The severity and yield effects of the chocolate spot disease in faba bean affected by intercropping and nitrogen input

Background: The aim is to study the disease suppression efficiency, yield loss rate, and yield benefits of intercropped faba bean against chocolate spot under nitrogen (N) input, to clarify the effectiveness of intercropping faba beans in controlling chocolate spot and its contribution to yield increase. Results: Four N input levels and disease suppression treatments were discovered when faba bean-wheat intercropped was used. Adding N enhanced the chocolate spot's area under disease progression curve (AUDPC) by 27.1-69.9%. In contrast to monoculture, intercropping reduced the AUDPC of the chocolate spot by 32.4-51.0% (P < 0.05). Interestingly, the relative control efficacy (RCE) of intercropping at the EShan site was better. With disease suppression or non-suppression, N input increased grain yield loss and its components in faba bean. The total yield advantage effect (TE) and disease-suppression effect (DSE) of faba bean intercropped at the two experimental sites were significantly increased under N input (N-1 and N-2 level). The proportion of recovery yield due to intercropping suppressed disease (DSE/TE ratio) in EShan (52.1%) was higher than that in Xundian (40.9%), and the DSE of intercropping played an indispensable role in the two sites. Regression analysis of AUDPC and grain yield loss amount showed that one unit increase in chocolate spot AUDPC could cause a grain yield loss of 0.38-0.86 kg ha(-1). The partial land equivalent ratio (pLER) of intercropping faba beans at the EShan site was > 0.33. Conclusion: In conclusion, intercropped faba bean with N treatment (45-90 kg ha(-1)) was the best choice for maximizing the intercropping disease control effect. (c) 2023 Society of Chemical Industry.