Foliar Silicon Sources Affect Silicon Accumulation in Tissues and Yield of Soybean Under Subtropical Conditions in Southern Brazil

Silicon fertilization has been reported to improve crop performance under different environmental conditions; however, information regarding the efficiency of different foliar silicon sources under subtropical field conditions remains limited, particularly for soybean. This study evaluated the effects of different foliar silicon sources on silicon accumulation in leaves and seeds and their association with soybean yield under subtropical conditions in southern Brazil. A field experiment was conducted using five treatments consisting of different silicon sources applied during the reproductive stage. Silicon concentrations in leaves and seeds and seed yield were determined, and Pearson’s correlation analysis was performed to investigate the relationships among these variables. Foliar silicon accumulation differed according to the fertilizer source, with potassium silicate resulting in the greatest silicon concentration in leaves, whereas silicon oxide promoted the highest silicon accumulation in seeds. Silicon-containing thermophosphate was associated with the highest seed yield; however, because this fertilizer also supplied nutrients other than silicon, this response cannot be attributed exclusively to silicon. Significant positive correlations were observed between silicon accumulation and seed yield, particularly for seed silicon concentration. Overall, the results indicate that the agronomic efficiency of foliar silicon fertilization depends on the fertilizer source, with different formulations exhibiting distinct responses for silicon accumulation and productivity. These findings provide useful information for selecting foliar silicon fertilizers according to specific agronomic objectives, since no single silicon source simultaneously maximized foliar silicon accumulation, seed silicon concentration, and seed yield.