Posted: 21/07/2012 at 12:56
Getting rid of the soil is a bit extreme. In most garden circumstances, the soil is part of the garden and is not normally removed. Sensible crop rotation should keep further crops from being infected by the soil.
But that is only if it's soil-borne in the first place. Blight spores are normally brought in on the wind, in warm damp conditions. Even spore-free soil can't protect from that. The evidence on it remaining active in the soil seems a bit scant, and it's perfectly OK to use the soil for unrelated crops or for ornamental plants.
And for what it's worth, I accidentally planted tomatoes in a bed that had blighted potatoes in it last year. I have sprayed them twice with Bordeaux Mixture, and there's very little sign of blight yet despite the weather - less than in previous years when I was careful to rotate the crops. This year's potatoes, which are in blight-free soil, are a bit of a disaster, as they were very slow to grow, and the blight stopped them in their tracks before there were many potatoes.