News from the Compost Certification Scheme

The latest news from the compost industry


Investigation into complaints about the plant response test

Posted: 14 August, 2018. Written by Gabor

The minimum quality requirements in PAS 100 include testing for minimum plant response following the methodology described in OFW004-006 'Plant response and weeds test for composted material', published by Wrap. Wrap concluded that the tomato plant response test is suitable for screening composts intended for use in agriculture and field horticulture and any significant negative response in the test sample is considered to indicate phytotoxic factors in the compost.

As part of the Compost Certification Scheme, REAL monitors the performance of each laboratory that is approved to carry out this methodology through annual audits. Audit reports from 2015-2017 showed that all laboratories complied with the requirements described in the test method. In early 2017 REAL was made aware that the number of failures on this test seemed to have increased during winter. Appointed Laboratories were contacted and an investigation was carried out by each laboratory that showed that the number of failures seemed to have increased during colder months.

In 2018 more plant response test data was requested from the laboratories to cover the latest winter period. Analysis of data from 2015-2018 confirmed that there was a notable peak in failures during autumn 2016 at one of the Appointed Laboratories, however there was no significant increase in the number of failures in late 2017 and early 2018 at any of the laboratories. Therefore it was concluded that the increase in failures does not appear to be systematic. REAL continues to collect laboratory results in its certification database and will monitor the trends as more data becomes available. The 2018 audit round at Appointed Laboratories is currently ongoing and results are expected in autumn this year which will provide more information about the test setups at each laboratory.

The short report about this investigation, available to download below, provides a short explanation about the fail/pass criteria of this test, the auditing that REAL undertakes and the outcome of the investigation as summarised above. The most important ongoing projects are also identified that are essential for improving quality assurance.

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