concerns with using cardboard/newspaper as a mulch

paul wheaton wrote:
Another problem is that newspaper/cardboard tends to not break down particularly fast.   And  since the mission is usually to smother something that is already there, it is placed in sheets.  If too thick, it could make a layer that cannot be penetrated by water or air - maybe for many years. 

I've never had issues with cardboard or newspaper breaking down properly.

paul wheaton wrote: Last spring I visited somebody's garden where an apple tree was doing poorly.  After digging around a little, a layer of newspaper was found about an inch under the soil.  It was about a quarter of an inch thick and had apparently been put down to kill weeds about five years earlier.  It killed the weeds.  And it was making the tree sick.  And it wasn't breaking down.

Seems like a post hoc fallacy to me. Further testing would be required to see if it would in fact damage the tree. I've also never had this issue, but I have seen apple trees dying due to poor soil drainage in heavy soils. This could be the problem, not the newpaper, which would explain why the newpaper didn't break down; no microbes where available to do so. Once again TESTING IS REQUIRED. Our speculations have no scientific merit.

Leah Sattler wrote:I prefer hay for alot of reasons. for me most of it is just practical.

Same here.
We love hay and use bailed green alfalfa. It smells so sweet when you spread it. It builds up successively decayed layers and makes the soil spongy.
Everything combustible goes into the wood stoves to start fires. Then the ash goes into the poo composters and the garden.

I placed cardboard down under about 6" of mulch in the front yard about 2 years ago. We got very little rain, just under 3" in the first 18 months, and the cardboard was still looking new for over a year. In the last 6 months we've had about 17" of rain, almost twice as much as normal, and the cardboard has mostly dissolved as a result with lots of happy worms underneath.

I did discover that the cardboard boxes I used had a fine plastic mesh built in so as I was digging holes for new plants, I was hitting this mesh with every scoop. So I would suggest testing any cardboard you use first, tear each box a bit and if it's too tough to tear, there's probably some unwanted extras hidden in the layers.

Kabir424 Hatfield wrote:I live in Alabama and I have used cardboard on a couple of different occasions to kill off grass and add carbon to the soil. I usually just lay out cardboard from boxes with all of the metal and plastic off and then top that with leaves, compost, grass clippings, etc. This has happened on 2 separate occasions when I start this in the early fall and then by early spring I can dig these areas up to mix in the organic matter. The cardboard is still recognizable as cardboard but it is easy to rip to pieces and include into the soil. One year later I haven't found any pieces of cardboard in the soil because it has all broken down. I don't know if this is because I live in Alabama and we have such a long time period for things to break down or if its because I have overly active soil buddies or if it is something else. But, I haven't really had a problem with 1 layer of cardboard breaking down within a year and a half. This doesn't address any issues of toxicity leaching from the cardboard if there are any.

I think how "brittle" the climate is might definitely make a difference as far as whether the mulch breaks down quickly or might become a stifling layer. We've used sheet mulching (usually cardboard with woodchips or straw on top) at pretty much every farm I've worked at -- around the Great Lakes, upstate NY, north-central CA, and southeastern U.S., and never had a problem with it not breaking down. In one garden, we would sheet mulch probably a half acre with newspaper, three sheets thick covered with hay from our fields, and cut holes into each seedling when transplanting. It seems an incredible tool for establishing a new area, especially with a lot of more perennial weeds and/or woody stumps and residue, as well as around perennials, especially those with roots close to the soil surface, where weed control can be pretty tricky. When removed, generally reveals rich dark soil and awesome fungal activity. The one occasion where I saw it fail miserably was at a garden in Santa Fe. NM. In this harsh dry climate, it just sat there and fossilized -- we were still finding chunks of cardboard and dessicated horse manure in beds they had initially tried to prepare through sheet mulching four years earlier.

The question of toxins is an interesting one to consider, I have never observed anything that suggested to me that it hurt the crops around it, but if there are substances that damage the soil ecosystem, or can be absorbed by the crops and then us, that would give me pause. Any other alternatives beyond just straw or hay? In my experience, I haven't found these to be nearly as effective at suppressing weeds (and indeed can contain plenty of weed seeds themselves), and we are always scrounging for every last bit of carbonaceous mulching material we can scrounge up for the trees, garden, and composting toilet as it is, certainly not enough to cover everything in a thick enough layer of mulch to suppress weeds, especially perennials. Meanwhile cardboard and newspaper can be diverted from the waste stream into a free, effective resource and tool. Definitely a lot of gross chemicals involved in paper products, I would be interested to learn more how much of a concern they truly are in a garden.

It seems like the perfect tool though...trash used in a variety of handy ways. However, the issues with paper/cardboard items and chemicals are real and complicated. This link should be enough of a starting point to go down the rabbit hole:

https://www.paperonweb.com/chemical.htm

So it isn't simply glues and absolutely not just wood pulp. The FDA in the US addressed 3 chems in wide use for things like pizza boxes. That only scratches the surface. Look on the bottom of a LOT of produce boxes. Many contain warnings regarding reuse. I agree with someone way back on this thread that cardboard shouldn't need these things.

We all make our own decisions of acceptability but I'm expending far too much effort and time to build long-term resources here to not consider the precautionary principle. I don't use paper in the compost. Usually what does come onto property as a result of shipping and/or transport leaves just as quickly. Almost anything could be used for something else or in new ways. I guess I'm trying to say I try not to let "can be doing" override "should be doing". I'm already dealing with decades of coal burning and don't feel like I need to be trading current legacy issues for future potential ones. YMMV.

The mechanical pulps are primarily used in newspaper and magazine paper and the chemimechanical pulps for cardboard and soft paper.

