Introducing soybean into maize fields improves responses of maize canopy and root architecture to light and water utilization under different irrigation levels

Backgrounds

Maize monoculture often leads to suboptimal light and water utilization, restricting productivity. Intercropping with soybean may enhance maize canopy and root traits, but its effectiveness under different irrigation levels remains unclear.

Methods

A two-year randomized block field trial was conducted in Northwestern China, with traditional maize monoculture as the control and maize/soybean intercropping systems introduced. Three irrigation levels (60%, 80%, and 100% of crop evapotranspiration) were set to evaluate maize productivity, canopy and root architecture, and light and water use efficiency under both monoculture and intercropping systems.

Result

Results showed that intercropping increased cob length, cob diameter, and 100-grain weight of maize compared to monoculture, economic income of intercropping increased by 7.97% and 17.29% in 2023 and 2024, respectively. The intercropping improved the leaf angle and leaf area index of maize, while also promoting lateral root expansion of maize, leading to greater root dry weight and root length compared to monoculture, especially within the 0–20 cm soil layer. The intercropping enhanced the efficient utilization of light and water resources of maize, as evidenced by higher net photosynthetic rates and maximum photosynthetic quantum efficiency compared to monoculture, as well as greater water productivity. In addition, with increasing irrigation levels, improvements in the canopy, root, and light utilization of maize increased for both monoculture and intercropping, however, total water productivity exhibited a decreasing trend, particularly in intercropping.

Conclusions

IMS combined with moderate irrigation (80% of crop evapotranspiration) optimized canopy and root coordination, enhancing both light and water use efficiency.