Of all the tests in our suite, plant response testing is the one people grasp most quickly. It asks a simple, practical question: if you use compost made from your material, do plants grow well?
The idea
Compost is, in the end, a product to be used. If a material passes disintegration and biodegradation tests but the compost it produces stunts seedlings, it has not really closed the loop. Plants are sensitive, integrated sensors. They respond to the combined effect of everything in the compost, including things a chemical screen might not have been designed to look for and interactions between substances.
How it works in outline
Plants are grown in compost containing the biodegraded material and compared with plants grown in a reference compost without it. Typical things to compare are how many seeds germinate, how quickly seedlings emerge and how much growth they make. If the test compost performs as well as the reference, that is a good sign. If it does noticeably worse, something in it is holding the plants back.
Beyond “no harm”
We also look at whether the material enriches the soil. Natural materials and biomaterials can return carbon and nutrients, and for a business whose story is circularity, showing that the end product is a benefit rather than merely harmless is a strong claim. It is one thing to say a material does no damage. It is another to show something grows better.
Why it complements chemistry
Plant response and EcoTox answer related questions in different ways. Chemistry is precise and broad. Plants are practical and holistic. When both agree, you can be confident. When they disagree, for example clean chemistry but poor growth, that is a useful flag that something unexpected is going on and worth investigating.
Where it sits in the pathway
Plant testing generally comes after you know a material breaks down. There is little point asking whether compost grows plants if the material never became compost. A typical route is a Quick Screen, then disintegration and biodegradation, then toxicity and plant response.
If you would like to test the whole story from material to seedling, we would be glad to help.
By Authenticae. Back to the blog