Back to top

Compost Analysis and Interpretation

Printer-friendly version

 Compost Analysis and Interpretation

Compost producers and users have many goals; sanitation (ex: kill pathogens, insect larvae, intestinal parasites, weed seed); bioremediation (ex: pesticides, petroleum contamination, sewage sludge); build soil organic matter, improve soil structure and moisture holding capacity, enhance soil microbial activity, or fertilize crops.  These goals can be achieved when compost goes through the stages of decomposition and is properly cured, matured or finished. Decomposition begins with sow bugs, dung beetles, millipedes, centipedes, beetles, mites, springtails, earthworms etc. breaking down larger pieces of organic debris, and then bacteria and fungi begin to decompose the matter further.  During the mesophilic (40-100°F) stage of decomposition, proteins, sugars, and starches are oxidized, the microbial population increases rapidly, and the compost begins to heat up. The thermophilic stage of decomposition is most rapid at 100-140°F, which is the temperature at which most heat-loving bacteria (such as the actinomycetes) are active and the most microbial activity in general occurs. One way to monitor your compost during the decomposition process is to smell it. If it smells like ‘earth’ that is a good sign that the actinomycete filamentous bacteria are producing geosmin  (the fresh earth smell) as they die off.  If the compost smells like sulfur, then the pile is likely too anaerobic and sulfur respiring bacteria are active. Finally, compost must cure and will be ready for use when it is about 86°F.  Keep in mind that vermicomposting occurs at cooler temperatures as it is driven by worm activity, and studies have shown that a long period (30-50 days) is required to kill any human pathogens that may be present in the parent material of the compost.

In Massachusetts, several regulations impact the way that compost is made and used.  If producing biosolids compost for commercial use, the EPA (40 CFR Part 503) requirements are: compost produced in vessels or using the static aerated pile method must remain at 131°F for 3 days or windrow compost must remain at 131°F for 15 days or longer being turned a minimum of 5 times.  Both Federal and State regulations also govern the heavy metal content of composts.  In 2014, Massachusetts placed a ban on the disposal of commercial organic wastes into landfills by businesses and institutions producing one ton or more of these materials per week.  Also, no leaves or yard waste are allowed in landfills. This regulation has increased the amount of municipal and institutional composts being produced and used across the state, especially in municipalities such as Worcester and Boston which require soil for growing food crops to be built on top of existing soils due to frequent historical lead contamination.  Finally, the 330 CMR 31.00 Plant Nutrient Application Regulations went into effect in 2015 requiring that all applications of plant nutrients, including plant nutrients in composts, be based on soil tests and UMass Guidelines (with some exceptions where guidelines do not exist) and that records of each application be kept by the applicator.  Nutrient management plans are required for application of plant nutrients to 10 or more acres of agricultural land.

There are many agricultural, environmental, and regulatory reasons to get a compost analysis and interpret results for plant available nutrient content. So how is this done?  Click Here.

Katie Campbell-Nelson
Last Updated: 
Nov 6, 2015
Agriculture topics: 
Soil and Nutrient Management