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Raymond A. Cloyd and Amy Dickinson

Fungus gnats (Bradysia spp.) are major insect pests in greenhouses. The adult stage is primarily a nuisance whereas the larval stage is directly responsible for plant injury by feeding on plant roots or tunneling into stems. Insecticides are used to deal with fungus gnat larvae in growing medium, although sometimes with limited success. This study evaluated the potential of using a soil amendment—diatomaceous earth (DE) incorporated into growing media—for controlling the fungus gnat Bradysia sp. nr. coprophila. Two experiments were conducted by testing a series of growing media containing various concentrations of diatomaceous earth, and several without diatomaceous earth. The effects of the growing media containing diatomaceous earth on both the 2nd and 3rd instars of fungus gnat larvae were determined by recording the number of adults captured on yellow sticky cards (2.5 × 2.5 cm). Based on the results obtained from both experiments, the addition of DE to growing medium, at the concentrations tested, did not negatively affect or increase efficacy against both the 2nd and 3rd instars. This suggests that incorporating DE into commercially available growing medium may not be beneficial to greenhouse producers. However, further research is needed to assess whether differential larval susceptibility and moisture content influence the ability of DE to control soil-dwelling arthropods.

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John J. Sloan, Raul I. Cabrera, Peter A.Y. Ampim, Steve A. George and Wayne A. Mackay

diffuse out of those pores when the expanded shale aggregate is again surrounded by water ( Sloan et al., 2000 ). This property could make expanded shale a beneficial ingredient of growing media, especially when combined with decomposable organic materials

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Yinping Li, Raymond A. Cloyd and Nora M. Bello

media, 2) the effect of pyriproxyfen in two growing media on western flower thrips pupae, and 3) the residual activity of pyriproxyfen in growing medium on western flower thrips pupae 3, 5, 7, and 14 d after treatments were applied. Materials and Methods

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Hanna Y. Hanna

increase plant yield to gain a fair market share among major producers. Previous research has indicated that perlite growing media can be recycled to save money ( Hanna, 2005 , 2006 ), and precision heating can reduce production costs ( Hanna and Henderson

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Nadia Jiménez-Peña, Luis A. Valdez-Aguilar, Ana M. Castillo-González, María T. Colinas-León, Andrew D. Cartmill and Donita L. Cartmill

nutrients in the media solution and the physical and chemical properties of the growing media may affect the response of plants to a specific substrate and nutrient solution formulation. Tree bark is a traditionally used media for orchid cultivation in

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Samuel E. Wortman, Michael S. Douglass and Jeffrey D. Kindhart

, both of these challenges can be at least partially addressed by growing strawberries in a hydroponic system within high tunnels. Hydroponic production, through the use of nutrient solution or soilless substrates as growing media, eliminates weed

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G.O. Hood

Horticultural schools are always looking for fresh material for their classes. The Canadian Sphagnum Peat Moss Association (CSPMA) has developed a lesson plan entitled Growing Media and Soil Amendment that is ideal for horticultural or greenhouse management courses. The teaching plan includes terms and definitions on all types of peatmoss and commonly used terms related to the resource. It discusses characteristics and qualities of world peat resources as well as comparisons of physical, chemical, and biological properties of organic materials used in growth media and as soil amendments. In addition to the research information on peat and other soil amendments, the teaching plan addresses the environmental issues surrounding the use of wetlands, including peatlands and the effects of peat harvesting on the environment. The plan introduces students and instructors to the reclamation and restoration efforts that have been developed and used to preserve the harvested bogs in Canada. The curriculum is divided into two sections: one for the students, which includes handouts and one for the instructor, with more in-depth background information.

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Michael Compton and Timothy Zauche

Soilless horticultural growing media are composed of organic matter, coarse aggregates, nutrients, and a wetting agent. Sphagnum peat has been the standard organic addendum to soilles growing media. However, recent shortages, escalating costs, and its acidity make sphagnum peat a sometimes less-than-desirable material. Alternatives such as composted bark dust, coconut coir, composted manure, and crop by-products have been proposed as substitutes for sphagnum peat, but none are a suitable general alternative. Anaerobic digestion-derived biosolids (ADB) has the potential to become a complete or partial substitute for sphagnum peat. ADB is a cellulosic product similar in appearance to sphagnum peat and is a product from the anaerobic digestion of cattle manure for 14 to 25 days at temperatures between 104 °F. and 140 °F. Bacteria from the animal's rumen, present in the manure prior to anaerobic digestion, are used to breakdown excessive nutrients present in the manure. Following anaerobic digestion, the nutrient-rich liquid phase is removed to yield an odorless cellulosic fiber that is sterile, free of weeds, pests, and pathogens, as well as uniform and reproducible. The potential application of ADB to the horticulture industry, most specifically as an organic addendum to soilless media, is immense and will be discussed. Use of anaerobic digester-derived biosolids in horticultural growing media is a protected intellectual property and available for license through the WiSys Technology Foundation.

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Stephanie Rademan and Dyremple Marsh

A wide range of methodologies, ranging from Leonard jar to growth pouch have been used to investigate the nitrogen fixation process in leguminous crops. The effectiveness of most of these research methods have been questioned. Problems encountered vary from difficulty in root separation to water log conditions. This study was undertaken to determine the effect of different growing media on nodule development and harvestability. Black and Red seed coat kidney bean were surface sterilized and inoculated with the Rhizobium phaseoli strain UMR 1899. Seeds were planted in 8.5 cm diameter sterile clay pots containing the respective growing medium. These growing media were sand, Promix GM, Promix BX, and fritted clay. The black seed coat kidney bean had higher germination rate under all media for all dates recorded. Black kidney bean grown in sand and fritted clay had plant heights significantly greater than ones grown in the other media on the third harvest date. Nodule activities as measured by shoot dry weight and nodule number were significantly higher in both beans grown in fritted clay than in other media. Promix GM plants with dry weight of .45g for the black bean and .32g for the red beans were the lowest. Nodule separation from the growing media was easiest when plants were grown in sand, however, this was not significantly different from that of plants grown in fritted clay.

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Tomasz Anisko, D. Scott NeSmith and Orville M. Lindstrom

The time-domain reflectometry (TDR) method of measuring water content has been applied to mineral soils but not to organic growing media. We investigated the applicability of TDR for measuring the water content of organic media in containers. TDR calibration was conducted for sand, peat, composted pine bark, sand and peat mix, sand and bark mix, and a commercial growing medium (Metro Mix 300). Regression analysis of volumetric water content was conducted with the ratio of apparent: physical length of the probe (La: L) as an independent variable. The calibration curve for Metro Mix 300 was compared to curves generated for a range of soils by other investigators. Additionally, water-content and La: L changes were monitored in Metro Mix 300 for 10 months and were compared to predicted values from the calibration curve. Organic media had a higher water content than sand for the same La: L value. Equations developed by previous authors generally underestimated water content when compared with the calibration curve for Metro Mix 300. We attribute this difference to a large fraction of highly decomposed organic matter or vermiculite and, thus, to the presence of more bound water. Specific calibration of TDR may be required to determine the absolute water content of organic growing media.