Fall is a natural time to layer up, with clothing, comfort food and compost.

As you gather up the grass clippings and fall leaves, consider that they don’t always have to be tossed into a special bin, or built up into a square pile in order to be composted.

There are many methods to compost yard and garden debris. One of the most enduring and least work-intensive techniques is called sheet mulching.

Also known as lasagna composting, sheet mulching is an ancient technique that has many practical applications today.

Sheet composting is a "cold" or "passive" composting method used by people around the world for generations. This "no-dig" gardening technique attempts to mimic the natural process that occurs in healthy forests when the leaves fall, layering over organic matter from the previous season to form a thick, nutritious mulch.

It is an excellent way to convert grass into vegetable beds, create new perennial borders, improve soil and soil structure, buffer against drought, and recycle organic materials at home.

Sheet composting stays true to the fundamental principles of other backyard composting techniques in that it needs carbon (browns), nitrogen (greens), oxygen and water in proper proportions to break down fallen leaves and grass clippings into workable soil.

Sheet mulching has several advantages over other composting methods:

n It is a great way to take advantage of the rainy seasons.

n It is an easy and uncomplicated way to expand a garden with a minimum amount of equipment, material and time.

n It can be done bit by bit as materials become available.

n It can be done on both large and small scales.

n It can be used to improve soil in any area of your garden while adding on to borders and planting beds.

Sheet mulching is best started several months prior to the time you want to use the planting bed. Fall is the perfect season for this.

With the help of the rain, materials break down slowly through winter. By spring, the space is ready for planting. The basic practice involves layering carbon (brown) materials and nitrogen (green) materials directly onto the grass or soil.

For decomposition to occur evenly, layers of these materials should be evenly distributed. Aim for 1-inch layers, though you can go deeper if your material load allows.

1. Begin by mowing grass or other vegetation down to the lowest possible level in the spot you plan to lay out your sheet compost.

2. Ensure good drainage by aerating and gently loosening the soil under the bed with a spading fork.

3. Cover the ground with 4-6 overlapping layers of newspaper or cardboard. This carbon (brown) material smothers the grass underneath by preventing the penetration of light to allow for photosynthesis.

4. Wet the newspaper or cardboard thoroughly, and cover with a 1-inch layer of nitrogen (green) material, such as manure, fresh leaves or grass clippings.

5. Come back and top this nitrogen (green) layer with 1 inch of brown leaves, straw, shredded paper, wood chips or other carbon (brown) material.

6. Continue to add alternating layers of nitrogen (green) and carbon (brown) materials until you’ve reached a final height of 18 inches to 3 feet.

7. As the materials slowly decay, you can continue to add layers of nitrogen (green) and carbon (brown), always ending with a carbon layer. This is the “blanket layer” that discourages flies from laying eggs on exposed nitrogen (green) materials, such as grass clippings or fallen orchard fruit.

While the height of your sheet composting beds might vary, generally the thicker the bed, the longer the materials will take to decompose.

If having a cleaned-up look is important to you, you can use burlap coffee sacks to create a final layer. The burlap will decompose over time but can be removed in the spring when it comes time for planting.

Things to remember

n Sheet mulching is a slow process. There is little to no heat reaction from the micro-organisms to speed things along.

n The process in full may take up to six months. A bed is finished and ready when the layers have decomposed to the point that the original material are no longer recognizable, and it looks and smells like fresh, sweet earth.

n This is one of the best methods to remove grass from any area of your yard. Leaving grass intact allows topsoil to be retained and beneficial organisms to thrive.

— Callie Martin is a Waste Reduction Recycling Education Specialist with Skagit County Public Works — Solid Waste Division. She can be reached at 360-416-1575 or calliem@co.skagit.wa.us.

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