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Chris A. Martini, Dewayne L. Ingram, and Terril A. Nell

Growth of Magnolia grandiflora Hort. `St. Mary' (southern magnolia) trees in containers spaced 120 cm on center was studied for 2 years. During the 1st year, trees were grown in container volumes of 10, 27, or 57 liter. At the start of the second growing season, trees were transplanted according to six container shifting treatments [10-liter containers (LC) both years, 10 to 27LC, 10 to 57LC, 27LC both years, 27 to 57LC, or 57LC both years]. The mean maximum temperature at the center location was 4.8 and 6.3C lower for the 57LC than for the 27 and 10LC, respectively. Height and caliper, measured at the end of 2 years, were” greatest for magnolias grown continuously in 27 or 57LC. Caliper was greater for trees shifted from 10LC to the larger containers compared with trees grown in 10LC both years. Trees grown in 10LC both years tended to have fewer roots growing in tbe outer 4 cm of the growing medium at the eastern, southern, and western exposures. During June and August of the 2nd year, high air and growth medium temperatures may have been limiting factors to carbon assimilation. Maintenance of adequate carbon assimilation fluxes and tree growth, when container walls are exposed to solar radiation, may require increasing the container volume. This procedure may be more important when daily maximum air temperatures are lower during late spring or early fall than in midsummer, because low solar angles insolate part of the container surface.

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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, 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.

Open access

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

The production components of an evergreen shrub (Ilex crenata ‘Bennett’s Compacta’) grown in a no. 3 container in an east coast U.S. nursery were analyzed for their costs and contributions to carbon footprint, as well as the product impact in the landscape throughout its life cycle. A life cycle inventory was conducted of input materials, equipment use, and all cultural practices and other processes used in a model production system for this evergreen shrub. A life cycle assessment (LCA) of the model numerated the associated greenhouse gas emissions (GHG), carbon footprint, and variable cost of each component. The LCA also included the transportation and transplanting of the final product in the landscape as well as its removal after a 40-year useful life. GHG from input products and processes during the production (cutting-to-gate) of the evergreen shrub were estimated to be 2.918 kg CO2e. When considering carbon sequestration during production weighted over a 100-year assessment period, the carbon footprint for this model system at the nursery gate was 2.144 kg CO2e. Operations, combining the impact of material and equipment use, that contributed most of GHG during production included fertilization (0.707 kg CO2e), the liner and transplanting (0.461 kg CO2e), the container (0.468 kg CO2e), gravel and ground cloth installation (0.222 kg CO2e), substrate materials and preparation (0.227 kg CO2e), and weed control (0.122 kg CO2e). The major contributors to global warming potential (GWP) were also major contributors to the cutting-to-gate variable costs ($3.224) except for processes that required significant labor investments. Transporting the shrub to the landscaper, transporting it to the landscape site, and transplanting it would result in GHG of 0.376, 0.458, and 0 kg CO2e, respectively. Variable costs for postharvest activities were $6.409 and were dominated by labor costs (90%).

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

The components for two production systems for young foliage plants in 72-count propagation trays were analyzed using life cycle assessment (LCA) procedures. The systems differed by greenhouse type, bench size and arrangement, rainwater capture, and irrigation/fertilization methods. System A was modeled as a gutter-connected, rounded-arch greenhouse without a ridge vent and covered with double-layer polyethylene, and the plants were fertigated through sprinklers on stationary benches. System B was modeled as a more modern gutter-connected, Dutch-style greenhouse using natural ventilation, and moveable, ebb-flood production tables. Inventories of input products, equipment use, and labor were generated from the protocols for those scenarios and a LCA was conducted to determine impacts on the respective greenhouse gas emissions (GHG) and the subsequent carbon footprint (CF) of foliage plants at the farm gate. CF is expressed in global warming potential for a 100-year period (GWP) in units of kilograms of carbon dioxide equivalents (kg CO2e). The GWP of the 72-count trays were calculated as 4.225 and 2.276 kg CO2e with variable costs of $25.251 and $24.857 for trays of foliage plants grown using Systems A and B, respectively. The GWP of most inputs and processes were similar between the two systems. Generally, the more modern greenhouse in System B was more efficient in terms of space use for production, heating and cooling, fertilization, and water use. While overhead costs were not measured, these differences in efficiency would also help to offset any increases in overhead costs per square foot associated with higher-cost, more modern greenhouse facilities. Thus, growers should consider the gains in efficiency and their influences on CF, variable costs (and overhead costs) when making future decisions regarding investment in greenhouse structures.

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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.