About Composting


Mario Villarino DVM, Ph.D. Hopkins County Extension Agent for Ag and NR, 1200B Houston Street, Sulphur Springs, Texas 75482 903-885-3443

As we prepare for spring planting, many growers and gardeners are looking for good soil mixes to start their crops or gardens. An excellent option is composting at home. I have included here technical data from Texas AgriLife Extension related to home composting.

In the home place are many sources of raw materials for the compost pile. From the kitchen comes coffee and tea grounds, and vegetable and fruit trimmings, which amount to 0.2 to 0.9 pound (90 to 400 g) per capita per day. From the landscape comes leaves, grass clippings, brush trimmings, old plant material, and many weeds, yard trimmings that represent 15 to 20% of the municipal waste stream. Leaves present less of a challenge in both collection and composting than do other organic sources while representing a major portion of the waste stream. In most cases the home compost pile will be built with landscape trimmings and rakings. Starting with leaves and grass clippings, for example, and adding some brush or wood chips for a bulking agent could prove to be the right mix to begin composting in the first year. Kitchen wastes can be added to the pile as they occur.

Most all organic materials will compost, but not all of them should be put in the pile. Some organic wastes will attract rodents, dogs and cats, while weeds and pathogen-infected materials may survive the composting process. Also, fatty foods and bones should be avoided because they will attract rodents and create odor problems. Cat and dog fecal materials as well as cat litter should not be used in the pile due to harmful pathogens. In looking at compostable materials one consideration should be the amount of time each material needs for breakdown. High nitrogen materials, like grass, will break down very readily while wood chips may take up to two years to reach the humus stage. The higher or wider the carbon:nitrogen ratio (C:N), the longer time it will take for breakdown to occur. Coarse materials, such as straw, nut shells, corncobs and stalks, will also take longer to breakdown. However, the greener and more succulent the material, the quicker the breakdown period.

All materials that are high carbon should be cut or shredded into small pieces and mixed with high nitrogen materials, such as manure or fresh grass clippings. Do not discount the rough or coarse materials because they can be used as bulking agents in the pile. Coarse matter will break down slowly in the pile and will improve the pile structure by allowing air circulation. A bulking agent is very important when there is not a good mixture of materials or when raw materials tend to pack together. It might take several attempts to get the right mixture of materials that will give you the perfect recipe for composting. Mixing different types and sizes of organic materials will provide a well- drained and arable compost pile.

The more varied the materials going into the pile, the better chance of maintaining the proper C:N ratio and efficient decomposition. Microorganisms need nutrients, primarily carbon and nitrogen, for both energy and growth. The ideal carbon:nitrogen (C:N) ratio is not found in any one organic source. However, it is possible to create compost out of primarily one raw material, such as leaves. Due to their high carbon content leaves may take 5 months to 2 years to compost by themselves. However, leaves will compost and turn out a good finished product if moisture is adequate and if the pile is turned frequently, ensuring a good supply of oxygen. Mixing other organic wastes with leaves to utilize these other sources in recycling is important. The high nitrogen source, such as grass clippings or other plant wastes, animal manures, food scraps or other high nitrogen materials can speed up the decomposition process and increase the nitrogen content of the end product making it more suitable for use as a soil amendment. The high nitrogen component must be carefully controlled because the addition of too much nitrogen can result in the formation of ammonia, creating an odor problem.

The rapid decomposition also uses up oxygen, causing further problems as the aerobic microorganisms are replaced by anaerobic ones. Grass clippings are high in nitrogen and can be added to the leaf pile. However, high moisture and high nitrogen content in the grass clippings require that they be mixed into the pile with other materials in order to reduce the anaerobic conditions that can occur from grass being “clumped together” in the pile. Research conducted at Rutgers University by Dr. Peter Strom indicates a mix of 2-3:1 (leaves:grass clippings) as being the optimum for decomposition in the compost pile. However, as the material decomposes, the problem of maintaining an optimum leaves:grass ratio increases. After leaves are collected in the fall and wind-rowed, they undergo a substantial reduction in volume due to the burst of microbial activity that occurs within the first month of composting. By the time grass clippings are being collected the following spring and summer, the leaves have been reduced in volume as much as 50%. If leaf/grass clipping mixes are to be composted, leaves collected in the fall should be stockpiled without turning until grass collection begins. At that time, form a pile with the appropriate mix of stockpiled leaves and grass clippings. The leaf piles will likely be anaerobic and some short term odors may be generated when the piles are disturbed. Leaves act as a bulking agent, allowing more oxygen into the windrow to maintain aerobic conditions. Grass clippings, because they are high in nitrogen and moisture provide needed nitrogen and speed the decomposition, and restore vigorous composting activity to pile.

Again, experimenting with mixes is a good way to find the mix that works for you. It should be noted that grass clippings do not need to be removed from the lawn when mowing. If lawns are mowed frequently, and the clippings allowed to fall back into the lawn, their collection is not necessary. Grass clippings, being high in nitrogen, will decompose rapidly and actually return nitrogen to the soil, reducing the need to apply nitrogen in the form of fertilizers.

For more information on this or any other agricultural topic please contact the Hopkins County Extension Office at 903-885-3443 or email me at [email protected].


Author: Staff Reporter

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