One of the many techniques that we were exposed during our internship at Green String Institute was sheet composting. I enjoy this method a lot, as it involves building soil rapidly, making use of 'waste' products from elsewhere while being incredibly easy to do. Seriously, this involves literally piling up and wetting necessary materials to get going!
Sheet Composting involves layering of organic materials to create a raised bed or mound that can be sown with plants of your choice. The organic materials are chosen such that they have the right carbon-nitrogen ratio so that they can compost on the same site that the plant is being grown. In this way, sheet composting is a lot more effective and convenient that making a compost pile elsewhere and spreading it around in your garden beds. Furthermore, you can plant in your sheet compost bed immediately if you use a layer of compost as your top layer. But that's getting ahead of the steps!
Let's get started:
Step 1: Gather materials
These are the materials that you would require for your sheet compost bed:
- Amendment Layer - This layer includes all amendments that you might want to put in your soil prior to making the sheet compost bed. This may include lime, blood meal, crushed rock dust, etc.
- Barrier Layer - This can be any material that would act as a barrier to the plants growing underneath it. Suitable materials would include cardboard, stacks of newspaper, burlap bags, etc.
- Organic Matter Layer - This layer requires two different types of organic material. First, you need organic matter that is high in nitrogen. This includes materials such as any animal manure, green grass clippings or green weeds. The second type of organic matter is one that is relatively high in carbon. This would include materials such as hay, straw, wood shavings, yard waste, shredded leaves, etc. The end result with this layer is to get a carbon to nitrogen ratio of around 30:1. As a ball park this means getting roughly the same volume of high nitrogen material: which are fresh green materials, and carbon material: which are dead brown materials.
- Compost Layer - This is the layer that you plant directly on. Make sure that you have good quality, diverse compost.
- Mulch Layer - This can be any type of mulch material, such as straw, wood shavings, shredded leaves, etc. The most important thing about this layer is that it has to be seed free, since it is on the top and can cause problems if unwanted seeds germinate.
Step 2: Pile it up!
Its not time to get your pile on. Before beginning to pile, water the area that you wish to sheet compost the previous night, and put your fork in and out of it lightly right before you start to pile the materials. Cut (not uproot) any existing vegetation to the ground.
First, you put on the amendment layer if you need to. This layer helps if your soil is deficient in a certain type of nutrient. Amendments such as crushed quickly cooled igneous rocks contain any and every trace minerals that you would want to add to the soil. A thin dusting of this layer should be sufficient.
Then, you start to lay on the sheet. Big pieces of cardboard usually work best. Overlap the cardboard so that you fill up any bare ground, and water thoroughly. This layer will act as a weed barrier. if you are using newspaper, make sure it is at a similar thickness to regular cardboard.
Now you can start to add on the bulk organic matter. Mix the carbonaceous and nitrogenous materials together and layer slowly, moistening them as you go. This layer needs to be about 8 to 12 inches.
Step 3: Make it pretty (and practical)
Now that you have piled up all the organic material, you can start to add the final two layers. First add the 1-2 inch thick compost layer. This is the layer that you sow your seeds, or plant your transplant into. Make sure it is good quality compost so that the seeds or plants get the necessary nutrients.
After you plant whatever it is that you desire, you can mulch it up with the final layer. Mulch helps in water retention, protection of soil from the elements as well as in providing food for soil biology. As mentioned before, you should make sure that the mulch material is seed free to avoid feeling discouraged when grasses take over the bed when they start germinating! This layer can be around 2 inches thick.
And there you have it. You can have an almost instant garden with this method and get planted right away. The only caveat to this method is that you will need a hefty amount of organic material at hand, which may not be practical if you are working with a large area.
Interestingly, the garden area around the intern house sits on soil made through sheet composting over several years. The sheet compost was lain on a once barren parking lot, which has now been transformed into a highly productive garden space.
Shesan P. Intern - Winter 16