One of the most important characteristics of a compost is its electrical conductivity (EC), which is a measure of the soluble nutrients in the compost. This will define if a compost can be used as a growing medium (EC3), or is more like an organic fertilizer (EC>10).
These composts may look exactly the same (see photo below), but if you use a high EC compost as a growing media, the plants will be dead within 48 hours due to an osmotic effect that will pull the water out of the plants. Conversely, if you use a compost with a low EC as a topdress on your lawn, don’t expect much growth.
Composts originating from yardwaste alone have a low EC (not many soluble nutrients), whereas the EC (and soluble nutrients) increase with increasing amounts of foodwaste in the compost. Animal manure based composts typically have a higher EC, but is dependent on animal type and composting process.
I am advocating that composts be marketed with their EC clearly identified, so that potential users can understand what the compost can be used for.
