Description of the Business As Usual (BAU):
In annual crop systems, the period between two main crops is usually left without cropping. Fallow is the common system between two main cash crops. Furthermore, in conventional systems, harvest residues are removed by baling or buried by ploughing. Depending on the crop sequence and crop period, the gap between main crops can be more extended.
Description of the system change:
Cover crops are auxiliary crops that are planted to cover the soil rather than for the purpose of being harvested. They are established temporary between two main crops (cash crops) as alternative to fallow. Depending on the purpose and the specific function developed they are also called catch crop (absorbing CO2 and nutrients) or green manure (acting as nutrient source) the latter usually associated to legume species (Ramírez-García et al, 2015).
Cover crops are recommended when there is a gap of living crop for a long time, so there is much time between the harvest and the seeding of the following crop. This might reduce the protection capacity as residues would have been decomposing for long period decreasing the soil cover. The introduction of legumes is recommendable for their nitrogen fixation effect that could reduce the use of fertilizers for the main crop. Other species also act as storage for nutrients when lixiviation and erosion risks are higher, and they supply nutrients after termination (Blanco-Canqui et al., 2015). In temperate-humid regions, the most common cover crops include hairy vetch, red clover, and forage pea as legumes, rye, oat, and Italian ryegrass as grasses, and white mustard or forage radish as soil-structuring species, species from other families such as Boraginaceae are also used. Normally, functional mixtures of three or more species are used, combining soil protection, nitrogen fixation, and improvement of soil structure. These mixtures are well suited to autumn sowing after the main crop and can survive the winter in many areas of northern Europe.
Cover crops maintain a permanent soil cover while contribute to the system diversification and crop rotation. When the cover crop is established by direct seeding, it is fulfilling the regenerative agriculture principle of minimum soil disturbance, provided that the mowing is carried out by chemical control, mechanical (mower or roller-crimper) or grazing. The establishment of a cover crop helps control weeds by restricting light and nutrients supply. In fact, the use of cover crops is usual to prevent weeds in organic No till systems
Seeded under No till, the use of appropriate equipment and machinery is required, preferently after spreading the residue from the previous crop evenly. The straw mulch cover prevents the soil-seed contact, hindering and reducing weed germination.