Do I Have Humus in my Compost?
Wednesday, 5 February 2014 | HOTBIN Composting
Compost contains humus, but there is no standard set for how much (the %). We believe most mature composts have around 10% (+/- 5%) humus. If you compared this to a commercial 'humic fertiliser' derived from ligninite, this would have >65% humic content. The exact amount of humus is likely to vary with each batch of compost.
Compost is not routinely tested for humus/humic content. The key reason for this is due to the complexity and cost of testing for fulvic acid, humic acid and humin - they need complex laboratory tests to determine its presence.
We have found the following indicator useful (based on a the key property of humus - ie it is a colloidal material):
Take a handful of compost and squeeze it - it should ooze moisture between your fingers. Now roll between your palms into a ball. Leave the ball for a couple of hours in the sun (or on a dry surface). Come back and try rubbing the dried ball between your fingers.
NB: this method is used in soil science to indicate the presence of colloidal clays. So, if you have added a lot of soil or turf sods to your compost you will probably just be noticing the effect of clay rather than humus!