Crop rotation is a systematic approach to deciding which crop to plant where in your vegetable garden from one year to the next. It is as important a factor in soil health as amendments, and reduces the amount of work you have to put into achieving healthy soil for your plants.
Interesting fact: George Washington Carver was a major pioneer in teaching of crop rotation, a big help in replenishing soil, rejuvenating the yields and success in farming.
Different crops have different nutrient requirements and affect soil balance differently. Some, like corn and tomatoes, are heavy feeders that quickly deplete soil nitrogen and phosphorus. Thus, if you plant corn in the same spot year after year that plot of soil will run low on nitrogen and phosphorus more quickly than other parts of your garden will. By changing the location of corn each year, you’ll be able to renew the plot where it grew the preceding year, so your soil won’t get out of balance.
Following up with nitrogen fixing plants, like beans or peas, in an area which had heavy feeders the year before replenishes the soil.
The other benefit of crop rotation is reduction of diseases and pests.
Plan your rotation by plant families, because pests and diseases will usually affect all members of the same family. For example, Colorado potato beetles like to eat potato plants, but they also enjoy feasting on tomato leaves and eggplant foliage. Since these beetles overwinter in the soil, if you plant eggplant in a spot where you grew potatoes the year before, you could be inviting a beetle problem for your eggplants from the day they’re planted. Likewise, several serious bacterial and fungal diseases overwinter in plant debris in the soil.
Don’t forget, crop rotation is part of building healthy soil which is an ongoing process, one to work at each garden season.