The shift from crop rotation to monoculture is one of the main causes of soil erosion. A corn-wheat-grass rotation has an erosion rate of 6.7 Tn/ha/year compared to 50 Tn/ha/year for a continuous corn crop. Because of these erosion rates, the loss of soil fertility is evident, increasing the dependence on inputs to cover this decline in fertility. Normally, these inputs are not composted organic matter but chemical fertilizers that can also destructure the soil, in addition to other collateral effects.
Crop rotation is the repeated establishment of an orderly succession of crop species on the same plot. It is the opposite of monoculture, or growing the same crop on the same plot over time.
If rotation is the orderly succession of crops that are repeated over a number of years, the alternative is the simultaneous cultivation of the species involved in the rotation. In this case, the farm is divided into different plots, each of which is devoted to a different crop each year, until the rotation is complete. These plots are called “alternative leaves” or “amelgas”.