Critical Periods for Waterlogging Effects on Yield and Grain Components in Sunflower (<i>Helianthus annuus</i>), Soybean (<i>Glycine max</i>) and Sorghum (<i>Sorghum bicolor</i>): A Comparative Study

ABSTRACT Waterlogging affects a high proportion of cultivated land worldwide. Sunflower, soybean and sorghum growth and yield can be affected differently depending on the moment and duration of waterlogging stress. If stress conditions occur during the critical period for yield potential definition (flowering in, sunflower and sorghum and end of pod formation in soybean) they directly reduce grain number, but if the stress occurs during the grain‐filling period, grain weight would be affected. The aim of this study focuses on determining the effects of the moment and duration of waterlogging stress on the yield and its components in sunflower, soybean and sorghum. This information will be useful to understand the effects of waterlogging on yield and to choose a suitable crop or sowing date based on predicted weather conditions for a certain place. To achieve this objective, four experiments were conducted at the Experimental Station of INTA (Reconquista, Santa Fe, Argentina). The effect of the waterlogging in terms of moment (vegetative, critical and grain‐filling periods) and duration (3, 7 and 10 days) on the three crops was evaluated. Sunflower expressed the most negative impact of waterlogging during the vegetative stages (26, 78 and 98% of yield losses with 3, 7 and 10 days, respectively) while soybean suffered major reductions when the stress occurred during the critical period (5%–17% of yield loses). Sorghum did not express any negative responses for the moments and durations tested. This study suggests that the critical period for a waterlogging event differs, according to crops, from the critical period cited for other stresses. Moreover, the magnitude of the damage will mainly depend on the duration of the event. Further studies are needed to elucidate different physiological responses of the species during waterlogging stress.