Compost

Compost is perhaps one of the less understood and used contributors to soil organic matter and overall soil ecology and management. Compost needs to become another tool that farmers use along with cover crops, animal manure and other management strategies.

The word “composting” or some derivative has been used for centuries to refer to the slow natural breakdown and degradation of organic matter such as the decomposition of leaves and litter on the forest floor. During the last century and particularly the last few decades, “composting” is most often used to refer to the process of mixing organic matter at specific ratios of carbon to nitrogen and managing moisture, aeration, and temperature through various methods of piling, turning or mixing to achieve the desired stable and biologically active end product we call “compost”. Depending on many variables, the active composting process leading to a stable product can be completed in a matter of days, weeks or months and is then followed by a maturation phase of weeks to months that results in finished, mature compost.

There are several potential benefits to justify the added time and cost of producing compost including:

  • Volume reduction of bulky materials allowing easier transport and application.
  • Moisture reduction of manure or food processing byproducts for transport/application.
  • Homogenization or increased uniformity of a mixture of materials and particle sizes.
  • Stabilization of organic matter and nutrients to generally a less available form.
  • Weed seed reduction or degradation
  • Plant pathogen inoculum reduction
  • Herbicide, pesticide, antibiotic or other chemical contaminant degradation.
  • Development of a diverse and beneficial mix of active or dormant microorganisms that can be added to soils lacking desired biological activity.

The possible down side of composting includes:

  • Investment in time, labor and space to complete the process.
  • The loss of energy and carbon that could be used by soil microorganisms
  • The loss of nitrogen as a gas depending on the formulation and management of the pile

Application of compost to soil (depending on the rate applied) can provide an inoculum of microorganisms, slowly available nitrogen and nutrients, stable organic matter, and has been shown to reduce the infection rate and crop losses due to plant pathogenic root and foliar diseases.

The lack of availability of well made mature compost has limited it’s use in farming. We are seeing an increase in both on farm production of compost and the availability of compost from commercial processors for application on farm. Commercial suppliers of compost for farm application have had trouble meeting demand for the spring of 2005. A website to help with the purchasing or marketing of compost is available at: http://web2.msue.msu.edu/compost/

When making compost, please consider that the basic process of composting is not complicated and can be done many ways. However, there are several factors that influence the process of making compost so making a high quality product that is consistent over time does take experience and knowledge. Important variables to consider include carbon to nitrogen ratio, the inoculum of living organisms from the components, moisture, aeration, temperature, time of composting – which is influenced by particle size and pH. More recommendations about getting started in composting are provided in the Compost Production and Use document and the websites listed below.

The rates of compost being applied by farmers can range from 1 ton/acre (~2 cubic yards) applied with a lime spreader to 50 ton/acre applied with a manure spreader. The most common application range is in the 5 to 10 ton/acre. The availability, cost and quality of the compost and the desired outcome will determine which rate is practical.

As we work towards a greater understanding of soil ecology and management we likely will see a greater emphasis on compost production and use and more information to help farmers. Please start now on a small scale to learn more about making compost on your farm, using compost on your farm, and the availability of compost from sources near your farm.


Sources of Information:
   


© 2004 Department of Crop and Soil Sciences
Michigan State University. East Lansing, MI

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