Crop rotation—growing different crops in succession in the same field—is one of the most powerful techniques of sustainable agriculture, and avoids the unintended consequences of putting the same plants in the same soil year after year. It is a key element of the permanent and effective solution to pest problems because many pests have preferences for specific crops, and continuous growth of the same crop guarantees them a steady food supply, so that populations increase. For example, right now European corn borers are often a significant pest in the United States because most corn is grown in continuous cultivation or in two-year rotations with soybeans. Four- or five-year rotations would control not only corn borers, but many other corn pests as well. In fact, rotation reduces pest pressure on all the crops in the rotation by breaking the pest reproductive cycles.
In rotations, farmers can also plant crops, like soybeans and other legumes, that replenish plant nutrients, thereby reducing the need for chemical fertilizers. For instance, corn grown in a field previously used to grow soybeans needs less added nitrogen to produce high yields.
On a related note, the importance of crop rotation as a defense against pest infestations should be a key part of any discussion about growing crops for bioenergy purposes. Government policies to encourage bioenergy crops should not inadvertently encourage farmers to forgo crop rotation in favor of planting corn year after year.
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