| Summary: | Silicon (Si) application is known to enhance plant resistance to diverse pathogens. Therefore, a greenhouse study was conducted to determine whether Si reduces red crown rot (RCR) of soybean caused by the soil-borne fungal pathogen <i>Calonectria ilicicola</i>. The soybean cultivar Enrei was grown in soil mixed with different concentrations of sodium silicate (Na<sub>2</sub>SiO<sub>3</sub>) and inoculated with <i>C. ilicicola</i> (1% <i>w</i>/<i>v</i>). Si application significantly reduced RCR severity and relative fungal growth in the roots, as per qPCR, at both sampling time points. Notably, the shoot Si content correlated significantly with RCR severity in the roots. In addition, Si application reduced the accumulation of malondialdehyde, indicating that the maintenance of cellular membrane integrity is an important mechanism underlying Si-mediated protection of soybean plants from RCR. Furthermore, Si-treated plants exhibited improved water and nitrogen uptake and root and shoot growth. Aboveground biomass and seed yield at harvest increased with increasing Si concentration (0.0–3.0 g Na<sub>2</sub>SiO<sub>3</sub> kg<sup>−1</sup> soil). However, further increase in Si concentration (6.0 g Na<sub>2</sub>SiO<sub>3</sub> kg<sup>−1</sup> soil) reduced seed yield. Therefore, Si treatment can be used as an effective strategy to control RCR in soybean.
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