Effects of silicon supplementation on growth and silicon accumulation in tall fescue (Festuca arundinacea) and bentgrass (Agrostis stolonifera)

Previous studies of the benefits of silicon (Si) supplementation in turfgrass have had inconsistent results. This study assessed the effect of Si supplementation on biomass production and Si accumulation of tall fescue (Festuca arundinacea) and bentgrass (Agrostis stolonifera). Plants were grown in buffered Hoagland’s media (pH 6) with four sodium silicate (Na₂SiO₄) treatments (0, 0.5, 1, 2, and 4 mM Si). The two species responded differently to Si supplementation in terms of biomass. For bentgrass, biomass was enhanced by Si supplementation, but only significantly (p < 0.05) at the highest concentration (4 mM Si). Lower Si concentrations (0.5, 1, and 2 mM Si) significantly increased biomass in tall fescue compared to control, but there was no increase in biomass at 4 mM Si. There was a positive linear relationship between Si concentrations in media and Si concentrations in tissue. At 4 mM Si, the Si concentrations in aboveground tissue of tall fescue and bentgrass averaged 24 and 30.5 g kg⁻¹dry mass, respectively. Elevated Si concentrations in growth media promoted formation of silica bodies. The highest Si rates (4 mM Si) resulted in the highest silica body areal coverage in leaves of both species. We observed two silica body morphologies (which we termed long and barbed). Our findings indicate that tall fescue is likely to benefit from Si supplementation when soil pore water dissolved Si is below 0.5 mM, but increases in soil pore water dissolved Si above 2 mM are unlikely to increase biomass. In contrast, benefits in bentgrass may only be realized if dissolved Si in pore water is increased to 4 mM.