The effect of nitrogen application on yield stability of maize||soybean intercropping systems

Intercropping can improve yield and yield stability of crop, however, there are few studies on the yield stability of maize||soybean intercropping and the effect of nitrogen application on yield stability. A field experiment was conducted in Zhangye city, Gansu Province, in China, from 2018 to 2021, including two nitrogen rates (N0 and 300 kg·hm⁻²) and three planting patterns maize||soybean intercropping (M||S), monoculture soybean (MS), and monoculture maize (MM). Crop yields in monoculture and intercropping were determined, the productivity, land equivalent ratio (LER), partial land equivalent ratio (pLER), overyielding (OY), yield stability (YS), and nitrogen agronomy efficiency (NAE) were calculated. These indices were analyzed by comparison between monoculture and intercropping in order to clarify the effect of nitrogen on yield and yield stability of the maize||soybean intercropping. The results showed that the M||S intercropping had yield advantage, compared with the monoculture, the LER value under N0 and N300 on average over four years were 1.26 and 1.17, respectively, and the LER value was decreased that the LER value with N300 was lower than that of the N0 (P<0.05); all the partial land equivalent ratios (pLER_m) for maize with both N0 and N300 were greater than 0.5, and the partial land equivalent ratios (pLER_s) for soybean under N0 were greater than 0.5 and lower than 0.5 under N300; overyielding of intercropped maize under N0 and N300 were 36.88% and 36.88%, respectively, and overyielding of intercropped soybean under N0 and N300 were 14.77% and −30.46%, respectively; Nitrogen application could improve the yield stability, the yield stability of N300 treatment was 112.7 % higher than that of N0 (P<0.05), and the yield stability of monoculture system was 40.1 % higher than that of intercropping system (P<0.05). There was not a significant difference between the yield stability of nitrogen treatments under both intercropping and monoculture systems, In intercropping, the yield stability of intercropping maize in N300 treatment was significantly 178.6 % higher than that in N0 (P<0.05), nitrogen had no significant effect on the yield stability of soybean, in monoculture, the yield stability of monoculture soybean in N300 was significantly 139.3 % higher than that in N0 (P<0.05), and nitrogen application had no significant effect on the yield stability of monoculture maize; The NAE of intercropping was 76.7 % higher than that of monoculture (P<0.05). In summary, the main contributor to the yield advantage is maize in the maize||soybean intercropping system in Zhangye area of Gansu Province. Nitrogen improve the yield and yield stability of intercropping maize, reduces intercropping soybean yield, and does not affect intercropping soybean yield stability.