Hi,
Im like a stuck record on this point, but here goes anyway....
To develop a good rotation system (ie to give the ground chance to recover) you need to know if your pigs have a worm burdon or not, and what type of worms they have. Some species of worms can lay dormant in the soil for upto 5 years!
So once you have established your worm position and worming treatments, then you can establish the best rotation and ground rest period for you.
Ask your vet about worm egg counts or do a postal count. I would say who does postal counts, but that would be advertising