Garden

Compost Soil Thermometer

Those making compost often wonder how they'll know when the pile is hot enough to properly compost the material and when it is cool enough to use. Learn how the best way to monitor the temperature.

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Credit: Sheena Adams

Composting is a great way to recycle yard and kitchen waste into nutrient-rich soil for the garden.

Those making compost often wonder how to know when the pile is hot enough to properly compost the material and when it is cool enough to use. In other words, how do you monitor the temperature? The solution is simple: a compost thermometer. Any gardener with a compost pile the size of half a picnic table or larger will find a compost thermometer helpful.

When micro-organisms do their work of breaking down a pile of compost, heat is released. The hotter the compost, the quicker it is decomposing, the more sterile it will be and the less chance you will have of introducing weed seeds or harmful bacteria into your garden. There are many different types of thermometers available. The most easily found are stainless steel probes with a clear dial.

Just be sure to get one long enough to reach the centre of your pile (about 50 to 60 cm/20 to 24 in.) and one that reads up to 104°C (220°F). To take a reading, place the probe in the centre core of the pile. Hot compost, which is very active, should read 54 to 65°C (130 to 150°F). Partially decomposed compost should be 32 to 43°C (90 to 110°F). And when there is no heat left and the original ingredients are unrecognizable, you’ll know your scraps have turned into beautiful compost ready to use in your garden.