Stephen Wolstenholme wrote:
Someone suggested a while back that the best* way to sterilise some
garden soil or manure for putting on mushrooms would be to 'bake' it
in the oven.

What temperature and for how long would be effective?

I'd use the microwave, much easier

Most microwaves will not sterilise dry soil. The soil will have to be
wet all the way through. A bit like cooking a mud pie.

Wet is not currently an issue!