Understanding compost lab analysis reports helps you evaluate whether a compost product meets the quality standards needed for your intended application.

Key Parameters in Lab Reports

  • pH: Most plants prefer compost with a pH between 6.0 and 8.0
  • Electrical conductivity (EC): Indicates salt content; high EC can harm sensitive plants
  • Carbon-to-nitrogen ratio (C:N): Mature compost typically has a C:N ratio between 10:1 and 25:1
  • Organic matter content: Higher is generally better for soil-building applications
  • Moisture content: Affects handling, weight, and application rates
  • Particle size distribution: Different applications require different textures
  • Maturity and stability: Ensures compost won't compete with plants for nitrogen or generate excess heat
  • Heavy metals: Must be below regulatory limits for safe use
  • Pathogens: Fecal coliforms and Salmonella must meet safety standards

How to Read a Compost Data Sheet

Reputable compost producers provide data sheets showing their product's test results. When reviewing a data sheet, compare results against the specification requirements for your intended use.

Testing Programs

  • US Composting Council Seal of Testing Assurance (STA) — requires regular independent lab testing
  • State and local regulatory requirements for commercial composting facilities

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