Assessing the Impact of Early-Season Waterlogging on the Nodule Activity and Nitrogen Fixation of Mungbean (Vigna radiata L.)

Abstract

Early-season waterlogging is a critical abiotic stress that adversely affects legume establishment and symbiotic nitrogen fixation, particularly in mungbean (Vigna radiata L.) grown under poorly drained conditions. This study evaluates the impact of early-season waterlogging on nodule activity and nitrogen fixation in mungbean under field conditions. Experimental treatments simulated varying durations of waterlogging during the early vegetative stage to assess their effects on root development, nodulation, and plant growth. Key parameters measured included nodule number, nodule dry weight, nitrogenase activity, plant biomass, chlorophyll content, and final grain yield. Results indicated that waterlogging significantly reduced nodule formation and impaired nitrogenase activity due to oxygen deficiency in the root zone, leading to decreased biological nitrogen fixation. Affected plants exhibited reduced root growth, lower chlorophyll content, and diminished biomass accumulation. The severity of impact increased with longer waterlogging duration, with prolonged stress causing substantial yield reduction. However, short-term waterlogging showed partial recovery once normal soil conditions were restored, indicating some resilience in mungbean. The study highlights the sensitivity of legume–rhizobium symbiosis to soil aeration and emphasizes the importance of proper drainage management. While analytical methods were used to assess physiological and biochemical responses, the primary focus remains on agronomic performance and crop productivity. These findings provide practical insights for farmers to adopt improved field drainage, select tolerant varieties, and adjust planting strategies to mitigate the adverse effects of waterlogging and sustain mungbean production in vulnerable environments.