Effects of nitrogen supply on defensive changes in maize against biotic stressors

The maize yield potential is constrained by a diverse range of biotic and abiotic factors, ultimately leading to di- minished crop yield, and quality. Nitrogen (N)-an indispensable fertilizer element is known to exert an influence on incidence and severity of these biotic stresses. This paper describes the effect of various levels of N application and contrasting maize genotypes on weed infestation, maydis leaf blight (MLB) and fall armyworm (FAW) inci- dence in maize. The field experiment was carried out at ICAR-Indian Agricultural Research Institute, New Delhi during two consecutive years (2021 and 2022). Treatments comprising 6 maize genotypes (PJHM 1, PC 4, DKC 9167, PMH 13, AH 4271 and Pusa Vivek QPM 9-I) and seven N levels (0, 40, 80, 120, 160, 200 and 240 kg N/ha) were arranged in a factorial randomized complete block design. Results showed that genotypes with profuse growth, greater leaf area and higher light interception (PJHM 1, DKC 9167 and PMH 13) had minimum weed inci- dence and may be considered as a key element of integrated weed management in smallholder agriculture. Dis- ease severity in PV QPM 9-I (5.3) was higher than all other genotypes while least in AH 4271 (2.7). The maximum and minimum pest incidence was observed in PJHM 1 (4.9 and 5.6,) and PV QPM 9-I (2.1 and 2.4), respectively. In general, the total (-9.4%) and broad-leaf weed density (-26.4%) reduced with increasing use of nitrogenous fer- tilizers, while the application of lower N rates reduced the prevalence of narrow-leaf weeds (34.2%). The early leaf senescence and poor photosynthetic rate at lower rates of N application decreased the plants immunity against MLB disease. Oppositely, the increased succulency at higher N doses led to severe FAW incidence in maize over control. Therefore, the study demonstrates that planting of competitive/resistant genotypes and use of 160 kg N/ha resulted in relatively less overall burden of biotic stressors on maize crop.