How maize-legume intercropping and rotation contribute to food security and environmental sustainability

Hunger continues to be a pervasive problem throughout the world, with 193 million individuals across 53 countries/territories experiencing profound food insecurity (UN, 2022), and the situation is expected to be intensified by the increasing global population. In order to meet the urgent demand for calories and nutrients, agricultural production will need to increase by 70% or more (FAO, 2018). The Asian green revolution as an innovation of intensive agriculture has trebled grain yields, but brought soil degradation, increased risk of pest and disease outbreaks, and environmental pollution since it increased the application of fertilizer, pesticide, irrigation and agricultural machinery (Snapp et al., 2010). Future agriculture is expected to address simultaneously several intertwined challenges through increased productivity, reduced environmental impact and enhancement in climate change adaptation and mitigation (Raseduzzaman and Jensen, 2017; Wei et al., 2023). Crop rotation (temporal diversification) and intercropping (spatial diversification) strategies have been proven to improve agricultural sustainability (Li et al., 2021a, Li et al., 2021b), providing a tradeoff between crop productivity and other ecosystem services (Rockström et al., 2017; Martin-Guay et al., 2018; Mingotte et al., 2021).

Globally, maize is grown in a large area (197.23 Mha), accounting for 30% of the food supply in the Americas, 38% in Africa and 6.5% in Asia, and is a major contributor to local food security (Prasanna et al., 2020; Tripathi et al., 2021). Besides being a major source of food and feed for humans and animals, it is also a potential source of bioenergy (Erickson and Berger, 2013). Additionally, legumes are rich source of protein and has a high market value (Ainsworth et al., 2012; Chimonyo et al., 2019). Global demand for legumes, especially soybeans, has exploded in recent decades due to their use as a feedstock for soy–animal feed, biofuels and vegetable oil (Ritchie et al., 2023). In order to meet production needs, land expansion for soybean production has increased by 160% in Brazil and 57% in Argentina, and much of this expansion has come at the cost of deforestation. By 2016, 9% of the continent’s forests were converted to soybeans (Song et al., 2021; Chen et al., 2022). Among the UN sustainable development goals (SDGs), mitigating climate change and biodiversity loss to achieve zero deforestation is prominent in the global supply chains of commodities such as palm oil and soybeans (Song et al., 2021).

The combination of intercropping and crop rotation of maize and legume has emerged as a promising agricultural practice that can improve yields and soil health while reducing the environmental impact of conventional farming practices. For example, the maize-soybean intercropping-rotation model in China can achieve maize yields comparable to those of monoculture maize system while additionally harvesting a season of soybeans, with an experimental land-equivalent ratio of 1.4 (Du et al., 2018). As a result, intercropping and rotation of crops have received a lot of attention in scientific and technological circles and are also promoted by the Central No.1 document of China in 2022 (State Council of CPC, 2022).

The objective of this study is to improve our understanding of how different historical breakthroughs in agriculture such as the Green Revolution etc. have influenced the research efforts on maize-legume intercropping and crop rotation, and whether the most traditional cropping systems align with the world’s need for future sustainable agriculture. For this purpose, we use bibliometric analysis to identify research hotspots, trends, and gaps in maize-legume intercropping and rotation over the past 30 years. We also provide a systematical comparison of the development history and patterns of intercropping and crop rotation systems. As a transition towards sustainable agriculture, our systematic mapping of promising cropping systems might be valuable for inspiring and informing countries and regions facing food and environmental insecurity, and consequently offers a possible direction for global sustainable development.