Effective soil treatments for the prevention of tomato blight include sand and organic compost. These should be spread in 4-inch layers on top of the existing garden bed to improve drainage and provide a drier growing environment. White plastic mulch heats the soil and prevents humidity.
Working powdered milk and crushed eggshell into the soil before planting tomatoes provides nutrients and helps ward off fungus. The tomato plant benefits from spraying with nonchlorinated compost water, and regular watering should be done at the base rather than over the entire plant. Buying blight-resistant plants is recommended. Rotating crops helps prevent recontamination.