Let’s get the obvious question out of the way first. Do you need a compost thermometer?
And the answer (drum roll please) is not if you’re composting at home. If you’re a commercial compost maker, then perhaps you have a need for one but then again, you already know that.
Home Gardeners Need To Know…
If you’re a home gardener, here’s what you need to know.
If the compost pile is large enough, (roughly 4x4x4 feet) and is filled up at one time with compost-ready material, then it will start to heat up.
It will take several weeks to do this. At the two week mark after building the pile, lift it up and see if it is hot inside. If you can comfortably lay your hand on the hot material, you’re fine. If your hand is too hot for comfort you’re getting to the point of good composting.
Put the layers back down and walk away.
As soon as the pile starts to cool down or you see some crystallization starting to form (white powder – resembling ash) then you know it is time to turn that pile as the heat has done its thing.
If you’re using one of the smaller home composters that don’t get a hot composting system going, then you really don’t require one at all because there will be nothing to measure.
Doug’s Summary Notes
Use your hand as the compost thermometer.
If your hand is comfortably warm – the pile is either beginning to compost or finishing off composting.
If your hand is too hot – the pile is in full compost mode.
If it’s not hot at all, then you have another issue to deal with and that’s the carbon:nitrogen ratio or brown:green ratio.
One of the things we have to get straight here is our definitions of what we’re talking about when we talk compost tea. So here’s what happens when you don’t make compost tea but rather these other systems.
In simple terms, compost tea is an extract of compost where the bacteria, fungi, protozoa, and beneficial nematodes are increased in numbers using nutrients and oxygen provided by the gardener. In short, oxygenated tea made from compost.
Manure tea. This extract can contain soluble nutrients such as nitrogen, phosphorus, and potassium but it also contains high levels of bacteria. In many of these bacteria, such as E. coli, are not things that you want to put on your garden. Manure tea also often contains high numbers of root feeding nematodes.
Compost extract. This is produced by draining water through a compost pile. It contains soluble nutrients such as nitrogen, phosphorus, and potassium but very few beneficial microorganisms. Given that there are not high levels of these nutrients in compost, this is pretty much a waste of time but a relatively harmless practice.
Compost leachate. This is what is produced when compost is super-saturated and the water is collected. This leachate contains only the soluble nutrients and very very few beneficial microorganisms. One of the problems with compost leachate is that it is quite possibly anaerobic and not something we want to add to our garden. Different kinds of pathogens live in anaerobic (without oxygen) water/tea.