Dissolution of silicon from soilless substrates and additives

Authors: DEY, MACKENZIE - Utah State University; Boldt, Jennifer; BUGBEE, BRUCE - Utah State University

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/2023
Publication Date: 9/23/2023
Citation: Dey, M.G., Boldt, J.K., Bugbee, B. 2023. Dissolution of silicon from soilless substrates and additives. HortScience. 58(11):1282-1290. https://doi.org/10.21273/HORTSCI17189-23.
DOI: https://doi.org/10.21273/HORTSCI17189-23

Interpretive Summary: Silicon helps minimize plant stress caused by adverse growing conditions, pests, or diseases. It can improve plant quality and reduce yield losses. Growers can supply supplemental silicon to plants by applying a liquid fertilizer or by mixing an amendment into the growing media. The choice may depend on cost, ease of application, and frequency of application. An ideal amendment for container-grown crops should steadily release silicon throughout the cropping cycle. We identified two silicon-containing amendments, wollastonite and rice hulls, that released silicon at sufficient quantities for use in growing potted plants. Wollastonite would be well-suited for crops grown less than four months, and rice hulls would provide extended release of silicon for longer-duration crops. This information will help growers select a supplemental silicon source amenable for their crop and production facility.

Technical Abstract: Silicon (Si) is a beneficial element that is usually ample in soil solution but is minimally bioavailable from soilless substrates. Several Si additives are commercially available, but the rate of dissolution of Si from these additives is not well characterized. The ideal additive would steadily release bioavailable Si over time. Here we report the long-term (120 day) dissolution of Si from soilless substrates and substrate additives in water and in peat-based media. In gently agitated containers with deionized-water, perlite, sphagnum peat, vermiculite, and coconut coir released less than 0.03 mmol Si per L substrate per day; rice hulls steadily released 0.2 mmol Si per L rice hulls per day; and wollastonite (VanSil® W-10), a calcium-silicate mineral, steadily released 4 mmol Si per L wollastonite per day. The release rate of rice hulls and wollastonite was further studied in peat-based media. Leachate from media amended with 1 g wollastonite per L peat peaked at 2.1 mmol Si per L media per leaching event (day 10) then gradually decreased over 120 days. The peak release of Si from media amended with 12% rice hulls was similar, but instead gradually increased over time. After 120 days, both amendments increased the pH of peat by about 1 pH unit, but this same increase occurred in 7 days in a coconut coir substrate. These results suggest that both amendments steadily release Si for up to four months and would be beneficial for long-term, container grown crops.