Cereal-legume intercropping: a smart review using topic modelling

Abstract

IntroductionOver the last decade, there has been a growing interest in cereal-legume intercropping for sustainable agriculture. As a result numerous papers, including reviews, focus on this topic. Screening this large amount of papers, to identify knowledge gaps and future research opportunities, manually, would be a complex and time consuming task.Materials and methodsBibliometric analysis combined with text mining and topic modelling, to automatically find topics and to derive a representation of intercropping papers as a potential solution to reduce the workload was tested. Both common (e.g. wheat and soybean) as well as underutilized crops (e.g. buckwheat, lupin, triticale) were the focus of this study. The corpus used for the analysis was retrieved from Web of Science and Scopus on 5th September 2022 and consisted of 4,732 papers.ResultsThe number of papers on cereal-legume intercropping increased in recent years, with most studies being located in China. Literature mainly dealt with the cereals maize and wheat and the legume soybean whereas buckwheat and lupin received little attention from academic researchers. These underutilized crops are certainly interesting to be used as intercropping partners, however, additional research on optimization of management and cultivar’s choice is important. Yield and nitrogen fixation are the most commonly studied traits in cereal-legume intercropping. Last decade, there is an increasing interest in climate resilience, sustainability and biodiversity. Also the term “ecosystem services” came into play, but still with a low frequency. The regulating services and provisioning services seem to be the most studied, in contrast terms related to potential cultural services were not encountered.DiscussionIn conclusion, based on this review several research opportunities were identified. Minor crops like lupin and buckwheat need to be evaluated for their role as intercropping partners. The interaction between species based on e.g. root exudates needs to be further unraveled. Also diseases, pests and weeds in relation to intercropping deserve more attention and finally more in-depth research on the additional benefits/ecosystem services associated with intercropping systems is necessary.

Harnessing monocrop breeding strategies for intercrops

“…Previous studies demonstrate that mixed crops frequently yield higher in low nitrogen fertilization conditions and more consistent returns per unit area, improve diets and produce greater returns than pure stands particularly when legumes are involved (Cordero and McCollum, 1976;Francis and Sanders, 1978;Willey, 1979;Francis, 1981;Beets, 1982;Pearce and Edmondson, 1984;Li et al, 2023;Landschoot et al, 2024;Zustovi et al, 2024). The results vary when nitrogen fertilization is introduced as the availability of nitrogen influences both the productivity and the cooperative interactions between cereal and legume crops (Jensen, 1996;Ghanbari-Bonjar and Lee, 2002;Andersen et al, 2005;Hauggaard-Nielsen and Jensen, 2005;Kebede, 2021;Weih et al, 2021).…”