Diversification of crop rotations

There are many agro-environmental and economic climatic benefits from the diversification of rotations. Already in 2012, the French Ministry of Agriculture (CEP) offered a summary on the subject. The diversification of rotations is described as one of the main levers of action for designing systems of crops that are economical in agricultural inputs (fertilizers, phytosanitary products). The diversification of rotations makes it possible to go further than optimizing the doses and active ingredients applied, and reduce the use of inputs at the farm level:

• by preventing weed flora from specializing, a variety of rotations can break weed cycles and reduce the use of herbicides;
• alternating host and non-host plants for crop pests decreases the risk of phytosanitary problems, thereby reducing the use of insecticides and fungicides;
• the introduction of legumes into crop successions fixes nitrogen in the air and enhances the positive effect of the legume on the next crop, in order to reduce the supply of synthetic nitrogen fertilizers.

By reducing the use of agricultural inputs, the diversification of crop rotation could therefore help to reduce the risks of diffuse pollution (water pollution by pesticides, eutrophication, etc.) and the emission of greenhouse gases.

Then, the diversification of crop rotation is described as a lever that can participate in better risk management at the farm level:

• the reduction in operating expenses related to input purchases can allow an improvement in the economic balance sheet of the operation (improvement in gross margins in a context of rising input prices);
• less use of plant protection products and synthetic fertilizers, as well as increased production of protein-rich forages through the introduction of legumes, can increase farm autonomy and make it less sensitive to variations in input prices;
• the cultivation of a diversity of species makes it possible to spread the peaks of work over the growing season;
• the diversification of rotations is a means of varying incomes, spreading the risks in the face of climatic and economic vagaries and thus increasing the resilience of farms in a context of uncertainty (volatility of agricultural prices, climate change).

Source: La diversification des assolements en France : intérêts, freins et enjeux – CEP – Analyse N° : 51 – Août 2012

Associated crops

Association is an essential agronomic principle in the system: alternate botanical families and / or associate them to benefit from each other's complementarities. Generally, 2 to 4 species are always associated. The choice of mixtures is very variable depending on the plots, the quality of the soil and the climatic conditions. The establishment of associated crops requires mastery of agroecological knowledge:

• The cereals / legumes association is beneficial in more than one way: the legume does not compete with its height for the cereal, it covers the soil and fixes atmospheric nitrogen (importance of the choice of varieties);
• Sowing density of cereal / legume mixtures (farm seed): The main crops are sown at the same density as in pure cultivation and the associated plants are sown at half their dosage in pure.
• Priority for the constitution of mixtures is given to locally adapted species. A mixture is designed according to the initially intended destination of each crop (mixture sold together or separately), its ease of sorting after harvest (size of the seeds of the mixture) and the maturity of the seeds. It must also take into account the height of each species to avoid excessive competition.

Figure: Example of associated crops in the South West of France - wheat faba bean

Source : https://osez-agroecologie.org

Manual AgriAdapt : 5 case studies of arable crops farms in Spain, Germany, France and Estonia.