Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Growstones ideal alternative to perlite, parboiled rice hulls

Substrate made from waste glass performs well in greenhouse applications

In the greenhouse business, organic and inorganic growing substrates are chosen for the physical and chemical properties necessary to support specific crops and growing conditions. One important physical property in substrates is air-filled pore space, a particularly important characteristic that allows for gas exchange between plants' roots and the outside atmosphere.

Perlite and parboiled rice hulls are the two of the most common components used to increase air-filled pore space (AFP) in substrates. A study compared these popular components to Growstones, an aggregate produced from finely ground waste glass.

Although they are widely used in horticulture applications, both perlite and parboiled rice hulls have disadvantages and limitations. Perlite, a natural glass of volcanic origin that expands when quickly heated, has become increasingly expensive due to costs of mining, transportation, and production. In addition to its rising price tag, perlite produces a siliceous dust that is an eye and lung irritant. Parboiled rice hulls (PBH) are produced only in specific areas of the United States, making high shipping costs an issue for end-users. And, because it is a plant-based component, PBH may also have limitations with respect to its use in long-term crops because of softening and decomposition.

Michael R. Evans, Professor in the Department of Horticulture at the University of Arkansas, created experiments to compare perlite and PBH with Growstones. Evans' results were published in HortTechnology. According to Evans, aggregates such as Growstones (produced by Earthstone Corp., Santa Fe, NM) have been proposed as alternatives to perlite and PBH to adjust the physical properties of peat-based substrates.

Growstones, which have been successfully used as a hydroponic substrate, are produced from finely ground waste glass. The ground glass powder is combined with calcium carbonate and heated in a kiln. Carbon dioxide is produced as the glass particles are heated and fused together, trapping air spaces inside the glass. The result is an expanded, lightweight product that is cooled before being ground to the desired size.

Evans' experiments showed that Growstones had an AFP higher than that of both peat and perlite. Additionally, when added to peat at a concentration of at least 15%, Growstones increased the AFP of the resulting peat-based substrate.

"Growstones can be used in a similar manner to perlite and PBH as an aggregate to increase AFP of peat based substrates", Evans said. "The primary differences were that, at concentrations of 25% or more, GS resulted in a higher AFP than equivalent perlite-containing substrates. Also, substrates containing 20% or more GS had a higher water-holding capacity than equivalent perlite- and PBH-containing substrates, and GS-containing substrates had a higher bulk density than equivalent perlite- and PBH-containing substrates."

All GS-containing substrates had physical properties within recommended ranges. Vinca, impatiens, and geranium plugs grown in GS-containing substrates were comparable to plants grown in equivalent perlite- and PBH-containing substrates.

Evans said that the experiments showed that Growstones can be successfully used as a component for substrates used in greenhouse crop production.

The complete study and abstract are available on the ASHS HortTechnology electronic journal web site:

Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education, and application.

Michael W. Neff | EurekAlert!
Further information:

More articles from Agricultural and Forestry Science:

nachricht Algorithm could streamline harvesting of hand-picked crops
13.03.2018 | University of Illinois College of Engineering

nachricht A global conflict: agricultural production vs. biodiversity
06.03.2018 | Georg-August-Universität Göttingen

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

Im Focus: ILA 2018: Laser alternative to hexavalent chromium coating

At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.

When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...

Im Focus: Radar for navigation support from autonomous flying drones

At the ILA Berlin, hall 4, booth 202, Fraunhofer FHR will present two radar sensors for navigation support of drones. The sensors are valuable components in the implementation of autonomous flying drones: they function as obstacle detectors to prevent collisions. Radar sensors also operate reliably in restricted visibility, e.g. in foggy or dusty conditions. Due to their ability to measure distances with high precision, the radar sensors can also be used as altimeters when other sources of information such as barometers or GPS are not available or cannot operate optimally.

Drones play an increasingly important role in the area of logistics and services. Well-known logistic companies place great hope in these compact, aerial...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

International Virtual Reality Conference “IEEE VR 2018” comes to Reutlingen, Germany

08.03.2018 | Event News

Latest News

Wandering greenhouse gas

16.03.2018 | Earth Sciences

'Frequency combs' ID chemicals within the mid-infrared spectral region

16.03.2018 | Physics and Astronomy

Biologists unravel another mystery of what makes DNA go 'loopy'

16.03.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>