ABSTRACT
Grain legume-cereal intercropping systems L. Bedoussac, ENSFEA, INRA AGIR, France; E-P. Journet, CNRS LIPM, INRA AGIR, France; H. Hauggaard-Nielsen, Roskilde University, Denmark; C. Naudin and G. Corre Hellou, Ecole Supérieure d’Agricultures, France; E. S. Jensen, Swedish University of Agricultural Sciences, Sweden; and E. Justes, INRA AGIR, France1
1 Introduction
2 Effects on yields and quality
3 Agronomical performance of intercropping
4 Cultivation practices in intercropping
5 Future trends and conclusion
6 References
Intercropping involves simultaneously growing two or more crops in the same field for a significant period of time that could be the whole period of cultural season for some arable crops such as in cereal-legume intercrops (Willey 1979a; Vandermeer et al. 1998; Malézieux et al. 2008; Jensen et al. 2015). The practice is ancient as early records from many human societies all over the world have shown (Willey 1979a). According to Altieri (1999), intercropping systems are estimated to still provide as much as 15-20% of the world’s food supply. In Latin America farmers grow 70-90% of their beans with maize, potatoes and other crops, and maize is intercropped on 60% of the region’s maize-growing area (Francis, 1986). In rural sub-Saharan Africa, intercropping is considered as a traditional cropping system with the predominant crop combinations being maize, bean/cowpea and pumpkin (Matusso et al. 2014). Intercropping has also been practised in China for thousands of years and it has been estimated that intercropping surfaces are about 30 million ha representing 20-25% of the Chinese arable land (Li, 2001). The practice was widespread in some European farming systems up until the 1950s – before the so-called fossilisation of agriculture. At that time as much as 50% of all available nitrogen (N) may have originated from symbiotic N2 fixation by leguminous food, forage and green manure crops used in rotation which limited the reactive N received from fertiliser-N and then the negative impact
of NO3, NH3 and N2O on the environment (Peoples et al. 2009). In those systems, land was dedicated to fertility-generating legume rotations, which potentially also contributed to other ecosystem services such as carbon sequestration and biodiversity (Peoples et al. 2009). Despite these advantages, grain legume cropping is less favoured now, even in organic crop rotations, because of a reputation of low yield and instability related to several factors like intolerance to water stress, harvest difficulties because of lodging, pathogen attacks, sensitivity to insect pests and weed competition. Aiming at higher crop diversity, intercropping is an interesting option to introduce legumes in cropping systems in a more efficient way as compared to sole cropping rotations. Therefore, grain legumes were often grown in different cereal intercrop combinations to secure yield stability and soil fertility, lowering nutrient losses and reducing weeds, diseases and pests (Hauggaard-Nielsen et al. 2001b, 2007). This suggests that intercropping is a way to improve adaptability to climate change taking into account both biotic stresses (Padulosi et al. 2002) and abiotic stresses (e.g. of more and more unpredictable weather patterns (IAASTD 2009)). These intercrops were found all the more efficient and productive when grown in low-input systems, and in particular in organic farming (Bedoussac et al. 2015). Since the 1950s, intercropping declined in Europe and some other parts of the world in the post-war period due to the intensification of agriculture focusing on maximising yields of sole crops using external inputs (artificial fertilisers and pesticides) together with the optimisation of mechanical management (Crews and Peoples 2004; Anil et al. 1998; Malézieux et al. 2008).
