Laurent Bedoussac, Étienne-Pascal Journet, Henrik Hauggaard-Nielsen, Christophe Naudin, Guénaëlle Corre-Hellou, Loïc Prieur, Erik Steen Jensen, Eric Justes

ENFA-INRA, UMR1248 AGIR, 2 route de Narbonne, CS 22687, 31326, Castanet-Tolosan, Cedex, France.

Abstract

Intercropping, i.e., simultaneously growing two (or more) species in the same field for a significant period of time but without necessarily concomitant sowing or harvest, is a practice aimed at eco-functional intensification.
This chapter integrates a comprehensive amount of original data from field experiments conducted since 2001 on spring and winter cereal-grain legume intercrops in experimental and farm contexts in France and Denmark, in an attempt to generalise the findings and draw up common guidelines. We have shown that intercrops appear to be a useful agronomic solution for organic arable cropping, particularly in low-N input systems, to enhance: (i) yields because of a general improvement of environmental resource use; (ii) cereal grain protein concentration due to a non-proportional competition for soil mineral N and other plant growth factors; and (iii) weed control compared to legume sole crops.
Therefore, intercropping can be a way to successfully produce organic grain legumes and cereals. However, it is difficult to propose generic crop technical protocols because of the multitude of production objectives and, hence, of combinations of species, varieties, densities, structure and manuring strategies.
Consequently, it should be emphasized that: (i) the species and varietal traits suited to intercropping and organic farming will make it necessary to reconsider the varietal selection criteria; (ii) further mechanistic understanding of the behaviour of intercropping systems is required to be integrated into crop models; and (iii) the development of intercrops cannot take place without the participation of all of the actors in the value chain because of lock-in mechanisms.