Sheet composting is a way to dispose of waste and get the benefits of decayed organic matter without building a compost pile. The techniques of sheet composting range from spreading the organic waste directly on the soil, to digging it under, to liquefying it and pouring it around plants. Mulching with an organic material is nothing more than sheet composting at its simplest—the organic material breaks down slowly and is pulled into the soil by earthworms and other soil life.
Sheet composting on the surface
The most common type of sheet composting involves layering organic waste over a garden area and tilling it in with a hoe, spade, garden fork, or rotary tiller. Almost anything that goes into a compost pile can be sheet-composted. Leaves are the ideal organic material, since they’re easily tilled into the soil and decompose rapidly. Grass clippings, manure, and food waste (except meat and meat products) are also effective materials. The best course is to shred or chop the material before you layer it.
To sheet-compost in fall, spread a 4- to 6-inch layer of organic materials on the soil surface. To do it in spring, spread a 2- to 3-inch layer about a month before planting time. If you don’t have enough nitrogen materials, you may want to spread some granular fertilizer at the same time to help stimulate the decomposition process. Then work all the material into the soil. A tiller is the best tool to work compost material into a vegetable garden. In a flower bed, where you don’t want to disturb perennials and bulbs, work in the organic material carefully with a garden fork or hoe.
If you sheet-compost in fall, the organic materials will have largely decomposed and blended into the soil by spring planting time. A sheet compost started in early spring won’t be as thoroughly decomposed, but you’ll be able to plant after four or five weeks.
The Double-Digging Technique
If you plan to double-dig a garden bed as a way of preparing the soil for planting, you can incorporate sheet composting into the process. Double digging consists of scooping out a trench about 1 foot wide and 1 shovelful deep across the bed, loosening the soil at the bottom with a garden fork, then replacing the top layer of soil.
To incorporate sheet composting, add a 2- to 4-inch layer of organic material after loosening the soil at the bottom of the trench. This added step effectively raises the bed a few inches and improves drainage. The added organic waste breaks down slowly, leaving the soil loose, friable, and more fertile. Although double digging requires considerable physical effort, it need only be repeated every few years. For best results, double-dig in fall to give the organic waste time to decompose before spring planting.
You may prefer this technique if most of your garden is always planted, making surface composting or double digging difficult or even impossible. With a posthole digger, dig holes 6 inches in diameter and 12 inches deep near shrubs and other perennial plants. Into each hole deposit shredded or chopped yard waste or kitchen scraps. Refill the holes, burying the waste. When you collect more waste, dig more holes and fill them. This is an effective method for disposing of limited quantities of organic material.
Liquefied Food Waste
Kitchen scraps, except meat products, can easily be turned into liquid form for use in sheet composting. A heavy-duty blender or food processor can reduce rinds, peelings, and other waste to a puree that can be poured directly onto garden beds and around trees and shrubs. The puree decomposes where you pour it. Gardeners who compost this way report no odors or pest problems. The technique also eliminates the need for fertilizer in areas where the liquid waste has been applied. Within about two weeks the material is pulled into the soil by earthworms and other soil organisms.