Crop rotation is the practice of growing a series of dissimilar/different types of crops in the same area in sequential seasons.

Crop rotation gives various benefits to the soil. A traditional element of crop rotation is the replenishment of nitrogen through the use of green manure in sequence with cereals and other crops. Crop rotation also mitigates the build-up of pathogens and pests that often occurs when one species is continuously cropped, and can also improve soil structure and fertility by alternating deep-rooted and shallow-rooted plants.

Crop rotation is one component of polyculture.

Rationale

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: for example, rice followed by cotton.

Choice of crops

The choice and sequence of rotation crops depends on the nature of the soil, the climate, and precipitation which together determine the type of plants that may be cultivated. Other important aspects of farming such as crop marketing and economic variables must also be considered when deciding crop rotations.

Crop rotations may include two to six or more crop rotations over numerous seasons. A two crop rotation such as corn and soybean in cash grains or corn and alfalfa in forage systems use legumes to help fix nitrogen in the soil for utilization over the long term. Multiple cropping systems, such as intercropping or companion planting, offer more diversity and complexity within the same season or rotation. Carrots can be shaded by tomatoes and loosen soil below them. Double cropping is common where two crops, typically of different species, are grown sequentially in the same growing season. Winter rye and barley can be sown after oats or rice and harvested before the next crop goes in of oats or rice. These systems can maximize benefits of the rotation as well as available land resources.

More complex rotations commonly utilize people for greater use of on-farm nutrient management and additional farm products. A soil-feeding crop of clover could be replaced or aided by an application of manure to set up a field for a double crop of winter grains after potatoes. Soil building and pest population management benefits can be further utilized with different complexities of crop rotation. In general the complexity of a field’s rotation is limited by what soil, climate, and other environmental conditions permit. This also includes the current or desired management tools and goals of the farmer.

Source: Wikipedia