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Dewayne L. Ingram, Charles R. Hall, and Joshua Knight

Life cycle assessment (LCA) was used to analyze the global warming potential (GWP) and variable costs of production system components for an 11.4-cm container of wax begonia (Begonia ×semperflorens-cultorum Hort) modeled in a gutter-connected, Dutch-style greenhouse with natural ventilation in the northeastern United States. A life cycle inventory of the model system was developed based on grower interviews and published best management practices. In this model, the GWP of input products, equipment use, and environmental controls for an individual plant would be 0.140 kilograms of carbon dioxide equivalents (kg CO2e) and the variable costs would total $0.666. Fifty-seven percent of the GWP and 43% of the variable costs would be due to the container and the portion of a 12-plant shuttle tray assigned to a plant. Electricity for irrigation and general overhead would be only 13% of GWP and 2% of variable costs. Natural gas use for heating would be 0.01% of GWP and less of the variable costs, even at a northeastern U.S. location. This was because of the rapid crop turnover and only heated for 3 months of a 50-week production year. Life cycle GWP contributions through carbon sequestration of flowering annuals after being transplanted in the landscape would be minor compared with woody plants; however, others have documented numerous benefits that enhance the human environment.

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Dewayne L. Ingram, John M. Ruter, and Chris A. Martin

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Dewayne L. Ingram, Charles R. Hall, and Joshua Knight

Understanding carbon footprint (CF) terminology and the science underlying its determination is important to minimizing the negative impacts of new product development and assessing positive or negative cradle-to-grave life-cycle impacts. Life cycle assessment has been used to characterize representative field-grown and container-grown landscape plants. The dominant contributor to the CF and variable costs of field-grown trees is equipment use, or more specifically, the combustion of fossil fuels. Most of that impact is at harvest when heavy equipment is used to dig and move individual trees. Transport of these trees to customers and the subsequent transplant in the landscape are also carbon-intensive activities. Field-grown shrubs are typically dug by hand and have much smaller CFs than trees. Plastics are the major contributor to CF of container-grown plants. Greenhouse heating also can be impactful on the CF of plants depending on the location of the greenhouse or nursery and the length and season(s) of production. Knowing the input products and activities that contribute most toward CF and costs during plant production allows nursery and greenhouse managers to consider protocol modifications that are most impactful on profit potential and environmental impact. Marketers of landscape plants need information about the economic and environmental life-cycle benefits of these products, as they market to environmentally conscious consumers.

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Dewayne L. Ingram, Charles R. Hall, and Joshua Knight

A model production system for a 15.2-cm poinsettia (Euphorbia pulcherrima) in the north Atlantic region of the United States was developed through grower interviews and best management practices and analyzed using a life cycle assessment (LCA). The model system involved direct sticking of unrooted cuttings. The propagation phase was 4 weeks, followed by 9 weeks of irrigation using a boom system and 4 weeks of flood-floor irrigation. The carbon footprint, or global warming potential (GWP), for the plant was calculated as 0.474 kg carbon dioxide equivalent (kg CO2e), with a variable cost of $1.030. Major contributors to the GWP were the substrate and filling pots, fertilization, the container, irrigation, and overhead electricity. The major contributors to variable costs were the unrooted cuttings and labor to prepare and stick ($0.471). Furthermore, the substrate and filling containers and irrigation were notable contributors. Material inputs accounted for 0.304 kg CO2e, whereas equipment use was estimated to be 0.163 kg CO2e, which comprised 64.2% and 35.8% of total GWP, respectively. Material inputs accounted for $0.665 (64.6%) of variable costs, whereas labor accounted for 19.6% of variable costs for this model. Water use per plant was 77.2 L with boom irrigation for the 9 weeks during production spacing (32.8 plant/m2) and represented 64% of the total water use. LCA was an effective tool for analyzing the components of a model system of greenhouse-grown, flowering, potted plants. Information gained from this study can be used by growers considering system alterations to improve efficiency.

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Thomas H. Yeager, Rebecca H. Harrison, and Dewayne L. Ingram

Ilex crenata Thunb. `Rotundifolia' grown in sand culture with the root zone at 40C for 6 hours daily had smaller root and shoot dry weights after 6 weeks than plants grown with root zones at 28 or 34C. Root and shoot N accumulation (milligrams N per gram of dry weight) decreased when root-zone temperatures were increased from 28 to 40C and plants were fertilized twice dally with either 75, 150, or 225 mg N/liter. Nitrogen application rates of 150 or 225 mg·liter-1 resulted in increased root and shoot N accumulation for plants grown with root zones at either 28, 34, or 40C compared with the 75 mg N/liter treatment. Increased N fertilization rates did not alleviate reduced plant growth due to the high root-zone temperature.

