I bought two organic tomato plants from TBG ( one “yellow pear” and one Heirloom Brandywine). Growing in pots, the leaves turned brown and dry looking early in the season, even with regular watering. Is this blight? I did get a fair number of yellow pear tomatoes but only two brandywine (actually three, but an animal bit one) I know tomatoes should not be planted in the same place year after year and I may have planted them in these pots one too many years. Can the soil be used for anything else? (or should I throw it out?)
Tomatoes are subject to several fungal diseases which cause the symptoms you describe. Here is an informative Toronto Master Gardeners post that describes these diseases and offers good advice: http://www.torontomastergardeners.ca/askagardener/verticillium-fusarium-or-another-ium/ Crop rotation, even in the smallest vegetable bed, or container, is a very good idea, and there are plenty of planners available online. Vegetables in the same family are subject to the same diseases: tomatoes are in the same family as potatoes, peppers and eggplants – the Solanaceae family. The Toronto Master Gardeners have produced a terrific fact sheet for the City of Toronto on organic vegetable gardening that discusses vegetable families and the basics of crop rotation: http://www1.toronto.ca/city_of_toronto/toronto_public_health/healthy_public_policy/pesticles/files/pdf/gardening_vegetables.pdf
Since you have had what is most likely a fungal disease on your tomatoes this year, it is a good precaution to dispose of this soil entirely, since soil-borne fungal diseases can remain in the soil through the winter, and to make sure that your container has been thoroughly cleaned before reusing it. Container soil can be reused if the plants in it have not had a soil-borne disease, such as verticillium wilt. Containers containing soil that has been used to grow tomatoes should be used for some other plant or vegetable in the following two years, a kind of container crop rotation. It is a good idea to renew container soil frequently, because the nutrients in it do deplete over time. Old container soil which is free from any evidence of disease, can be reused in another part of your garden, or added to your compost.