It’s a busy time for gardeners—even if it’s still chilly outside many of us are starting seeds, planning our garden layouts, or otherwise getting ready for gardening season. This makes it a good time to talk about soil health and some ways that you can build and maintain good soil in your garden. For this article we’ll discuss sandwich composting. This layered approach to composting can take place directly in a garden bed or even a container, and offers a number of advantages for all types of gardens. It might be the right choice for your garden space this spring, so let’s dig in and learn more about sandwich composting!
How Does Sandwich Compositing Work?
Sandwich composting is what it sounds like: creating layers of compostable materials so that the layers vaguely resemble the layers of a good sandwich. You may also see this referred to as “lasagna gardening” or “sheet composting”, which also described the layered nature of the compostables.
By building materials in layers within the garden bed, sandwich composting creates a good mix of ingredients to create great, compost-rich soil as the materials in the bed break down. This attracts healthy soil microbes and earthworms while also providing a nutrient-rich place for plants to grow. Sandwich composting can create long-lasting nutrition and soil health, making it an increasingly popular choice for gardeners of all types.
The Basics of Sandwich Composting
While there are a number of different approaches to sandwich composting, a basic and commonly used formula goes something like this.
First, assemble the materials:
· Cardboard
· Newspaper
· “Brown” materials, meaning materials rich in carbon: leaves,straw, dried grass clippings, old mulch, or shredded wood and bark.
· “Green” materials, meaning materials rich in nitrogen. These include things like fresh grass clippings, veggie peelings from the kitchen, coffee grounds and used tea leaves, fresh plant clippings and trimmed leaves, or freshly pulled weed (make sure no seeds have formed!).
· Good manure from chickens, rabbits, horses, or cattle—avoid using manure from humans or carnivorous animals like cats and dogs. Cat and dog manure may transmit harmful microorganisms to the soil. Human manure can make good compost but it needs to be handled carefully and that’s beyond the scope of this blog.
· Good topsoil
· A accessible supply of water
Once your materials and equipment are gathered in your garden area, let’s make some layers. The first step is to cover the bottom of the raised bed or dug-out garden with cardboard, followed by some newspaper until the combined layers are 2 inches/5cm thick. Water these layers with a hose or water can—watering helps get the decomposition process moving along so you want each layer damp but not soaked
Next we’ll add a layer of “green” materials. These can be all mixed together in a relatively thin (less than 2 inches/5cm) layer. Water this layer as you did before, and then it’s time to add a layer of “brown” materials on top, followed by—you guessed it—another watering. Do the same with a thin layer of manure, and then a layer of topsoil. You can add more “browns” on top of the topsoil to help protect it and retain moisture by acting as a mulch.
Sandwich Compositing in Spring and Fall
There are a handful of seasonal considerations for sandwich composting, depending on whether you’re starting your sandwich beds in the spring or fall. If you’re starting them in the spring with the goal of planting in them that season, we recommend adding a mix of top soils and peat moss between the upper layers of your sandwich in order to give your plant some soil to get started in. The lower layers will break down as usual over the spring and summer and give your plants some much-appreciated nutrition.
If you’re starting your sandwich garden bed in the fall and you don’t plan on planting till spring, you can add a bit more manure and “green” or “brown” materials. They’ll break down into compost over the course fo the winter months and be ready for your plants when spring comes.
The Benefits of Sandwich Composting
Sandwich composting fills many roles: it makes good use of materials that might otherwise be discarded. It builds healthy soil in a long-lasting and relatively low-cost way. And for us gardeners, it helps us learn a bit more about how soil works, how composting happens, and how both of those benefit our plants. If you have some space, consider giving sandwich composting a try!
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