The best way to keep microbes in your compost bin munching away through this long hot summer is to ensure they have enough water to survive.
Heat means that activity in the bin speeds up, using up more water, so as always with composting, keep an eye on your bin. The microbes need air and water as well as food or they will die off and composting will stall.
How to tell if compost is too dry
The ideal moisture consistency is about 50 per cent, making compost as damp as a wrung-out sponge.
You can test this with a soil moisture meter, if you like a bit of kit, or go old-school by doing the squeeze test: take large handfuls of compost from different areas of the bin and squeeze – one or two drops of liquid should come out. If there’s no sign of liquid the compost is too dry.
Adding water to dry compost
Right now your compost could be very dry, especially if you’ve been away and there have been no fresh additions of wet materials such as food scraps.
* A quick fix is to water the compost - early morning or late evening is best to stop water from evaporating too quickly. If you can, used stored rainwater from a water butt rather than tap water since chemicals in the water system that are safe for humans can kill some of the microbes in your compost. Add water using a small watering can with a fine rose spray, targeting various dry places as you turn the compost.
* Make sure you keep adding wetter materials to the bin such as fruit and veg peelings so you're adding moisture. Normally at this time of year you would also be adding fresh grass clippings but green grass feels like a distant memory at the moment.
* If you have a lot of shredded paper and cardboard (rich in carbon) to add to your bin, make sure you’re also adding equal amounts of food waste so the compost doesn’t become a dry compacted block. Conversely, if you’re adding a lot of fruit waste, make sure you’re adding enough shredded paper/cardboard/woodchips to absorb liquid so you don’t encourage flies.
* On top of your compost create a covering layer of dead leaves, soil or mature compost – this will help to lock in moisture. It will also prevent smells and so deter flies.
Top additions for dry compost:
* Chopped watermelon rinds are an excellent source of slow-release hydration.
* Used coffee grounds add moisture without causing unpleasant smells. Cafes and restaurants are usually happy to give these away to composters.
Throw some shade
Protect a bin that's in hot sun by creating shade with tarpaulin, cardboard or shade cloth.
Time to move?
If this summer has shown you that your bin’s position has left it too exposed to baking hot sun, it could be time to rethink the location. Harvesting your compost in autumn would give you the opportunity to relocate to somewhere with some shade.
As always with composting it’s a balancing act between the right amounts of heat, oxygen, moisture and materials.
A little composting management keeps everything ticking over nicely, especially your munching microbes.
