Let's go round again...
Many thanks for your recent enquiry regarding the crops you’ve been growing in your polytunnel. I'm off my feet and out of the garden at present, courtesy of a broken ankle, so apologies for not responding immediately to your enquiry.
But back to your question! Crop rotation is an essential part of good garden husbandry and in your situation, I would divide the growing area you have inside your polytunnel into sections (preferably 4, but 3 if you can’t manage it) and rotate your crops in this way. I would imagine you will be utilising your tunnel to grow out of season as well, and as long as you ensure that the rotation plan is adhered too, you hopefully won’t come across any of the soil diseases which rotation aims to prevent. Digging in plenty of organic matter whenever possible and removing debris from preceding crops will both help, and please do not lose sight of the fact that crop rotation does not represent a complete prevention or cure to pests and diseases!
You might want to consider using raised beds or other planters, such as growing bags and spud tubs, elsewhere in the garden to help address the issue of space and crop rotation. You will also find monthly updates from our own Kitchen Garden – that is when the gardener hasn’t injured himself!