Having lost all of my outdoor tomato plants this year through "Blight" should the ground be treated before trying again next year, and, if so, what with and when?
Help appreciated. Thanks.
Glyn, common tomato fungal problems - Early Blight, Septoria Leaf Spot, etc - aren't soil-related. The spores travel in the air. Some of the spores will fall from the leaves to the soil during the season, but, as I posted above, you can turn over the soil and bury them. Any of the same fungal problems that turn up next year will arrive through the air.
The blight that attacks both toms and potatoes is Late Blight. Late Blight spores, unusually, don't live on in the soil on their own. They only remain an ongoing problem if infected toms - or potatoes - are left lying around.
There is, though, as Phil says, an argument for not planting in the same ground in successive years. There are some diseases - mainly viral - that can live on in the soil.