Leaves, grass clippings and trimmings account for up to 20 percent of the landscape wastes in landfills. Many homeowners compost these materials for mulch or as a soil amendment.
Soils often can be improved and made more productive by simply mixing in organic matter. The most popular source of organic matter for soil improvement is livestock manure. Cheaper and more readily available sources of organic matter grass clippings, vegetable scraps, small twigs and fall leaves. To become usable soil amendments, these materials should be decomposed by bacteria and fungi. This process is called composting.
Bans on outdoor burning and laws that limit dumping of leaves and grass clippings into landfills make composting and mulching an attractive alternative. Some cities and neighborhoods provide composting areas, but it can be done in your own backyard.
Constructing a compost pile is easy, but there are a few rules to follow. The compost may be prepared in a bin or on the ground as a pile. Choosing the proper location for the compost is important. The pile should be located in an area that is protected from wind and receives partial sunlight.
The compost pile should be prepared in layers that are not compacted when added. The first layer is comprised of coarser materials, such as twigs or wood chips. Coarser materials decompose faster in the bottom layer. This coarse material also allows air circulation around the base of the pile, creating a chimney effect that will take air up through the pile. As materials begin to decompose, heat is created. Layering the compost pile properly allows the heat produced to travel from the bottom to the top layers and increases the rate of decomposition.
Moisten, but don’t saturate, all layers as they are put in the pile. Moisture is an important part of a healthy compost. Moisture encourages growth of bacteria and fungi that will decompose the plant materials. A compost pile might begin to smell foul if there is too much water added. Frequently turning the pile and adding more woody materials can decrease excess moisture.
After the coarse layer organic wastes, such as leaves, grass and plant trimmings, are put down in a layer 8 to 10 inches deep. These materials can be shredded or chipped. The next layer is an inch of soil or completed compost. This guarantees the presence of the necessary bacteria and fungi for decomposition.
Typically, organic yard wastes such as grass clippings or leaves contain enough microorganisms on the surface to allow decomposition, but the addition of soil or completed compost ensures their presence. Research shows that there is no advantage to purchasing a commercially available compost starter to add these microbes.
After the soil layer, a nitrogen source should be added. Decomposing microbes require nitrogen, and a lack of nitrogen will decrease the rate of decomposition in the compost pile. An excellent source of nitrogen is 2 to 3 inches of livestock manure. If manure is not available, a nitrogen source such as 10-10-10 fertilizer can be applied at one cup per 25 square feet. Do not use fertilizer that contains a herbicide or pesticide.
Repeat the sequence of adding coarse material, organic waste, soil and fertilizer until the pile is completed. Remember to water each section as you make the pile. The pile should be about 5 feet high when completed.
Certain materials should not be added to the compost pile because they pose a health risk or attract pests. Do not add human or pet feces, diseased plants, meat, bones, grease, dairy products, grass clippings recently treated with pesticides or herbicides, or inorganic materials such as aluminum, plastics or glass.
Next week’s topic will continue with the management and uses of the compost pile.