Compost

Information from University of Kentucky Cooperative Extension Service publication AGR-204: Kentucky Master Gardener Manual

Compost is an excellent source of organic matter for garden soils. Composting also closes the recycling loop by turning waste materials into a soil amendment. You can make compost at home or buy commercially prepared compost.

Making compost

The key to composting is to supply a balance of air, water, energy materials (materials with a low C:N ratio, such as grass clippings, green garden trimmings, or fresh manure), and bulking agents (materials with a high C:N ratio, such as corn stalks, straw, and woody materials). You don’t need additives to stimulate your compost pile. You just need to provide conditions favorable for natural composting organisms.

You can compost in the following ways:

Hot (fast) composting produces high-quality, finished compost in six to eight weeks. To maintain a hot compost pile, mix together balanced volumes of energy materials and bulking agents, keep the pile moist, and turn it frequently to keep it aerated.

Cold (slow) composting requires less work than hot composting. Build the pile and leave it until it decomposes. This process may take months or longer. Cold composting does not kill weed seeds or pathogens. Rats and other pests can be attracted to edible wastes in cold compost piles.

You can compost fruit and vegetable scraps in a worm bin. This method works well for urban gardeners who have little space.

You can bury fruit and vegetable scraps and allow them to decompose in the soil.

Commercial compost

Yard debris is the major raw material in most commercial compost sold in Kentucky. Commercial compost also may contain animal manure, biosolids, food waste, or wood waste. Commercial compost is made on a large scale, with frequent aeration and/or turning to create conditions that kill weed seeds, plant pathogens, and human pathogens.

Using compost

Adding 1 to 2 inches of compost each year helps build a productive garden soil. You can till or dig compost directly into your garden or use it as a mulch before turning it into the soil. One cubic yard of compost covers about 300 square feet to 1 inch deep. In the first year after application, partially decomposed woody compost may immobilize some soil nitrogen, resulting in nitrogen deficiency for plants. If plants show signs of nitrogen deficiency (poor growth or yellow leaves), add extra nitrogen fertilizer (either organic or inorganic). In subsequent years, most compost contributes small amounts of available nitrogen to the soil.

It is important to know the source of composted materials derived from grass clippings or animal manure used as fertilizer amendments on your garden or landscape plants. Herbicide residues could be present that can cause injury to sensitive garden plants such as tomatoes and other broadleaf plants. Active ingredients in certain herbicide products applied to lawns can be retained in grass clippings, or animals consuming herbicide-treated pastures and hay can pass the material through the digestive system, so that the herbicide in the manure persists at concentrations that will cause injury to sensitive crops. Furthermore, the composting process may not fully degrade these herbicide compounds. To be safe, make sure that composted grass clippings and manure used on your garden or landscape areas have not been indirectly exposed to herbicides.