Redefining soybean critical period for yield determination

Context: Critical period for yield determination is essential for crop management. Research on soybean has focused on grain number sensitivity to stress, while the impact of weight per grain remains underexplored. Objective: Redefine soybean yield determination by accounting for grain number and weight per grain. Methods: Three field experiments that imposed shading treatments at different growth stages. Crop development, yield, and yield components were monitored. Results: Critical period for yield determination extended from R4 to R7 stages, with peak sensitivity around R5.5. Grain number sensitivity lasted from R3 to R6, while weight per grain sensitivity occurred from R5 to R7. Compensation between yield components up to R4 occurred. Source-sink ratio accounted for most of the variation in weight per grain, which showed no significant deviation from this relationship across all treatments. Discussion: Critical period for soybean yield determination was identified, emphasizing the need to consider both grain number and weight per grain. Early compensation between yield components indicated a source limitation state in non-stressed crops. Additionally, no evidence of a sink limitation on yield within the range of stresses imposed was found. Conclusions: The critical period for soybean yield encompassed R4 to R7, with differential sensitivity to stress between grain number and weight per grain. Sink limitation did not directly cause yield reduction under the conditions studied. Yield optimization should focus on addressing source limitation during those growth stages. Implications: Provided valuable insights on soybean management, modeling and breeding. Orientate the focus on enhancing source capacity during critical stages.