Differences in maize physiological characteristics, nitrogen accumulation, and yield under different cropping patterns and nitrogen levels

Intercropping and N fertilization play an important role in increasing crop yield. In order to further understand the advantage mechanism of intercropping and the effect of increasing N application on the advantage effect of intercropped crop, a field experiment was conducted to investigate the effects of different cropping patterns (i.e. M, maize monoculture; I1, maize-cotton intercrop; I2, maize-soybean intercrop) and N fertilization levels (N1, 100 kg ha-1; N2, 200 kg ha-1; N3, 300 kg ha-1; N4, 400 kg ha-1) on maize (Zea mays L.) Results showed that intercropping and increasing N application could enhance green leaf area per maize plant and chlorophyll content, and differences in green leaf area per plant and chlorophyll content between intercropping and monoculture under N1 were significant. Intercropping and increasing N application could improve maize photosynthetic characters, but their effects would be decreased with increasing N fertilization level. Root bleeding sap rate and root DM of maize were also obviously affected by intercropping and N fertilization, and the differences in root bleeding sap rate and root DM between I2 and M under N1 and N2 were significant. Compared to M, under N1, N2, N3, and N4, I2 increased grain N content by 12.8%, 6.3%, 2.7%, 1.5%, respectively. Intercropping and increasing N application could increase maize yield, and the difference in yield between I2 and M under N1 was significant. All the findings suggest that intercropping and increasing N application can improve maize physiological characters and increase maize root DM, N accumulation and yield, but their effects will be decreased with increasing N fertilization level.