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Soil Magic with Sandwich Composting

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It might seem highly improbable that just a pile of cardboard, newspaper and grass clippings will magically turn into beautiful rich soil, but that is indeed what actually happens. I saw it with my very own eyes. In our quest to find more space to plant vegetables in our ever expanding garden, we did a trial sandwich composting project on the sunny, but weedy side of our house last October.

Now in spring, our simple compost sandwich has really turned out beautifully. This low-labor compost making method appealed to me instantly. I used  Chris McLaughlin’s system as a guide:

• You don’t have to pull up the weeds or other foliage first or dig the soil in anyway, just knock down any plants and leave them in place.

• Next you will add layers of flattened cardboard (about 2 inches thick), then

• Sheets of newspaper printed with soy-based ink (about 10 sheets thick)

• Add green materials such as grass clippings, plant material, or kitchen vegetable waste (about 4 inches worth, 2 inches if using grass clippings)

• Finish by covering with topsoil or compost

It is very important to sprinkle everything with water between layers, and adding topsoil or compost between layers helps speed up the process. Then leave it alone for a few months and let the de-composers go to work.

Constructing a compost sandwich with layers of cardboard, newspaper, compost and plant material

When is the Compost Sandwich Done?

In the San Francisco Bay Area, the sandwich will be ready for planting in about 6 months, but in cooler climates it will take longer. We made ours in October and by May the bed had been magically transformed into dark, rich, healthy soil with many fat, happy earthworms  — perfect for my heirloom bean project.

Heirloom bean seedlings in a sandwich-composted bed

When we started building our compost sandwich last fall, initially it was a small challenge collecting enough cardboard and newspaper; but it just took a couple of evenings of raiding cardboard that had been put out for recycling to do the trick. For newspaper, the local coffee shop let me take home their stack of unsold papers at closing time, happy that I would be turning them into soil.

It really hit home that all of this daily “waste” is actually such an incredible resource, far too precious to just throw away. Re-purposing these recycled materials into organic fertilizer was one of my most satisfying moments as a gardener. Transforming garbage into compost, now that’s real magic!

Photos: Thierry Sornasse and Urban Artichoke
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