[solway cropper]

There's a farmer/grower near here who's had potatoes growing in the same field for the last four years. I used to wonder if he'd ever heard of crop rotation but I know how he does it now. Last week he was coming out of the gate with a spray boom on the back of the tractor. Kill everything that isn't a potato. 

[Salmo]

If they are earlies he will be OK. Many fields in Devon/Cornwall used to grow early potatoes followed by Spring caulies year after year on the same field. These were special fields that were sheltered and faced south. They were often so steep that they were set and lifted by hand.

The main risk is that eelworms build up. The potatoes are lifted before the eelworms can produce egg cysts and multiply.