Waterlogging effects on soybean physiology and hyperspectral reflectance during the reproductive stage

Authors: ADEGOYE, GRACE - Mississippi State University; OLORUNWA, OMOLAYO - Mississippi State University; WALNE, CHARLES - Mississippi State University; WIJEWANDANA, CHATURIKA - Mississippi State University; ALSAJRI, FIRAS - Mississippi State University; KETHIREDDY, SWANTANTRA - Mississippi State University; Reddy, Krishna; REDDY, RAJA - Mississippi State University

Submitted to: Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/6/2023
Publication Date: 4/9/2023
Citation: Adegoye, G.A., Olorunwa, O.J., Walne, C.H., Wijewandana, C., Alsajri, F.A., Kethireddy, S.R., Reddy, K.N., Reddy, R.K. 2023. Waterlogging effects on soybean physiology and hyperspectral reflectance during the reproductive stage. Agriculture. 13(4):844. https://doi.org/10.3390/agriculture13040844.
DOI: https://doi.org/10.3390/agriculture13040844

Interpretive Summary: Waterlogging stress has been shown to significantly reduce seed yield by 40-80% in soybeans, depending on the growth stage, cultivar, waterlogging duration, and depth. However, the growth and physiological responses of soybean during the reproductive stage to waterlogging have not been comprehensively studied. Scientists from Mississippi State University, Mississippi State, Mississippi and USDA-ARS, Crop Production Systems Research Unit, Stoneville, Mississippi have investigated the effects of waterlogging and subsequent reoxygenation on the growth, physiology, yields, and leaf hyperspectral reflectance traits of soybean. The results showed that soil oxygen levels declined rapidly to zero in about 5 days after waterlogging and slowly recovered in about 5-16 days. However, it did not reach the same level as the control plants, which maintained an oxygen concentration of 18%. Increasing waterlogging duration negatively affected leaf chlorophyll index, water potential, and stomatal conductance, with a consequent decline in the photosynthetic rate. Further, decreased photosynthetic rate, leaf area, and mineral nutrients resulted in lower biomass and seed yield. Waterlogged plants had higher reflectance in the PAR, blue, green, and red regions, respectively, and lower reflectance in the near-infrared, tissue, and water-band regions, indicating changes in chemistry and pigment content. Pod dry weight and leaf number were the most and least sensitive parameters to waterlogging. This study demonstrated that the soybean crop is susceptible to waterlogging during the reproductive stage. The growth, physiology, and hyperspectral reflectance data from this study could be used to develop improved cultivars to ensure the stability of soybean production in waterlogged-prone areas of the United States.

Technical Abstract: Waterlogging is a major limiting factor for soybean production, severely affecting growth and yield development during the reproductive stage. However, the growth and physiological responses of soybean during the reproductive stage to waterlogging have not been comprehensively studied. Here, we investigated the effects of waterlogging and subsequent reoxygenation on the growth, physiology, yields, and leaf hyperspectral reflectance traits of a soybean cultivar. Asgrow AG5332 was grown to stage R1 in outdoor pot culture and waterlogged for 16 days. The flooded pots were drained and continuously monitored for recovery for an additional 16 days. The results showed that soil oxygen levels declined rapidly to zero in about 5 days after waterlogging and slowly recovered in about 5-16 days. However, it did not reach the same level as the control plants, which maintained an oxygen concentration of 18%. Increasing waterlogging duration negatively affected leaf chlorophyll index, water potential, and stomatal conductance, with a consequent decline in the photosynthetic rate. Further, decreased photosynthetic rate, leaf area, and mineral nutrients resulted in lower biomass and seed yield. Waterlogged plants had higher reflectance in the PAR, blue, green, and red regions, respectively, and lower reflectance in the near-infrared, tissue, and water-band regions, indicating changes in chemistry and pigment content. Pod dry weight and leaf number were the most and least sensitive parameters evaluated after 16 days of waterlogging, decreasing by 81% and 15%, respectively. The current study reveals that the soybean crop is susceptible to waterlogging during the reproductive stage due to poor recovery of soil oxygen levels and physiological parameters. Understanding and integrating the growth, physiology, and hyperspectral reflectance data from this study could be used to develop improved cultivars to ensure the stability of soybean production in waterlogged-prone areas of the United States.