Interesting comments here, thanks. Over the long term we are now saving money by growing our own in quantity but it would certainly be easier to use the supermarket! However, you’d miss all those other lovely benefits of growing your own food, my primary two motivations being health followed closely by taste.
Regarding green manures equalling a zero sum return, wouldn’t organic matter and fertility have never naturally increased any where if this was the case? Energy is taken in from the sun and you end up with a physical addition to the soil – possibly a bit like the difference between taking a vitamin and mineral supplement instead of eating veg/ fruit that provides both the former and with the addition of fibre too.
It’s nearly time for the gun to go off, although it seems Charles has already started! Enjoy the coming season all.