Blossom end rot is not a disease, not a fungus, and almost never a shortage of calcium in your soil. It is a water supply problem inside the plant, which changes entirely what you should do about it.
Crop rotation rests on two specific mechanisms, not on a magic rule. Here is how to think in botanical families, why nightshades deserve your attention first, and how to make trade-offs when your plot is only a couple of hundred square feet.
There is no single correct distance between two tomato plants. Here are the three variables that decide it, the spacings most growers work from, and how to adjust them for your own plot.
Late blight is not a fungus, and that distinction explains everything else. Its biology sets the terms: liquid water on the leaves and a moderate temperature. Everything that actually works consists of denying it those terms.
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Diseases
Rotation
Tomato
Turn the reading into a garden.
Marmanda turns this advice into a dated, placed plan for your own plot.