Rotation for well-rested soil
It is important to allow your soil to lie fallow, as well as to vary crops on the same plot if it has been cultivated for several years. For example, you should not plant celery, celeriac, or leeks in the same place for two years running, as these plants deplete the soil of nutrients.
Vegetables that take from the soil
Similarly, you should avoid growing cabbage-family plants (especially cauliflower), endives, spinach, cucumbers, squash, and corn if you have not prepared the soil with manure and compost. Rhubarb also needs extra organic matter each year.
Vegetables that give to the soil
After planting crops that use up the minerals salts in the soil, you should usually plant pulse crops (beans, peas, and fava beans) that nourish the soil. After pulses, you should try to plant root vegetables (beets, carrots, etc.).