Composting Series: Determination of Compost Maturity

Juan Calix, Dunaway, Christopher R., Kuehny, Jeff S., Adhikari, Achyut, Hammett, Bert, Timmerman, Anna, Willis, Joe

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Composting is complex process which involves several cycles such as carbon or nitrogen production. Carbon and nitrogen production is directly affected by how much microbial activity there is in the compost pile. The best time for compost to be used for plant growth and development is once it is mature. A compost is considered mature once it moves from a phase of high microbial activity to a phase of low microbial activity. During this maturity phase most, organic materials will have broken down to useful humus and also carbon and nitrogen production will have been reduced.

Why is compost maturity important?

  • Immature compost, can cause phytotoxicity to plants
  • Low aeration needs
  • Raw materials have broken down
  • Low aeration
  • Better consistency and smaller particle


Methods for Evaluating Compost Maturity

MethodHow does it work?Considerations
Chemical MethodsMeasures chemical changes in the compost such as; Cation Exchange Capacity (CEC), Carbon and Nitrogen Ratio (C/N Ratio), Nitrification, or pHMeasures chemical changes in the compost such as; Cation Exchange Capacity (CEC), Carbon and Nitrogen Ratio (C/N Ratio), Nitrification, or pH
Biological MethodsMeasures the phytotoxicity of a compost by determining if germination is affected by the compostCan be done in a household setting, however it may use up valuable seeds.
Microbiological MethodsMeasures microbial activity;

Immature compost=Microbial activity is high

Mature compost=Microbial activity is low



Uses indicators such as; CO2 and NH3 production or Biological Oxygen Demand (BOD). May need laboratory services however household tests are available (Ex: Solvita Compost Maturity Test
Spectroscopic MethodsMeasures the ability of light to refract through compost samples in order to measure how much humus may be in the compost pileDoes not destroy sample when analyzing, however, there is a need of complex spectroscopic equipment
Degree of HumificationMeasures the degree to which organic matter has degraded into humus, which is easily used by plantsSeveral ways of measuring mathematically, but needs certain measurements such as acid contents or carbon content which need to be measured in a laboratory
ChromatographicMeasures biosynthesis of acid in order to measure indirectly degradation of large compounds in the compostNeed of complex equipment and expertise in how to use them
Physical MethodsMeasures physical aspects of the compost such as; temperature, appearance, color, uniformity and odorDoes not need expensive equipment, however, these characteristics can be very subjective and therefore not good indicators at times. Temperature can be very reliable because it is measured, but it must done properly with a compost thermometer.

Solvita Compost Maturity Test:

This easy-to-use maturity test uses microbiological methods but removes the need for laboratory services. Throughout the composting process different microorganisms work at degrading large materials into smaller materials. In the process depending on what type of microorganisms are present, they will increase or reduce the production of two gases: CO2 and NH3. Once microbial activity is low (compost is mature) these two gasses will be reduced. The Solvita test contains two pallets, one measures CO2 and the other measures NH3. This is done by taking a small sample of compost, placing it in the provided container along with the two pallets. Then the container is sealed and after one hour the colors that appear in each pallet are compared to a maturity index provided with the kit and the stage of the compost is determined.Determination of compost maturity using Solvita test kits-WEBjpg
Determination of compost maturity using Solvita text kits.


Authors:

Juan Moreira, Research Assistant, School of Nutrition and Food Sciences; Achyut Adhikari, Associate Professor, School of Nutrition and Food Sciences; Christopher Dunaway, Assistant Extension Agent, Jefferson Parish; Bert Hammett, Extension Agent, East Baton Rouge Parish; Jeff Kuehny, Director, LSU AgCenter Botanic Gardens; Anna Timmerman, Assistant Extension Agent, St. Bernard Parish and Joe Willis, Extension Agent, Orleans Parish.

Visit our website: www.LSUAgCenter.com

Pub. 3838-F (Online Only) 04/22

Luke Laborde, Interim LSU Vice President for Agriculture

Louisiana State University Agricultural Center, Louisiana Agricultural Experiment Station, Louisiana Cooperative Extension Service, LSU College of Agriculture

The LSU AgCenter and LSU provide equal opportunities in programs and employment.

Funding for this publication is provide by the USDA NIFA FSOP Award #: 2020‐70020‐33035

5/2/2022 3:12:35 PM
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