tomatoes and potatoes are the same family, so would be the same year in the rotation. Roots usually follow brassicas because they don't do well - or some of them don't - in soil that's rich. Basically it goes manure the bed, plant potatoes. Second year beans and peas which like the reasonably rich soil. Then brassicas follow because they like the nitrogen left by the peas and beans, and finally roots because they do best in relatively low food soil after the brassicas have taken most of the goodness out. Then manure and start again. If your potatoes went in with plenty of fertiliser, then might be best not trying carrots. Parsnips may be OK, best bet would probably be salads,or spinach, chard, or beetroot (all the same family) or add more manure and have courgettes or cucumbers.
So grow your tomatoes and potatoes in grow bags or pots this year, also grow carrots in pots. Your 3 beds would be beans and peas in one, brassicas in another (you may need to give them a bit of a feed) and spinach, beetroot possibly courgettes and salad in the third. Next year grow brassicas where the beans were, carrots, parsnips and garlic where the brassicas were, and if I were you, peas and beans where the 'others' were. Only try potatoes/tomatoes in the third year, following the brassicas, having added plenty of muck first.
ETA - there's talk these days that strict rotation isn't really necessary. The main point is to not grow either potatoes/tomatoes or brassicas in the same place 2 years in a row, preferably with a 3 year gap because both have diseases that can stay in the soil and affect the following year's crop. Onions also are best not grown 2 years in a row in the same place. But peas and beans, courgettes and squash, salads, the beet family are all pretty much fine either moving around or in the same place. So use them in any order you like as the fillers to allow you to move the rotating crops as needed
Last edited: 21 February 2017 13:40:03