Identifying the research gaps in cereal-grain legume intercropping

Environmental stressors including rapid declines in crop pollinators and predators, intense periods of drought and flood, elevated greenhouse gas emissions and global temperature are an ever-increasing threat to efficient agricultural production and food security while agricultural intensification endangers soil health, fertility and agrobiodiversity. Intercropping (IC) cereal crops such as wheat, barley, triticale and maize with legumes including field bean, pea, lentil and lupin offers an agroecological solution to improve sustainability and environmental impacts while contributing to Net Zero targets. IC is growing two or more species simultaneously on a piece of land to maximise land use and biological resource potential. Europe is currently a net importer of protein for human and animal supply chains and recent research on IC cereal-grain legumes, carried out as part of the ReMIX project, has shown the potential for IC to meet increasing market demand for regional protein and improve farm efficiency by reducing inputs such as agrochemicals. Results confirm stabilised yields in organic agriculture and reduced synthetic input use in conventional agriculture. Compared to their respective monocultures, IC improved cereal grain quality and protein concentration in unfertilised crops secondary to enhanced rates of atmospheric nitrogen fixation (Bedoussac et al., 2015). Greater utilisation of resources enabled IC advantages to extend to weed, pest and disease management with trials showing disease could be reduced by up to 40% compared to sole crops (Hauggaard-Nielsen et al., 2007). The purpose of this research which was based on literature was to explore the focus of the work that has been carried out in Europe on intercrops, and the linkages between the research topics and the research groups.
A literature search was carried out based on keywords and carried out in Scopus.
The search was constrained to European countries. Connections between keywords and groups of researchers were explored using the VOSViewer, a bibliometric analysis tool. This will help identify areas which warrant further IC research.
The analysis highlighted greater understanding of crop production and cultivation methods are required including basic agronomy to provide technical notes to farmers. This includes establishment using minimum tillage methods, optimal seed rates and varieties. Harvest methods, processing facilities and market demand for intercrops harvested simultaneously are still in their infancy. The method of action within specific plant-plant interactions, crop combinations for optimal nutrient translocation, thermal and hydrological resource use, increased opportunities for pollinators and weed and pest control are not well established. It is vital that changes in above and below ground biodiversity should be included in future research.