Cardboard mulch after 1 year

I wanted to let everyone know my experience with cardboard mulch after 1 year on the ground. I had put out the cardboard to kill grass and weeds and prepare an area for planting this fall with cover crops.

I covered a bit over 100 square feet with a thick layer of box cardboard. It did a good job of killing everything underneath, but that is all it did. Unlike a mulch of leaves or straw, I saw no improvement in the soil condition. With leaves, straw, or wood chips there is usually an improvement in the soil richness and crumb structure. I saw none of that with straight cardboard. All it did was kill the grass. The only organisms working to breakdown the cardboard were termites.

I had a couple of small areas where I laid straw on top of the cardboard. These areas appeared to be completely decomposed, probably due to more termite activity because the straw held moisture in that area for a longer period of time.

I would have to say that if you are looking to improve the soil, then cardboard is not the way to go. Almost any other mulch would perform better to improve the soil. The cardboard was only good for killing the grass and weeds. I will use what cardboard I have saved for paths throughout my garden.

From my understanding, cardboard or newspaper is simply used to kill off weeds or sod in your case and not to really create compost. You would need to pill other various mulch on top of the cardboard to create nice compost soil and over time the it will work itself further down into your existing soil. I am assuming you were doing the lasagna method.

Kris

I think that the more organic material you piled on that cardboard the faster it would decompose. I have an old hemp shower curtain that I'm going to experiment as a grass suppression layer in a sheet mulch this winter.

Do you have any pictures of the cardboard underneath the straw? How much straw was used exactly?

I tried cardboard once (years and years ago) in a lasagna method, but burried it in several inches of compost. The cardboard did the job of killing the grass and the compost took care of the cardboard over the next few years. It got me to wondering about the chemicals in the cardboard because how long the stuff lasted under that compost... Worked good to kill the grass this way though.

I was always told, and thought based on reading, that the cardboard was only to kill weeds and was used as a layer underneath something that would build up the soil like mulch, compost, etc. Considering how thick cardboard is, and assuming you laid it in sheets, this doesn't surprise me terribly because if it was laid down by itself, it doesn't seem like it would generate enough heat from the layer of cardboard to actually break down and get into the soil by the time the cardboard has disintegrated.

We used cardboard with good results on a hillside. It was full of rocks, poison ivy and other vines. We did not want to dig in it and so for months we tossed cardboard all over it. We used regular cardboard boxes, cereal boxes, cracker boxes, tore up newspaper - basically anything paper we had on hand and we collected paper boxes from other people. We would sit at night and tear up the paper into pieces about the size of two hands. Then, we just tossed it all over the hill. Took a long time but we covered it up. Then, we set logs in place to mark out where we wanted beds, staked the logs in place and piled on more paper in each bed.

Then we piled wood chips in the beds and in some we had horse manure (yes it made a weed mess) and we got some rotten straw too (yes it made a weed mess) and we just kept piling on wood chips and more paper. That was 8 years ago and now the beds are full of good black earth and we do not have much trouble with weeds since we keep piling on paper and wood chips.

Years ago I read Lasagna Gardening by Pat Lanza. It was an exciting book but I never did anything with it.

I now have great concern with this method. Cardboard and paper have glue and ink. When the items break down into the soil, where does the glue and ink go? Into the soil.

I'm going the hugelkulture way. Gonna keep it real.

Good points about the glue and ink. But.....for us it was 7 - 8 years ago and we did not know any better. I would probably still use the newspaper but skip the magazines and cardboard. But, to get rid of the first very bad weeds, then cardboard would be better than using Roundup. Once the initial weeds are under control, then switching to use just wood chips or good rotten straw would work best.

We made another bed using bark and limbs. It worked OK this summer. Still needs to rot some more. Have a good week.

one time I put a double or triple layer of cardboard down and covered it with piles and piles of chopped down weeds..It took a couple years for the cardboard to disintegrate and the quackgrass rhizomes grew right through it.

