Submitted to: The Buckeye
Publication Type: Trade Journal
Publication Acceptance Date: 9/17/2014
Publication Date: 9/28/2014
Citation: Altland, J.E. 2014. A new lime material for container substrates. The Buckeye. 25(8):28-31.
Technical Abstract: The primary component in greenhouse potting substrates is sphagnum peatmoss. Substrate solution pH of non-amended peatmoss ranges from 4.0 to 4.5. Ideal pH for most greenhouse floriculture crops ranges from 5.8 to 6.2. Dolomitic lime is most often used to elevate substrate pH in peatmoss-based media. Steel slag is a byproduct of the steel industry, recently introduced as a liming agent for agricultural purposes and has potential for use in greenhouse substrates. This article describes research to quantify and model the impact of steel slag on pH of a peatmoss-based greenhouse substrates, and compare it to the industry standard dolomitic lime. The ability to raise substrate pH was much greater for steel slag than dolomitic lime. This might have some application for greenhouse or nursery producers where very high pH is desired or there is some need to counteract a very acidic or pH-lowering amendment. Most crops are grown at pH between 5.8 and 6.2, levels that are attainable with dolomitic lime. Furthermore, over-application of steel slag could result in exceedingly high pH whereas even a gross over-application of dolomitic lime would, based on the results of these experiments, result in pH no higher than 6.6. While steel slag offers more immediate and effective liming power when high pH (>7) is desired, dolomitic lime offers an ideal Ca : Mg ratio, more moderate pH increases, and less risk of high pH with accidental over-application.