Would this be legal and in so anyone willing??

No it is NOT legal.

Australia Post works closely with Quarantine and they will spot your package and will likely consfiscate it. If this doesn't happen, likely your country's quarantine will spot it coming in the country and will do the same.

Soil can habour all sorts of living organism which can and WILL cause harm to the environment of the destination country. (Many people may think "What's a big deal?" but there was a case of a small beetle was brought in - not intentionally - on a souvenir that was not declared at the border entry. This little bugger, of course - reproduced, and caused millions of dollars worth of damamge to the wheat industry here in Australia. The reverse can happen to other countries)

to find out if its legal, call the post office and ask them. cuz thats who you would probably go through when its mailed. Or call UPS or FedEx or whomever you think you might go through. sorry i live in the US also

you can not send dirt through the mail, even if you have dirt on your shoes through customs any country they have to clean your shoes - for a fee of course, for protection ....

The last I heard, that would 'not' be legal.