Thursday, August 20, 2009

Learning from Nature with Sheet Mulching

This is the fifth article in an ongoing series that I've written in our town's alternative paper, the Madison County Crier. The series is intended to be an introduction to permaculture, often illustrated by examples taken from our homestead. When possible I've also made it a point to link in to the potential for a permacultural approach to town and community life as well as the prospects for easing our town's transition into this new future we have before us.

In my last article I discussed relationships as they exist in garden guilds and in town communities such as Fredericktown. Much of permaculture is about how we design relationships into a site so that things such as plants, animals and buildings work better together and so require less energy input from us. This week I thought I’d focus on a very practical hands on task that, while seeming very simple to us, enables complex natural processes which increase the health and diversity of our garden soil: sheet mulching.

Walk out into any mature Missouri woodland of diverse trees and dig our hands down into the soil and you will find fantastic fertility. At any moment woodland soil is full of organic matter in the process of decay. Fungi and soil microbes are constantly breaking down leaves, sticks and any other “dead” matter that has fallen to the forest floor. According to Jack Kittredge in the Spring 2002 issue of The Natural Farmer:

... it is hard to overestimate the importance of mushrooms in forest life. Their mycelia form a complex forking network of interwoven strands of cells that grow beyond the immediate tree’s root zone, extending, in extreme cases, over many acres. The mycelial content of topsoil in a Pacific Northwestern Douglas Fir forest has been estimated to be as much as 10% of biomass! Each mycelium gives off
enzymes which unlock organic compounds in the surrounding matrix, releasing carbon, nitrogen, and other elements that are then absorbed and concentrated directly into the network.


Modern agriculture, as it has grown from small family farms to massive acreage industrial farms, has taken an approach which relies on fossil fuel-based chemicals for fertilization and the removal of “pests”. It is an approach which has decimated the natural fertility of complex soil ecosystems. Even small scale vegetable gardening is most often accomplished with tilling which greatly disrupts the natural microbial layers found in the soil. Opening up the bare soil to the direct sun and wind is not only destructive but is an open invitation to weeds and the need for more work or the use of chemicals.

The no-till method of gardening using heavy layers to form a thick sheet mulch creating conditions very similar to a forest floor: carbon rich, shaded, cool and moist. Pull back a section of sheet mulch which has set for six months or more and you will find a great abundance of earthworms, far more than were there before the mulch. A close examination of the newspaper or cardboard will also reveal many patches of intricate white threads, the mycelium of soil fungi which have been busy breaking down the carbon. The soil is so thoroughly tilled by the earthworms and the crumb structure improved that you will usually be able to easily push your fingers deep into the ground with little effort.

Now, let’s get down to the how-to. Sheet mulching is incredibly easy but may require a bit of planning to save or collect the materials needed. You’ll need lots of newspaper, cardboard, or both. Nothing with waxy coatings and bright colors such as many of the advertisement sections of the paper. We want basic newsprint and basic brown cardboard. Ask around the businesses in town and they are often glad to have someone take it away. The amount needed is determined by the size of garden space. The other ingredient is something like straw, leaves or wood chip mulch. Straw works very well because it will last a full year, won’t blow around and looks pretty nice. Wood chip mulch also works well but cedar and pine may increase the acidity of the soil avoid those woods as well as anything which is treated. Leaves tend to blow around and don’t look as nice. If you have lots of leaves use them but top off with straw or wood mulch for a tidier appearance. Aged manure or compost can also be used and will speed the process up a bit but are not essential ingredients.

Step one is to water the area to be mulched. I often plan to do it the day after a rain. Basically, the ground just needs a good watering as you might do if you were watering a garden or lawn. If you have compost or manure spread it over the area to be mulched in a layer three inches or less. Next comes the cardboard or newspaper which should be laid down so that it overlaps a couple inches on each side. Don’t spread too thin. If using newspaper open it at the fold then lay it down. If the layer is too thin it will break down more quickly and may not last a full year which is the goal. Follow the cardboard/newspaper layer with straw, leaves, or wood chip mulch which should be laid down in a layer of about three inches. Give this layer a light watering. Done.

Laying the mulch should be done in spring, summer or fall. I think spring or early summer is best. You can mulch directly over hard compacted grass without mowing or any other preparation but this area won’t be ready for planting right away. In areas which have been mulched for at least 4 to 5 months the soil is often improved enough to plant in fairly easily. This spring I’ve been working in a bed which was mulch last summer and the soil is greatly improved. The cardboard is very well rotted and can be easily pushed through with a small hand shovel for putting in plants and seed potatoes. For direct planting of seeds I can easily clear away a row or area with hoe or hand shovel.

When we sheet mulch not only are we using “waste” materials such as newspaper and cardboard, we will find that the need to water and weed are greatly reduced. Not only are we more efficiently using resources and saving ourselves time but we are greatly improving the stability and health of our soil.



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1 comment:

  1. Denny - I only came across your blog today but have already enjoyed reading a couple of your permaculture posts.
    I'm gathering my materials to get into sheet mulching for the first time.
    It's spring now over here so the timing is right - just need to decide where to start first!
    James

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