Look for OMRI listing if you market as organic, USDA Organic handling, and ISO 9001 for quality systems. Microbial and compost-tea products should be made on a GMP or food-grade line with pathogen screening for E. coli and Salmonella. The AJ Cosmo Labs app lets you filter suppliers by certification so you can verify OMRI and organic compliance before you ever request a sample.
Read the full guide on how to find a soil amendment manufacturer →