Agriculture Reference
In-Depth Information
Sheet Mulching
Sheet mulching is kind of like composting right in the garden, mostly to create new
garden beds and in existing vegetable beds during the fallow season. The ingredients are
the same, with the addition of a weed barrier layer made of some kind of easily available
natural material — cardboard and newspaper are most commonly used. Some people are
concerned about the glues in cardboard and inks in newspaper, but they're mostly fairly be-
nign and should be broken down by microbes. I wouldn't use glossy or colored paper.
Sheet mulching is an amazing way to smother weeds and build fertility and structure at
the same time by layering various materials as high as 18 inches. It has a few advantages
over composting, perhaps the biggest being that it's less work. Once you put the materials
down, that's where they stay, whereas with composting you generally turn it a few times
and then have to move it into the garden. It takes longer to break down than compost, but
that also means it lasts longer as a mulch.
At the same time, it generally doesn't get hot enough to kill weed seeds and pathogens.
If you keep a continuous mulch, most of the weeds will be taken care of anyway. If you're
using a diversity of materials from good sources, the few pathogens you'll be introducing
will be taken care of, too. Unfortunately, some tenacious weeds can be introduced with
sheet mulch, giving you months and years of work to get them out, so for some people, a
proper compost pile can be less work in the long run.
If you already have slugs, you'll probably have more when you build a sheet mulch.
They love the stuff. That's one reason why I put my garden in a sunny, hot spot and don't
over water, but a few seem to show up anyway. There are plenty of ways to take care of
them organically.
There are many methods of making a sheet mulch. I start with a ½ inch layer of newspa-
per or cardboard on the ground to suppress weeds, and then water the heck out of it.
There's no need to pull the weeds first. Even if you do this on a lawn, you don't have to till
up the lawn first — just mow it short and leave the clippings there. In fact, a sheet mulch
can be a handy way to deal with weeds you don't want to put in your compost or with turf
you've removed from somewhere else in the garden — just throw them under the weed
barrier layer.
Then use all the same ingredients you would in a compost pile. Many people like to
build it in layers, which is why it's sometimes called a “lasagna” bed. From the bottom up,
it might look something like this: fertilizers such as calcitic lime, cardboard, one inch depth
of manure or other nitrogen materials, eight inches hay or straw, one to two inches com-
post, and two inches straw or leaves to top it off. I prefer to mix the manure/nitrogen mater-
ials and hay/straw together using two to three shovels of carbon material for every shovel
of nitrogen material, but the bottom and top of the pile look about the same. I also use all of
