What is sheet mulching? It is a technique used by gardeners to prepare garden beds without having to dig or till their soil first. It involves smothering your grass, or whatever weeds you have, with cardboard or thick layers of newspaper, and then topping that off with compost or lawn clippings. Over time, the cardboard breaks down into the soil, and the grass is effectively killed.
Step-by-step instructions:
1. Figure out where you want your garden space to be in the Spring
2. Lay down cardboard or several layers of newspaper on top of the new garden space. It is important that you overlap your pieces so that no grass or any plant material is sticking up. You are utilizing the cardboard/newspaper to smother light out from any unwanted plants - so make sure there is no green sticking through.
3. You usually need to weigh down the cardboard/newspaper. Some people use stones or pieces of wood. Other folks water the cardboard/newspaper heavily to keep pieces from flying away.
4. Next you layer something nutritious for your plants on top of the cardboard. This is usually compost, but it can be uncomposted kitchen scraps, grass clippings, or any other kind of green material that is capable of decomposing quickly. I have a friend who works at a sprout farm and he used partially-rotted sprouts for his layer - turned out great. The green matter or compost that you lay down will provide nutrition for the soil and for your plants in the Spring. This layer needs to be at least 3-4 inches thick.
5. Next you layer something "brown" on top. You can use straw, hay, wood chips, or any dead, dry material as a top dressing. The purpose of this layer is to protect the bottom layers. The top layer of mulch will trap moisture, keep soil from drying out and blowing away, and keep new weed seeds from landing on your bed and germinating. This layer needs to be 5-6 inches thick.
That's it! To sum up: its a smothering layer (cardboard/newspaper), a green nutritious layer (compost/kitchen scraps), and a brown protective layer (straw/wood mulch). Some people put the green nutritious layer below the smothering layer. Other folks add lots of amendments and soils in with the green nutritious layer. There are many ways to do it, depending on your soil conditions and preferences.
You just leave your bed sit over the Winter. When Spring arrives, your cardboard/newspaper layer and your green layer will be almost completely composted and ready for Spring plants. You just plant directly into the top brown layer.
Here is a video of one lady sheet mulching in her yard:
http://www.youtube.com/watch?v=S2K_uZnjRKk
Here is a video of Permaculture founder Bill Mollison sheet mulching to plant potatoes (the sound quality is bad):
http://www.youtube.com/watch?