How can I test compost?

Wednesday, 5 February 2014  |  HOTBIN Composting

Keeping track of time, temperature, odour and physical structure will help most users make an informed judgement on the quality of the compost. (Did the heap achieve 60C, has it been in at least 30 days, ideally 90 days. Does it look fine, well broken down material that smells ‘earthy’).

A germination test (eg cress seeds) is a good way to check your compost is mature and stable.

There are some tests that you can use at home/domestic environment – they tend to be a little expensive, so it really depends on what you want to prove.

The Solvita® Compost Test Ammonia and carbon dioxide are tested for and then related back to compost maturity and stability via a conversion chart. Easy to use, but possibly too expensive for home composter at around £120 for starter kit containing 6 tests, and around £80-100 for additional packs of 6 tests. (The good folks at WoodsEnd Laboratories now have a video on youTube for using Solvita tests kits.

LaMotte Humus Soil test kit Designed for soil (1-8% humus). It is a colorimetric comparison test. Soil or compost samples are processed with a weak alkali solution (sodium hydroxide) and treated with EDTA chelating agent. The filtered solution, or extract, has a distinctive colour which is then compared to a standard colour vial on a scale of 0 to 100. These range from light yellow to dark red. The darker the colour, the greater the presence of humus. The number that results is a relative number rather than a percentage, and is commonly known as "humus value".