Classic sheet mulching as taught by Bill Mollison and Geoff Lawton at the Melbourne PDC this week:
1) Area of grass, weeds, soil or whatever
2) Throw on some vegetable scraps or manure, enough to attract worms; doesn't need to be much; this step is optional but recommended.
3) Apply a layer of WELL SOAKED newspaper, cardboard, old carpet or similar. Should be fairly thick - eg 2 layers cardboard or a whole newspaper (the whole thing, not just a sheet). Must be well soaked, to the point of being waterlogged.
4) Apply mulch 1 foot thick; one straw bale will cover 1.3 square meters or 10-12 square feet. Thick mulch.
Planting then proceeds in pockets of compost in the mulch.
There may be pros and cons to the method, but the method is as described above, with too little moisture and too little mulch resulting in dryness and the inability of the layers to become bedding for worms.

But you still run into problems of ink and glue going in the ground. Especially with the old carpet. Lots of glue and toxins there.

I do not recommend these methods.

I tend to figure the ink is likely soy, and the glue is probably gonna be eaten/transformed by soil organisms. I haven't seen anything on cardboard toxicity to make me worry, though I'm open to being convinced.

One other thing: I figure since the worms like it so much, it's probably safe.

You know, like feeding questionable mushrooms to your dog. "Look - he's okay!"

In the North America and Europe, corrugated cardboard box layers are generally glued together with a starch based adhesive.

Corrugated board adhesives

Corrugated board adhesives are the next largest application of non-food starches globally.
Starch glues are mostly based on unmodified native starches, plus some additive such as
borax and caustic soda. Part of the starch is gelatinized to carry the slurry of uncooked
starches and prevent sedimentation.

I don't know what is used in Asia (where a huge % of our products come from). I am guessing that due to cost and availability, they also use starch based glues.

I've used cardboard for weed control in my pumpkin patch for years. I get huge boxes if I can, lay them down like tiles and fasten them with wire staples, then cut holes for my pumpkin, squash, watermelon, tomato seedlings. I lay down paper (plain off-white packing paper, mostly) at all the seams--it goes right on the ground, then the cardboard. I cover the whole thing with straw--this is mostly to make the whole thing look better. The pumpkin patch is a big shallow bowl, so I don't have a big problem with rain running off. I do go around poking little holes in the low spots after I have the cardboard installed, especially if I see a puddle after a rain. I have excellent results in that my fruits are very slow to rot sitting on straw that is over cardboard, and I only get weeds at the edges.

If I'm organized I pull it all off in the fall, or else that happens in the spring. Next step is the cardboard goes in my chicken pen. It comes up in many smaller pieces, but it's definitely not broken down. Generally when I put it in the chicken pen is when I remove any packing tape I hadn't removed previously. If I pull it up in the fall I try to re-cover the soil with the contents of the chicken room (straw bedding). Even when I don't put all the pieces of cardboard in the chicken pen until spring (and they go in multiple layers, as the pumpkin patch is at least 3 times the size of the chicken pen) all of the cardboard is "gone" by late June.

I think this combination (straw on cardboard) is a little too encouraging for squash bugs, but I tend to keep them down with hand to bug combat (boy, do they smell odd when you smash them) and I really appreciate not having squash and tomatoes go bad from sitting on soil, since sometimes a week will go by without me getting back to the patch to check on things.

Adam Briggs wrote:But you still run into problems of ink and glue going in the ground. Especially with the old carpet. Lots of glue and toxins there.

I do not recommend these methods.

I agree. Even soy based ink can have toxic pigments if you used colored papers. If you do use cardboard (and I do occasionally when I am mulching an area for a future fruit tree) be sure to avoid waxed (petroleum derived), colored, and cardboard treated with fungicide (some vegetable boxes).
Unless the carpet was all natural materials....like jute or wool or cotton or hemp with no backing and I was sure it hadn't been treated with anything, I wouldn't want it in my garden.

I want my soil as pure as possible and we have a perfectly good recycling center nearby that takes all paper including magazines, pasteboard (cracker and cereal boxes, etc) all cardboard (except waxed or treated so I avoid bringing those home for any reason)..

