Comparison of Compost Maturity Assessed Using the UK Tomato and German Barley Plant Response Tests

Abstract Plant response tests are popular with some European composting industry schemes compared to seed germination only tests. In the case of the UK tomato plant response test, this assesses not only seed germination and plant growth but also weed germination and plant abnormalities (the latter due to presence of herbicide residues). However, a drawback of the test is its long duration at 28 days slowing positive release of finished compost. The purpose of this pilot study was to carry out a first-time comparison of the UK tomato response test with the German barley response test which is shorter in duration at 10-12 days. Eleven compost materials, both finished composts and immature material, were run on the tests in parallel with supporting sample characterization to aid results interpretation. The two plant response tests reported comparable pass/fail results for nine out of eleven samples. The two remaining samples were reported differently and neither test reporting fail in both instances.