I have composted small amounts of clippings in the past with the other
compostable material, but I don't whether such a large amount of ivy
composted by itself would prove toxic to the soil.

Why on earth should it? If it did, every time an old tree fell down
in the UK, there would be a sterile patch ....

We've composted and used ivy (shredded) for years and it's never done any
harm. In fact we've even used the shreddings stright on the soil with no
problems. It gets scattered, turned and, er, fertilised by the hens which
I'm sure helps.

Mary


Regards,
Nick Maclaren.