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Polystyrene Foam Aggregates in Greenhouse Substrates

Wed, Apr 24th, 2019, created by W. Garrett Owen
Greenhouse soilless substrates are formulated from various components and amendments. Traditional greenhouse soilless substrate components include peat moss, aged bark, perlite, and/or vermiculite.

However, an increased emphasis on sustainability has heightened interests in alternative greenhouse substrates and components. In today’s greenhouse industry, one may find coconut coir or wood fiber used as an alternative to peat moss. Not only has peat moss alternatives been of interest,but researchers and growers have trialed and implemented alternative ‘organic’and ‘non-organic’ greenhouse aggregates to replace perlite.

These alternatives include parboiled rice hulls, processed corncob, pine wood chips, pecan shells, city green wastes, bovine bones, shredded rubber, plastic beads, polystyrene foam beads, glass beads and so on. With this increased emphasis on sustainability in greenhouse production, it is rare to see the implementation of ‘non-organic’substrate components. However, during recent greenhouse visits, polystyrene foam beads or aggregates were observed in greenhouse substrates. Used as an alternative to perlite, the polystyrene foam aggregates were white, round to blockular in shape and were either observed as a singular aggregate or clump of aggregates.

Though polystyrene foam aggregates do not influence substrate pH or electrical conductivity (EC),they can migrate upward through the substrate during irrigation events and settle on the substrate surface. Once on top, the aggregate can become windblown or splashed from containers to litter the greenhouse floor and have other impacts on the cleanliness of the greenhouse and surrounding environment.

Therefore, if one chooses to utilize polystyrene foam aggregates as an alternative to perlite, keep in mind the potential for the issues described above to occur. If possible, greenhouse growers should consider utilizing greenhouse substrates formulated with ‘organic’ or derived from renewable resources to avoid these problems.



About the Author:

W. Garrett Owen

Greenhouse Outreach Specialist, Michigan State University

W. Garrett Owen is the Eastern Michigan Floriculture and Controlled-environment horticulture Outreach Specialist with Michigan State University based in Novi, MI. He has an appointment split between Outreach and research. His areas of research interest include propagation and production, nutrition, growth regulation, cold hardiness, and production problem diagnostics.

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