Here's the plan for this year as dictated by the rotation. The Brassicas area gets lime. The Others area gets manure and the Roots area gets some compost in with the potatoes. As each area rotates over three years they all get the treatment once every three years and the pests don't get a chance to build up.
BUT I have made the adjustments to the overall plan as detailed in the second picture to meet my own priorities for this year. I don't need such a large brassica patch and if I am determined to grow carrots. So the potatoes are being squeezed between the soft fruit and the other roots. Answer: to borrow a bit of the brassica patch for the parsnips and carrots, with the proviso that next year (when this is the roots area) potatoes will be grown here and not carrots or parsnips again.