I wrote a paper about sheet mulching for my soils class. I thought maybe some people on here might enjoy it. Feel free to leave me feed back, positive or negative. If there is anything you do I would love to hear because i might just add it to the final draft Plant lists would be good too. Also if anyone who reads this has better idea for formatting or grammar, I am not good at that so if you have tips, thanks!
Building Soil the Permaculture Way There is more life in a tea spoon of soil then there are humans on Earth. I have no idea where that statistic actually comes from or which scientists figured out how much life is in a tea spoon but, that quote is in almost everything you read about building healthy soil. There are trillions of microscopic and some not so microscopic life forms living in the soil, all of which play a role in helping the soil environment thrive. If you want to grow the best food crops you can, or if you want to grow the most beautiful flowing plants you have to pay attention to what is alive in your soil and what you put in the soil.
Before I go on to describe how to build soil in a permaculture way, I must first define permaculture. Permaculture is a design science that draws from many disciplines including, organic farming, ecology, agroforestry and sustainable development, in an effort to create agricultural systems that mimic that of a natural system.
In nature fertile soil is built by organic matter piling up, decomposing, piling up and decomposing. To mimic the natural cycle and to add a heap of healthy soil amendments to an area that needs improvement you simply have to add organic matter. Falling leaves in the forest recycle nutrients to the soil for the trees. You can just dump leaves on the ground and wait to see the pocket of improved soil you have created, it is not the most effective but it can be done.
Permaculturists have created a technique that uses the add organic matter cliché in a way that optimizes efficiency; they call it sheet mulching. The most basic form of sheet mulching starts with simply lay down a layer of, one or all of the following, compost, manure, and composted manure. You then cover that with a layer of a weed barrier, usually cardboard. Lastly on top of the cardboard you cover it with a thick layer of mulch material. This mimics the A and O layers of the soil, with the addition on a weed barrier to keep out unwanted plants.
Adding Oxygen The first thing you will want to do to a site loosen it. Depending on how compacted it is there may be little to no life in it. The amount of weeds and the amount of diversity of weeds is a good way to judge the life of your soil. Tilling up your soil destroys the ecology of the soil, exposes microorganisms the sun, and causes erosion. Instead of tilling, there are a few options you can do to loosen and aerate the soil. The first and easiest is to acquire a broadfork. A broadfork is a tool that looks like a giant fork with a bunch of teeth, looks sort of like a pitch fork. It is used to break into the soil but instead of turning the soil over, you push down on the broadfork to pry it up and loosen it up. Using the broadfork method allows you the same ease of planting as a tilled field except that you have not disturbed the microorganism in the soils environment as much.
The second idea that I enjoyed and consider to be the more fun way to do, although more time consuming is breaking the soil with the use of pigs. Pigs are natural plows. By allowing pigs in the area for short monitored periods of time you will benefit by have to do no physical labor to loosen the soil, fresh manure will be added to the soil, and you will have pasture raised organic bacon.
It is best to sheet mulch during the fall so that come spring time you will have a beautiful garden bed ready to plant. This will also give time so that the weed barrier can decompose fully so your crops have an easier time penetrating though.
Adding Moisture The night before you plan on laying down the sheet mulch give the area a very nice wetting. The soil organism need the water and since by the end of the next day it will be covered in many layers of organic matter it'll take a lot of water to penetrate down there.
Adding Organic Matter The next thing you do to an area after breaking up the soil with either a broadfork or swine is to cover it with compost. You can make your own compost by piling up layers of green and brown materials. Green being freshly cut plants and brown being twigs, leaves and straw. It is good to put a thick layer of woody material on the bottom to allow oxygen to flow in and out of the pile. The chances that you be able to create enough compost on your own to sheet mulch and area really depends on the size of the area, the amount of materials you have, and the amount of work you are willing to do. It really is exciting to spread compost you have made yourself, so you can always just add it to compost you've bought.
If there are plants you consider to be weeds in the area cut them done as close to ground as you possibly can. It is okay to leave the roots of the plants in the soil, under the weed barrier layer they will die and begin to decompose. The roots underground will release beneficial nutrients into the soil and become pockets of humus. Worms will show up, beneficial microorganisms will show up and they will begin to help improve the soil as well. The weeds that you have removed can be left on the ground under the weed barrier, the tops of the weeds, like the roots, will become food for beneficial organism in the soil.
Once the weeds on the site have been dealt with the next step is to spread a thin layer of organic compost on the soil. If you left the weeds, sprinkle it right on top of them, this will add decomposing microorganism. This is also a good time to add any soil amendments that your soil might need to get to the proper pH. After that, then the weed barrier can be added. The weed barrier is the only item in this process that does not have a counterpart in the natural forest system, in the forest weeds do not grow because there is simply no room for them (also in the forests they are just called plants). Things that make good weed barriers include, burlap bags, old clothes, corrugated or non corrugated cardboard, six to eight layers of newspaper, not the shiny kind. Although most newspapers still used petroleum based inks, some are switching to all or some soy inks. Using newspaper is allowed on organic farms.
