CROP-ROTATION

Crop rotation has been used for thousands of years. During the 1950s and early 1960s, it was felt that synthetic fertilizers and pesticides could forever replace crop rotation without loss of yield, but that opinion has changed. The current consensus is that crop rotation increases yield and profit and allows for sustained production. For example, maize, in a 2-year rotation with soybean, yields 5 to 20% more than continuous maize, and no amount of fertilizer or pesticide can compensate completely for that difference. It is not well understood what causes the rotation effect, but improvements in soil physical properties and soil organic matter probably play a beneficial role in rotations that include multiple years of sod, pasture, or hay. Short rotations such as maize-soybean actually result in a degradation in those same factors, yet the rotation effect still is realized. Recent information suggests that soilborne pathogens may be responsible for the yield depression seen with continuous monoculture.