Peter Herrel wrote:I think that the more organic material you piled on that cardboard the faster it would decompose. I have an old hemp shower curtain that I'm going to experiment as a grass suppression layer in a sheet mulch this winter.

Do you have any pictures of the cardboard underneath the straw? How much straw was used exactly?

Not to answer for Jason.

Here are some photos of my orchard grass suppression project. I been slowing adding to it all summer. I'm shooting for about 6" of compost.
http://s67.beta.photobucket.com/user/eric_wa/library/Double%20Dog%20Farm%20Orchard%20Summer%202012

About once a week I stop at our local freight house and come home with a truck load of cardboard. The appliance boxes are my main target. I'm also on a call when ready, about every 2 weeks, I pick up 1 to 2 truck loads of horse manure. I love free stuff.

Couple problems I see with my project. My ducks seem to enjoy resting in the deep mulch bedding, but I'm stealing all their green forage. Not sure, maybe I have replaced it with more slugs and bugs.

Voles is the other problem. They love to shallow tunnel just under the cardboard. I lost a Kingston Black apple to these bastards, but that was before the cardboard project. Time will tell if have aided to the problem.

I wasn't concerned with any toxins in the cardboard, but deworming medication in the horse manure crossed my mine.

Eric

G-day Eric (i.e. DoubleDogFarmer). last year i used Patricia Lanza method of growing potatoes which is to lay down a layer of cardboard, place potatoes directly on the cardboard and cover with lots of straw.
when i harvested the potatoes 6 months later all trace's of the cardboard were gone.

A cardboard alternative -
I've used strips of old carpet as mulch.  The water goes right through but, the weeds don't.
We managed to find earth tone carpet, so you had to be really close to it to realize it wasn't soil.
I tacked it down with large staples I made from old wire hangers.  The little slits I cut for the staples where the only places I had weeds come through.  In the couple places where I weighed down the carpet, no slits - no weeds.
We could go out and harvest in the rain and not get our shoes muddy.
With what I know now I'd do one thing a little different.
I'd lay it out in pieces no more than 8 or 10 feet long.  Then as I had enough chop & drop material, I'd replace one strip at a time with organic mulch.
It didn't take very many calls to find a carpet layer who was happy to have me take the old stuff he was pulling out of a house.  He had to pay by the ton to take stuff to the landfill.  By meeting his crew at the home they were working at, they threw it in my pickup instead of loading it in their van.  They were happy since it meant one less time of them having to handle it.
You can't be picky though.  You get whatever carpet they happen to be pulling that day.

Judith said, "Do you know what the carpet is made from?  I think an all wool or cotton with no backing might be nice in the garden and decompose along with the other mulches.

More things to consider when thinking of using carpet:

https://permies.com/t/57872/carpet-path-mulch-weed-smother#489814

Anne Miller wrote:

Judith said, "Do you know what the carpet is made from?  I think an all wool or cotton with no backing might be nice in the garden and decompose along with the other mulches.

More things to consider when thinking of using carpet:

https://permies.com/t/57872/carpet-path-mulch-weed-smother#489814

The carpet we used didn't have padding.
However, considering what it was made of wasn't part of my thought process back then.  In my mind I was getting free mulch and keeping stuff out of the landfill.  Which, I was doing, but, at the time I wasn't thinking about what type of carpet cleaning chemicals were in the carpet.  I imagine those chemicals were being rinsed into my garden soil with each rain.  Now, I'd thoroughly rinse the carpet before putting it where I'm going to grow food.

For those of you concerned with the glue used in cardboard, you shouldn't have to worry about it; almost all glue used in corrugated cardboard is starch based. If you are using brown cardboard, the inks used are typically vegetable dyes too.  So a win win.

Be very careful with old carpet....it must be of a natural fibre... the synthetic stuff when broken down leaves a horrible mass of stringy fibres that can't be planted into , doesn't break down any further and if abandoned and left for grass  to grow through it, can't be mown without getting tangled in the mower blades....