On top of the weed barrier is the layer that everyone has their own opinion on. The good news though, is that sheet mulching is a very forgiving practice and as long as you are adding organic matter to the area your soil will be improving. If you have manure for any animals you keep, chickens, pigs, goats, rabbits, or horses, it is best to place them right on top of the weed barrier. You do this because if they are not fully composted or dried any smell will be covered by the next layers.
The next best thing to do on top of the manure level is to lay down a an eight to twelve inch thick layer of seed free hay or straw. Continuing with the idea of hiding manure, if you have any soiled hay from an animal house, chicken coop, pig pen, goat yard, rabbit hutch, or horse stable, the mixture of manure and straw will do very nicely here. Also, any leaves you have gathered can be mixed into this level as well. I believe this is a good idea because if you just add the leaves to the top of the system they have the potential to be blown away. Not only would that create a mess but it would also take away the organic matter you had added. It is also a good idea to moisten this level for the same reason you moistened the ground, it will help the soil organism.
On top of that layer add another thick layer of compost. One to two inches is good, but two to three is better. This composted layer will contain beneficial organism that will help break down the manure, straw, and leaf layer below. The last layer after that is another dressing of a few inches of straw. The sheet mulch is down.
Planting If the soil is really compacted there are root crops that have reputations as being excellent drills. That is their roots just drill into and bust up the soil, diakon radish are the most famous in the permaculture community. You can either start the diakon radish in seed starting trays or sow directly into the upper most compost layer. You can harvest and enjoy the radish at the end of the season or you can let it die in its place. As is decomposes worms and other soil organisms will move into it and when they are done it will be an excellent pocket of humus in your once compacted soil.
Tuber crops, like potatoes, are another choice. To plant tubers just dig a small hole into your sheet mulch place the tuber and then cover it with a few handfuls of soil before recovering with sheet mulch materials. This is the same with sweet potatoes and yams. Some people have success with planting large seed plants like beans and peas into the sheet mulch too. The same technique is used, pull back some sheet mulch place the seed, then cover with soil, and replace the sheet mulch.
If you are using sheet mulch in an area that you are not ready to cultivate but do not want the weeds to spread to your cultivated areas you can use this opportunity to plant trees in the Fabacaea family. Trees in this family are nitrogen fixers. You could plant such trees as Tipuana Tipu and Jacarandas for their beauty, acacias for their shamanic purposes, or trees like black locust which is an excellent goat fodder. When you are ready to cultivate that area you can cut down these trees and use them for fire wood, chip them for mulching, or use them in hugelkulture (a soil building technique that involves burying trees and branches either in trenches or to create raised beds).
Conclusion Sheet mulching is an excellent way to create a ready to plant garden bed without doing any digging. It can completely choke out fields of obnoxious weeds. It is an excellent way to compost on site, recycle materials into the garden, and save organic matter from the landfill. In fact many of the materials can be acquired for free.
In most suburbs we now have green waste collection, these bins offer endless supplies of organic materials from your neighbor's yard. Also, because it is best to do this in the fall you should have no problem gathering leaves from your neighborhood. Tree services and landscapers might be willing to dump waste at your yard instead of paying at the dump. If you are lucky maybe a grocery store or restaurant will give you old produce, Starbucks gives away their old coffee grounds. Fairground events are away to get cheap or free barely used hay bales and Dairies, hatcheries, and ranches are excellent places to get manure (be carefully with these places, factory farms use heavy amounts of antibiotics).
If you are experiencing a problem in your garden look to nature for the answer. Forests provided us with an excellent idea on how to avoid labor intensive practices when it comes to amending and loosening the soil.
Nice paper, Alan. Since you requested a plant list, I have attached my plant list for the food forest that I am planting in my back yard here in central Florida, zone 9A. All the plants that have a number entered under the "quantity" column are actually in the ground and established. The others are plants that I am considering, or that I will definitely be planting as time and resources allow, such as the chestnut, jujube, and pawpaw trees for example. This list is a "living document" as they say and it will be revised constantly, both in terms of adding new plants that I learn of and possibly deleting plants from the list if I determine they are either not hardy in this location, require too much maintenance, could be invasive, or any other problems. Most, if not all of the plants on this list should be pretty good candidates here in this location, I'm just not 100% sure quite yet. If anyone knows of any reason not to plant any of these here, please let me know.
Certifiable food forest gardener, free gardening advice offered and accepted. Permaculture is the intersection of environmentalsim and agriculture.