Since the Middle Ages, world agriculture has developed many crop-rotation plan possibilities, including three-year rotations with fallow land. These practices are part of so-called "agro-ecological" practices. Crop sequencing has numerous advantages. It is carefully prepared to suit the soil and climate. The type of cropping method is taken into account (conventional, organic, minimum cultivation, or direct seeding), as well as market prices for commodities and the emergence of new opportunities. Example rotations.
Simple crop rotation with 2 or 3 crops
In cereal-growing regions, crop sequencing is often fairly simple, with two or three crops sown, or even monoculture (one crop). This is ideal for high-yield, high-profit cereal crops. Typically, a sequence of soya – maize (one or two years in a row) is found in the grain-growing plains of the American Midwest and the Great Plains of central US. Cereals like wheat are sown when conditions are more limiting (i.e., when irrigation is not possible). In France, farmers often combine rapeseed - wheat – barley, or wheat - maize. On livestock farms, it is common to include temporary grassland or fallow.
The agronomic benefits of longer rotations: why and which crops?
Diversifying and lengthening the rotation means farmers can balance the financial risks and obtain a more stable income. Sowing a perennial crop is possible in livestock systems, or if a market exists, such as dehydration, with a rotation of maize - soya - maize - soya - maize - soya - alfalfa*4, for example. The root system of the crop improves the structure of the soil deep down. This rotation also makes it possible to spread manure at suitable times to improve soil fertility.
With rapeseed - wheat - barley rotations, the cycle can be lengthened to 6 years as follows: rapeseed - winter wheat - spring barley - maize - winter wheat - spring pea, with crop diversification. Spring crops reduce the TFI (treatment frequency index). Legumes improve soil fertility and structure. If there are industrial market opportunities, the rotation can be extended with other crops such as beet or potatoes.
Examples of crop rotations in conservation agriculture
Rotations are one of the pillars of soil conservation agriculture. Weeds, diseases, and pests can be managed easily with fewer treatments. Examples alternate dicots with monocots, and summer and winter crops. Possible plant types and associations are:
- soya or pea - rapeseed - wheat - maize
- wheat - maize - chickpea
- winter wheat - spring wheat - maize - sunflower
- spring barley - winter barley - spring pea - winter soft wheat - grain corn or silage
In soil conservation agriculture, farmers use cover crops or green manures, particularly leguminous cover crops. They play a role in weed control, preventing soil erosion, providing organic matter, and increasing soil fertility. They can be sown between two crops, or even used as permanent soil cover (associated or secondary crops).
The benefits of crop rotation in organic farming
In organic farming, certain multi-year forage crops are used (grasses or legumes such as alfalfa or red clover). They improve nitrogen fixing, weed control, and soil structure. Crop turnaround is every 7 to 12 years. In cereal cropping systems, crop rotation plans are 3 to 6 years, with annual crops only. Intercrops and crop mixes are frequently used. Here are a few examples:
- alfalfa *3 - wheat - mixed cereals and protein crops - wheat - triticale
- alfalfa *2 - wheat - triticale - spring bean - wheat - spelt - maize
- alfalfa *3 - wheat - wheat - sunflower - wheat - rye - clover - wheat - wheat - triticale.
Without multi-annual crops, farmers alternate crops depending on the species :
- maize - soya - wheat
- field bean - wheat - triticale - maize
- soya - wheat - triticale - spelt.