Posted: 16/10/2013 at 21:27
Firstly I don't envy the job you have ahead of you!!
I created a veg patch in my garden 2 years ago and after removing the turf I came across heavy clay which would even when hit with a pick axe a tiny amount would be broken. The plot I had created is 10m x 6m, I needed a more radical solution. I did have a tiller which went on my old Ryobi expand it strimmer but it wouldn't look at it.
I bought a 6.5hp rotavator which after several runs over and over it eventually started to dig into it and it it got down to the depth of around 12". I have been gathering leaves from my entire street and making my own compost with all my hedge and grass clippings and it is paying off now.
I would recommend renting a rotavator for a weekend and spend a couple of hours working with it then take a break for an hour then go at it again. It is still heavy going using a machine, but a lot better than double digging.
When you are done plant potatoes and they will loosen it up even more, but the more leaf mould/organic matter you can put in the better.