I usually grow two tomato plants outside in huge plastic pots filled with compost. At the end of the season, I empty the spent compost on the flower beds as a mulch, and the next time start afresh with new compost, after having well washed and cleaned the pots. I think this prevents disease from lurking about any new tomatoes. As my requirements are few, two plants well fed and tended give me massive amounts of tomatoes. I stick a great big long cane down each pot before planting, and tie the plant to it gently as it grows. I just adore the smell of newly picked tomatoes, they're full of flavour and nothing like Tesco's offerings! In fact, isn't there a world of difference between home-grown fruit & veg and the supermarket apologies for same?