Each year, these crops are rotated from one area to another in a regular pattern. These crop rotations help maintain soil fertility, and minimize insect pests and plant diseases.
Growing the same crop in the same soil year after year is an invitation to create depleted soil, and encourages pest and diseases to become established.
Crop rotation helps maintain soil fertility by moving heavy feeders to a different section each year, so soil can rest and rebuild between rotation cycles.
Crop rotations also help manage insect pests. Nearly all vegetables have insect pests that burrow in the ground and over-winter. When an insect pest emerges in the next spring, it is in a different crop. This eliminates its food source and reduces pest problems.
Rotations also help with weeds. Large-leaved vegetables like squash and corn form a canopy over soil which prevents sunlight from reaching the grounds in that area. Smaller, more vulnerable crops can then grow in that section, that has been naturally de-weeded by the larger crops, during the following growing year.