Agronomic and economic benefits of maize–legume intercropping under reduced fertilizer levels in Nepal

Continuous maize monocropping with insufficient nutrient inputs in Nepal has depleted soil fertility, and reduced productivity and farm incomes. Integrating legumes into maize systems can reverse these trends, offering a sustainable pathway to agricultural intensification. In 2024, 41 large-scale multi-location trials (0.12 ha each) were conducted across six tropical Terai districts under CIMMYTs Maize Commercialization Model (MCM) using randomized complete block design to compare intercropping and monocropping systems. The experiment included eight treatments: four maize–legume intercrops (maize-mungbean [2:3] and maize-cowpea [2:2] at recommended and 34% reduced fertilizer rates applied on an equivalent area basis), three sole crops (maize, mungbean, cowpea), and a conventional farmer’s practice (FP). All intercropping systems, with both full and reduced fertilizer levels, produced maize yields (8.7 t ha −1 ) comparable to maize monocropping (8.6 t ha −1 ) and 40% higher than the FP (6.2 t ha −1 ), likely due to, improved resource- and nutrient-use efficiency, improved management practices and lower nutrient demand under reduced maize area in intercropping. The land equivalent ratio (LER) ranged from 1.6 to 2.6, while gross margins increased by 91% in maize-mungbean and 324% in maize-cowpea systems relative to maize monocropping. The highest benefit-cost (B:C) ratio and marginal rate of return (MRR) were observed for maize-cowpea intercropping and was strongly preferred by farmers for its ease management, higher productivity, and profitability. These results highlight the potential to scale intercropping through the MCM, reducing fertilizer use by 34% while enhancing yield, land productivity, and farm income under Nepal’s chronic fertilizer shortages.