Certain parts of the vegetable garden are ideal for certain types of vegetables. Wire fences are perfect for pole beans to climb. Corn belongs at the northern edge where it will not shade lower plants. Vegetable gardening would be simpler if it were like permanent landscaping. Instead, vegetable plants are seasonal and very consumptive. They prefer fresh resources. Garden rotation gives them more of what they crave.
Garden rotation, or crop rotation, is growing vegetables where they have not grown recently. For the most efficiently planned gardens, it happens seasonally. Alternatively, some types of vegetables might be happy to grow repeatedly in the same soil for a few years. Some vegetable plants are more consumptive than others. Some soils are more susceptible to nutrient depletion than others. A few variables are involved.
Furthermore, the various vegetable plants deplete distinct sets of nutrients. Conversely, they allow other nutrients to replenish. That is why garden rotation is so effective. For example, if beans grow in the same location for too long, they deplete their favorite nutrients. The nutrients that they use less of secretly replenish. Tomatoes or corn might appreciate the replenishment, without craving so much of what is deficient.
Eventually, vegetable plants can return to a location where they grew a few years earlier. Again, a few variables are involved. Some might return after an absence of only a single year. Consumptive plants, such as tomatoes and beans, should avoid a previously used location for three or more years. So should related vegetables. Peppers and eggplants are related to tomatoes, so should avoid the same used locations.
Garden rotation can also inhibit proliferation of some soil borne pathogens. In other regions, this is a more serious concern. Soil borne pathogens that infest mildly during their first year might flourish with the same host material during a second year. Garden rotation deprives them of that.