--wikipedia

I was trying to find a way to determine which kind of processing from the feel 9f the cardboard, but it doesn't seem likely.  And there have been multiple mentions of newspaper causing problems on this thread.  Hm.

paul wheaton wrote: I understand that in the permaculture world I am in the minority on this one.  Most permaculture folks are not concerned (including Sepp Holzer, Bill Mollison and Paul Stamets).

I've often wondered why they aren't more concerned. I've even asked an organic farmer who felt it was okay. I might use it for landscaping but not in a food garden.

A timely revival of this thread!

It is probably worth bringing up that the widespread finding of PFAS in toilet paper is likely the canary in the coal mine indicating that the recycled paper pulp stream is heavily contaminated. Paper-based food packaging often contains PFAS to prevent grease and liquids seeping through -- when these items enter the paper pulp stream, they are adding to the base load.

The litany of potential negative health effects from consuming PFAS is considerable, and this could be a reason to stop using cardboard in the garden -- particularly pizza boxes, but possibly other types as well.

I do personally use cardboard even so, but as a single application to suppress some of the extremely aggressive grasses we have here while establishing garden paths (not in the main garden beds themselves). I also make sure to never use color-printed cardboard, as the inks are still soy-based, but the pigments often contain lead (white, red, green), mercury (red), cadmium (red, yellow) and copper (blue, green) -- only black ink is relatively safe. Given that cardboard is a recycled material, it will have some quantity of these heavy metals from its recycled post-consumer portion. Use with caution!

I totally agree that cardboard, and newspapers are not a really great mulch. Not only there is glue and other icky stuff in there, nowadays, there are also PFAS in some of these water resistant products. I will keep asking for a complete BAN on PFAS.

I'm a bit suspicious of cardboard because I did a couple of years in a big box distribution center. The chemical smells that came out of some of those tailors, having just arrived from China, was often to put it mildly, a bit off-putting. Not to mention the chemicals used in case something alive was discovered on opening and it was sealed back up and fumigated.

Even though some, maybe most of it is probably fine, the amount I allow in my garden is, none.

If you have stopped using cardboard, have you found something that works as sheet mulch? I’ve been using it to smother grass.

This article just came out.

cardboard-does-not-belong-on-your-soil-period/

May Lotito wrote:This article just came out.

cardboard-does-not-belong-on-your-soil-period/

Thanks, May. This article is indeed extremely informative and I noted especially the inset table about PFAS and PFOAS and other bad stuff I've never heard of. I was planning to suppress weeds before installing some winecap mushrooms a a couple of beds this spring. I won't be using cardboard, that's for sure. I think I'm back to the conventional weeding for them.
I have become very interested in these "forever chemicals" since studying water in our County. Right now, our legislators are debating... and debating... and debating how to best remedy the soil once it is contaminated. The best analogy I can think of is that they are like unruly kids in a flooded house arguing about who is going to grab the mop, and I'm yelling: "FIRST, TURN OFF THE WATER, YOU IDIOTS!".
All these chemicals should be banned, period, full stop. There is so much convenience and money in continuing to use them that it will be extremely difficult to put a stop to them, but we must try. Presently, we all use items in our everyday life that contain PFAS without knowing. A person has to be extremely savvy to avoid them because since the 1940s, they have been in use and are now ubiquitous. As is, most of us  have some in our bodies:
"PFAS are known as “forever chemicals” because once released into the environment they do not break down and they can build up in the body. The Centers for Disease Control and Prevention has detected PFAS in the blood of 99 percent of Americans, including newborn babies. "
https://www.ewg.org/news-insights/news-release/2023/11/new-epa-data-show-millions-more-have-forever-chemicals-drinking#:~:text=PFAS%20are%20known%20as%20%E2%80%9Cforever,of%20Americans%2C%20including%20newborn%20babies.

Bethany Brown wrote:If you have stopped using cardboard, have you found something that works as sheet mulch? I’ve been using it to smother grass.

I haven't stopped using cardboard/newspaper because I never started using those.

Organic matter placed 6 to 12 inches will smother grass.  12 inches is best.

Some organic matter would be wood chips, leaves, coffee grounds, compost or even soil.

Also discussed here https://permies.com/t/18887/paper-poisoning-permaculture-produce-soil

I very recently gave in briefly and used some cardboard and feed sacks in one small area for bermuda grass and never felt good about it...after decades of not using cardboard and paper in our gardens I  look at that area as contaminated

We mostly try to keep things growing everywhere or covered in a mulch.

I have been getting burlap bags from a local coffee roaster and will put those down and cover with woodchips, etc.  Still lets water and gases through, fewer potential contaminants but still only use for non-edible areas where I am doing habitat restoration, meadows, etc.  Not available everywhere but one could look for other sources of 'waste' fabric.  

What about tree bark?

It is Nature’s “cardboard”, normally a waste product, and it is easy to pry off of any spring-cut wood. Or from partly rotten wood. However it could be equally or more valuable as roofing.

Old thatch may also work well as it is tightly bound but you have to have that around, first.

The way the forests do it, is by dropping whole trees down.

A 6-in or thicker layer of sawdust is what I have used most often.

How did people deal with this 200 years ago, or even more recently?  No plastic tarps, no cardboard.

Kevin Feinstein II wrote:How did people deal with this 200 years ago, or even more recently?  No plastic tarps, no cardboard.

Manual cultivation.
It tends to be a lot of work, but people did not have as many choices about how to make a living as they do now.
There were also animal helpers like the cotton patch goose:
https://en.wikipedia.org/wiki/Cotton_Patch_goose