings otherwise you’ll be having the same problem that I’m having now.

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Alan - can you share a brand name of the coated urea?

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