College of Agriculture & Natural Resources
Permanent URI for this communityhttp://hdl.handle.net/1903/1598
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item MODIFYING GREEN ROOF SUBSTRATE FOR NUTRIENT RETENTION IN URBAN FARMING SYSTEMS(2020) Howard, Ian Nathaniel; Lea-Cox, John D; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Interest in urban agriculture is steadily increasing in the Mid-Atlantic region. The conversion of extensive green roofs to food production is particularly appealing due to space availability. The modification of a relatively unfertile shale-based substrate for increased water and nutrient availability was investigated, adding mushroom and yard-waste composts, but potentially contributing to nutrient runoff from rainfall and irrigation events. Alumina and biochar were therefore tested as substrate amendments to determine their effect nutrient availability and retention. Fifteen substrate mixes were screened by column leaching tests, and four were further studied over nine-months, with crop and leachate studies. Basil, lettuce and peppers were grown and harvested in succession in replicated 50-liter tubs, with leachate collection systems. Biochar did not reduce nitrogen or phosphorus leaching and did not have an effect on plant growth. Alumina significantly reduced the amount of phosphorus leached from substrates with little to no effect on plant growth.Item A Comparison of Organic Matter Amendments for Use in Extensive Green Roof Substrates(2015) Barton, Elizabeth Taussig; Lea-Cox, John D; Cohan, Steven M; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Organic matter is important for water retention and nutrient availability in green-roof systems. Yet few quantitative green-roof studies provide data for various sources of organic matter (OM). Coconut coir (CC), rice hulls (RH), SmartLeaf® (SL), and mushroom compost (MC) were used as green roof substrate amendments. The effects of OM on water-holding capacity, nutrient availability and plant establishment were measured. Growth of Phedimus kamtschaticus was greater with MC or SL compared to CC or RH. Substrate moisture and nutrient availability were significantly affected by OM source during an 8-month rooftop experiment and a 6-month growth chamber study. Coconut coir showed high moisture retention, low nutrient availability and low aboveground biomass, indicating that nutrient availability is crucial to successful plant growth and establishment on a green roof. Composted materials such as MC and SL that have higher levels of available nutrients, promote better growth than unprocessed materials like RH and CC.Item The comparative effects of three Sedum species on green roof stormwater retention(2013) Starry, Olyssa; Lea-Cox, John; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Green roofs are typically dominated by Sedum species because they can tolerate hot, xeric environments. However, due to their high water use efficiency, some have questioned the selection of these species for stormwater management. We investigated (1) how three common Sedum species contribute to overall stormwater retention efficiency by green roofs in the mid-Atlantic region, and (2) whether species-specific differences in water use could be explained by morphological and physiological characteristics. Water use and CO2 exchange were continuously monitored in growth chamber studies under increasing drought stress for S. album, and S. kamtschaticum, two species known to variably cycle between CAM and C3 metabolisms. Under fall temperature conditions, S. kamtschaticum had gas exchange rates akin to C3 photosynthesis and used 35% more water compared to S. album. Interestingly, S. album conserved water and had malic acid accumulation confirming CAM metabolism for the duration of the experiment, even under well-watered conditions. In field studies, sixteen replicate green roof platforms (n=4 per species) were planted with S. album, S. kamtschaticum, S. sexangulare, or left unplanted during summer 2010. The platforms were monitored intensively for canopy growth, leaf area, root biomass, substrate moisture and runoff for two years (2011 and 2012). Plant treatment effects on stormwater runoff were significant, but most discernible for small and intermediate-sized rainfall events less than 62.5mm. The two species with the greatest stormwater retention efficiencies, S. kamtschaticumand S. sexangulare, also had the highest rates of evapotranspiration (ET), and higher ET rates resulted in less total runoff. Because evapotranspiration was identified as important for predicting performance by plants in the field study, I investigated how ET data from this study, combined with environmental data collected from a weather station at the study site, could be used to improve the application of the FAO56 Penman-Monteith evapotranspiration equations to green roofs. The incorporation of specific seasonal crop coefficients were found to improve correlations between predicted and measured rates of ET and these coefficients were related to plant characteristics. The refinement of ET equations can lead to more accurate hydrologic models of green roofs and design and management tools.Item Ecologically Inspired Design of Green Roof Retrofit(2007-08-13) Schumann, Laura Marie; Tilley, David R; Biological Resources Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Green roofs are becoming popular in the United States for their runoff and energy reduction abilities. However, current designs have high installation costs, heavy load-bearing requirements, and restrictions to low-sloped roofs. We designed a novel retrofit technology, the green cloak, which uses fast-growing vine species and a trellis to suspend vegetation above a roof. We conducted field experiments, prototype testing, and mathematical modeling to determine the effect of the green cloak on stormwater runoff and indoor summertime building temperature reduction. We assessed energy and monetary cost-benefits. The green cloak reduced July indoor building temperature by 11.3°C which saved 73% of cooling energy costs. The green cloak delayed the peak storm runoff from a 0.15mm/min storm by 100 minutes. The green cloak costs 38% less than a green roof. The green cloak demonstrated great potential for mitigating runoff impacts of impervious surfaces, reducing summer temperatures of buildings, and creating urban greenery.