Longman Dictionary of Contemporary English
Wiktionary
n. (context agriculture English) A farming practice in which the same land is used to grow different crops in successive seasons or years (when once the land would have been left fallow); used to prevent erosion and increase fertility.
Wikipedia
Crop rotation is the practice of growing a series of dissimilar or different types of crops in the same area in sequenced seasons. It is done so that the soil of farms is not used to only one type of nutrient. It helps in reducing soil erosion and increases soil fertility and crop yield.
Growing the same crop in the same place for many years in a row disproportionately depletes the soil of certain nutrients. With rotation, a crop that leaches the soil of one kind of nutrient is followed during the next growing season by a dissimilar crop that returns that nutrient to the soil or draws a different ratio of nutrients. In addition, crop rotation mitigates the buildup of pathogens and pests that often occurs when one species is continuously cropped, and can also improve soil structure and fertility by increasing biomass from varied root structures.
Crop rotation is used in both conventional and organic farming systems.