Silicon accumulation by sunflowers at low substrate pH

Authors: Boldt, Jennifer; Banks, Mona-Lisa; Altland, James

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2022
Publication Date: 10/25/2023
Citation: Boldt, J.K., Banks, M.L., Altland, J.E. 2023. Silicon accumulation by sunflowers at low substrate pH. Acta Horticulturae. 1377:739-746. https://doi.org/10.17660/ActaHortic.2023.1377.90.
DOI: https://doi.org/10.17660/ActaHortic.2023.1377.90

Interpretive Summary: Silicon can help alleviate plant stress caused by environmental conditions, pests, or diseases. This can improve plant quality, reduce yield losses, and/or reduce the amount of pest protection products applied to crops. In developing silicon application strategies for greenhouse crops, it is important to consider whether substrate pH will impact silicon uptake. Across the substrate pH range recommended for containerized production using soilless substrates, leaf silicon concentrations of sunflowers were similar. This information will enable greenhouse growers to select a uniform application rate for silicon independent of substrate pH at the time of application.

Technical Abstract: Supplemental silicon (Si) is becoming more-widely applied in container soilless substrates to mitigate crop stress. The objective of this study was to evaluate the effect of soilless substrate pH on foliar Si accumulation. Sunflowers (Helianthus annuus L. ‘Pacino Gold’) were grown in 11.5-cm diameter pots filled with an 85 peat : 15 perlite (v:v) substrate amended with 0 to 4.75 kg·m-3 dolomitic lime, in treatment increments of 0.59 kg·m-3, and supplemented weekly with 150 mL of either 0 or 2 mM potassium silicate. Plants were grown in a greenhouse with ambient irradiance and photoperiod. Pour-through leachate pH increased with increased lime incorporation. Five weeks after transplant, pH ranged from 3.27 to 5.66 (pooled across Si treatments). Leaf Si concentration was lowest in the 0 and 0.59 kg·m-3 lime treatments and increased quadratically with lime rate. Maximum dry mass occurred at 3.18 kg·m-3 lime (final substrate pH of 5.27) and maximum leaf Si concentration occurred at 3.62 kg·m-3 lime (final substrate pH of 5.39). Overall, substrate pH values between 4.53 and 5.66, corresponding to lime rates of 1.19 to 4.75 kg·m-3, did not impact growth or supplemental Si accumulation in sunflower.