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News Release

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Making the most of your compost

URBANA, Ill. – After the fall, many homeowners wonder what to do with the leaves that have accumulated on the ground.

“Composting can be a beneficial process to manage yard waste,” said University of Illinois Extension horticulture educator Andrew Holsinger. “Proper planning and effort can provide the opportunity to generate organic matter beneficial to the soil.”

Composting is defined as the transformation of raw organic materials into biologically stable humus-like substances suitable for growing plants. “Organic matter improves soil quality in a number of way,s including, soil moisture retention, nutrient-holding capacity, and nutrient cycling,” Holsinger explained.

Nutrient-holding capacity is the ability for soil to hold nutrients that would otherwise leach away, and nutrient cycling is basically recycling nutrients that were previously taken up by plants.  The cycling of nutrients balances the availability of nutrients from the plant material back into the soil.

What are the keys to success when it comes to composting? 

Compost materials are made up of a proportion of carbon to nitrogen in an organic material.  When these materials are combined in proper proportion and in combination with air, water and warmth, it creates a proper environment for decomposition.

Decomposition is what is desired when it comes to composting, Holsinger explained.

“Unfortunately, during the winter months, some of these key components may be lacking to achieve the success desired in decomposing your organic waste,” he added.

The key components are the following:

  • Temperature: Compost piles should be covered in the winter.  Covering the compost pile in the winter excludes excess rain or snow, which can make the pile too wet.  Insulating the pile in the winter has the benefit of reducing cold air, which can decrease microbial activity.
  • The carbon to nitrogen ratio: There are two main components of organic waste that are transformed to compost: the green materials (nitrogen or N) and brown materials (carbon or C). 

Nitrogen is used to build proteins (amino acids).  The microorganisms need nitrogen in order to survive. There is a shortage of nitrogen in the soil because everything living wants to consume it and it can be leached away by rainwater. The green materials are sources of nitrogen and protein. Usually they consist of fresh green plant materials, including fresh grass clippings and organic food waste. Never use dog, cat, raw hog manure, or human waste because these can contain potential biohazards that can be harmful to family members.

Carbon is used for energy by microorganisms.  Sources of carbon differ in their chemical structure and some can be challenging for microorganisms to digest.  The brown materials are also absorbers of excess moisture.  Usually they consist of dried brown plant materials, including ground-up leaves and straw.

“It is important to have an optimal ratio of carbon to nitrogen which is typically 30:1,” Holsinger pointed out. “If there is too much nitrogen in the mix, the compost pile can become too hot, which may kill the compost microorganism, or it may go anaerobic, resulting in a stinky mess.”

He added that with too little nitrogen in the mix (high C), the compost will not heat up properly, which could result in a longer waiting time for finished compost. This ratio is most important in the breakdown of the compost materials to feed the microorganisms the proper diet of carbon and nitrogen.

Air:  Composting materials are broken down by aerobic organisms, which require air for their survival.  In high-temperature situations, it can help reduce odor. The initial moisture content of composting materials tends to be high and can be reduced with aeration. Turning of the compost pile is the most common method for aeration. Other methods of aeration include passive aeration with a network of perforated tubes or using an aerated static pile.

Water:  While moisture is a requirement for composting, high moisture results in a reduction in the pore spaces for air.  Low moisture deprives organisms of needed water for metabolism and inhibits their activity.  Ideally, home compost piles should contain 45 to 65 percent moisture.  The ideal moisture for most materials is 55 percent. You can check your moisture level with a simple squeeze test. Squeeze a handful of composting material, forcefully, and check for drips.  The compost should feel like a wrung-out sponge.

To make the most of your compost, follow these helpful tips.

  • Mix the pile as needed to reduce moisture and odors
  • If the pile is too dry, add water until there is the feel of a dampened sponge
  • Keep meat products out of the pile to reduce animal and insect pests
  • Cut or chop organic materials to increase surface area for quicker breakdown (optional)
  • Cover compost pile with a tarp to retain heat in winter
  • Increase volume from the ideal size of 1 cubic yard to 4 feet x 4 feet x 4 feet if pile is located near windy area (optional)

News source:  Andrew Holsinger, 217-532-3941, aholsing@illinois.edu

Source: Andrew Holsinger, Extension Educator, Horticulture, aholsing@illinois.edu

Local Contact: Candice Miller, Extension Educator, Horticulture, mille116@illinois.edu