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Dewayne L. Ingram, Charles R. Hall, and Joshua Knight

Three scenarios for production of Buxus microphylla var. japonica [(Mull. Arg.) Rehder & E.H. Wilson] ‘Green Beauty’ marketed in a no. 3 container on the west coast of the United States were modeled based on grower interviews and best management practices. Life cycle inventories (LCIs) of input products, equipment use, and labor were developed from the protocols for those scenarios and a life cycle assessment (LCA) was conducted to determine impact of individual components on the greenhouse gas emissions (GHGs) and the subsequent carbon footprint (CF) of the product at the nursery gate and in the landscape. CF is expressed in global warming potential (GWP) for a 100-year period in units of kilograms of carbon dioxide equivalents (kg CO2e). The GWP of the plant from Scenario A (propagation to no. 1 to 3 container) was 2.198 kg CO2e with variable costs of $4.043. Scenario B (propagation to field to no. 3 container) would result in a GWP of 1.717 kg CO2e with variable costs of $2.880 and take a year longer in production than the other two models. The GWP of Scenario C (propagation to no. 1 to no. 2 to no. 3 containers) would be 3.364 kg CO2e with variable costs of $5.733. Containers, transplants/transplanting, irrigation, and fertilization input products and associated activities accounted for the greatest portion of GHG and variable costs in each scenario. Pruning, assembling/load trucks, pesticides, and chlorination were other important components to variable costs of each scenario but had little impact on GWP. Otherwise, the major contributors to GWP are also major contributors to cost.

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William J. Foster, Dewayne L. Ingram, and Terril A. Nell

Rooted stem cuttings of Ilex crenata Thunb. `Rotundifolia' were grown in a controlled-environment growth chamber. Root-zone temperatures were controlled with an electric system. Shoot carbon exchange and root respiration rates were determined in response to root-zone temperatures of 28, 32, 36, and 40C for 6 hour·day–1 for 7 days. Photosynthesis was decreased by root zones ≥ 32C, while root respiration increased with increasing root-zone temperature. Decreased photosynthetic rates were not due to increased stomatal resistance.

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Victoria M. Anderson, Douglas D. Archbold, Robert L. Geneve, Dewayne L. Ingram, and Krista L. Jacobsen

Organic and low-input production systems are increasingly of interest in medicinal plant production, such as Calendula officinalis, a medicinal plant grown for essential oils. However, in these systems the effects of nutrient availability and water stress may act singularly or in combination to affect plant growth and medicinal compound production. This study investigated the effects of organic and conventional fertility sources and drought stress effects on four calendula cultivars. Soil nitrogen (N) status, plant growth, productivity, and essential oil quality and quantity were measured. The plant growth response to increased N availability varied by cultivar, indicating that some cultivars may be better suited to low-input fertility regimes. Fertility source did not significantly affect essential oil quality or quantity. Drought stress reduced plant growth but increased the quality of essential oil, as indicated by the concentrations of specific constituents, although it did not reduce total oil yield. These results indicate that organic and low-input farming systems may significantly reduce plant growth, but may not necessarily affect essential oil yield or quality. As such, the sustainability of medicinal plant production systems may be improved by reductions in water and conventional fertilizers without significant reductions in medicinal compound production.

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Dewayne L. Ingram, Timothy A. Woods, Wuyang Hu, and Susmitha S. Nambuthiri

Increasing demand for groundcover plants and increasing consumer preference for more sustainable products encourage nursery crop producers and landscape management companies to assess efficiency and sustainable practices. Ajuga reptans ‘Bronze Beauty’ and Sedum kamtschaticum ‘Variegatum’ were grown in standard plastic containers or plantable containers (Ellepot and SoilWrap) and 12- or 18-count flats. These production alternatives were presented in personal surveys of commercial industry personnel and consumers to determine their willingness to pay for these attributes. A conjoint analysis revealed an affinity for both groups to purchase flats of groundcovers and preferred sedum over ajuga. Commercial buyers from larger companies were more likely to purchase plantable containers than those from smaller firms. Generally, flats of Ellepots were preferred over flats of SoilWraps and 18-count over 12-count flats by commercial buyers. Price had a negative impact on consumer willingness to pay. Consumers revealed no specific preference for the plantable containers, although preference for plastic containers declined with age and presence of children at home.

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Christopher Ramcharan, Dewayne L. Ingram, Terril A. Nell, and James E. Barrett

Short-term effects of root-zone temperatures (RZT) of 28, 33, 38, and 43C for 6 hours daily on container-grown Musa spp. (AAA) `Grande Naine' and Ixora chinensis L. `Maui' were determined under greenhouse and growth room conditions. Diurnal fluctuation of leaf carbon assimilation (LCA) was altered by treatments. In the growth room at 43C, the maximum LCA occurred about midday for banana, but not until afternoon in ixora. LCA was highest (0.53 mg CO2/m2 per sec) in banana with a 33C RZT under greenhouse conditions, while it was equally high (0.74 mg CO2/m2 per sec) at 33 and 38C in a growth room. In ixora, 33C induced the highest LCA (0.40 mg CO2/m2 per sec) in the greenhouse at 1200 hr, but there were no apparent differences in midday LCA between plants with RZT of 28, 33, and 38C in the growth room. Effects of RZT and environment on the daily fluctuations of gaseous exchange processes raise questions about using measurements at only one time during the day to separate treatment effects.