University researchers have recently quantified the value of carbon sequestration provided by landscape trees (, ). However, no study to date has captured the economic costs of component horticultural systems while conducting a life cycle assessment of any green industry product. This study attempts to fill that void. The nursery production system modeled in this study was a field-grown, 5-cm (2-in) caliper Cercis canadensis ‘Forest Pansy’ in the Lower Midwest. Partial budgeting modeling procedures were also used to measure the sensitivity of related costs and potential benefits associated with short-run changes in cultural practices in the production systems analyzed (e.g., transport distance, post-harvest activities, fertilization rates, and plant mortality). Total variable costs for the seedling and liner stages combined amounted to $2.93 per liner, including $1.92 per liner for labor, $0.73 for materials, and $0.27 per liner for equipment use. The global warming potential (GWP) associated with the seedling and liner stages combined included 0.3123 kg of carbon dioxide equivalents (CO2e) for materials and 0.2228 kg CO2e for equipment use. Total farm-gate variable costs (the seedling, liner, and field production phases combined) amounted to $37.74 per marketable tree, comprised of $9.90 for labor, $21.11 for materials, and $6.73 for equipment use, respectively. However, post-harvest costs (e.g., transportation, transplanting, take-down, and disposal costs) added another $33.78 in labor costs and $27.08 in equipment costs to the farm-gate cost, yielding a total cost from seedling to end of tree life of $98.60. Of this, $43.68 was spent on labor, $21.11 spent on materials, and $33.81 spent on equipment use during the life cycle of each marketable tree. As per an earlier study, the life cycle GWP of the described redbud tree, including greenhouse gas emissions during production, transport, transplanting, take-down, and disposal, would be a negative 63 kg CO2e (). These combined data can be used to communicate to the consuming public the true (positive) value of trees in the landscape.
Fertilizer is the 2nd largest supply item purchased by commercial nurseries (1). The cost of fertilizer and labor for application has been estimated as 11% of production costs for a container nursery (2). Although fertilization (fertilizer and labor) costs are a small part of production costs, they are manageable. Thus, the ability to calculate fertilization cost accurately and rapidly assists the nursery operator in making timely management decisions. A microcomputer program was developed to calculate fertilization cost per container for one or combinations of the following methods of fertilizer application (MOA): broadcast, incorporation, injection, and top-dress.
Roots of sour orange (Citrus aurantium L.), ‘Carrizo’ citrange [C. sinensis L. (Osbeck.) × Poncirus trifoliata L. (Raf.)] and ‘Swingle’ citrumelo [C. paradisi Macf. × P. trifoliata L. (Raf.)] seedlings were exposed to various high temperatures for 20 minutes and heat injury was determined by electrolyte leakage procedures, microscopic examination, and visual observations. Temperatures at the midpoint of sigmoidal curves fitted through electrolyte leakage data for excised roots were 51.6° ± 0.5°C, 52.5° ± 0.7°, and 53.5° ± 0.5° for ‘Carrizo’ citrange, sour orange, and ‘Swingle’ citrumelo rootstocks, respectively. Electrolyte leakage results with excised roots were supported by microscopic examination and visual observations of whole plants.
Juniperus horizontalis ‘Andorra Compacta’ and Rhododendron simsii ‘Redwing’ were grown for 6 months in 3 media to evaluate selected nutrient sources at 2 lime levels. Sulfur-coated urea (SCU) induced the lowest final medium pH, and isobutylidene diurea (IBDU) induced the highest. Lime application to the 2 Canadian peat : 1 calcined clay medium (v/v) was detrimental to ‘Redwing’ azalea shoot growth. Nutrient source did not affect shoot or root growth of azaleas growing in the 2 pine bark : 1 sand medium (v/v). In general, SCU produced more azalea shoot and root growth than the other nutrient sources. Liming decreased juniper shoot growth in the 1 pine bark : 1 Canadian peat : 1 sand medium (by volume). Oxamide and Osmocote produced significantly more juniper shoot growth in the pine bark : sand and pine bark : Canadian peat : sand media than other nutrient sources. After 6 months, plants fertilized with either IBDU or SCU had a higher concentration of leaf N than did those fertilized with Osmocote (18N–2.6P–10K).
The addition of peat-perlite to backfill soil increased the initial root movement through the backfill of transplanted holly (Ilex crenata Thunb. cv. Green Luster) grown in a peat-perlite medium. Backfill composition had no effect on the initial movement of roots of plants grown in a soil-peat-sand or pine bark-sand medium.
Stem caliper and sum of lateral branch lengths of container-grown Quercus shumardii seedlings increased more in 13 months when fertilized with 75:25, 50:50, 25:75 and 100:0 (NH4:NO3) ratios than with 100% NO3-N, regardless of fertilization rate. Stem caliper increased as fertilization rate increased from 5.7 to 11.4 g N/container yr. Height was unaffected by NH4:NO3 ratio or fertilization rate. Chlorosis was evident on plants that received 50% or more NO3-N. Media pH decreased with increasing NH4- N, and leaf N concentration increased from 1.16% with 100% NO3-N to 1.57% with 100% NH4-N.
Stage 2 micropropagules were transferred into woody plant medium supplemented with either 0, 0.1, 1, 10, 100 mg/L ABA (Abscisic acid) and with or without 1 mg/L IBA (Indole-3-butyric acid), Significant decreases in total dry weight and shoot length were observed at 1, 10 and 100 mg/L of ABA regardless of IBA concentration, Leaf area was significantly reduced in all treatments by increasing ABA levels. In the absence of IBA no callus formed but lateral roots developed. Another experiment using ABA levels of 0, 0.1, 0.5 and 0, 1 mg/L IBA was conducted. Total number of roots decreased with increasing ABA levels. Adventitious roots which formed on the stem and roots originating from root primordia were observed in all ABA levels with IBA, Callus did not form in the treatments lacking IBA. Scanning electron microscopy was used to document morphological differences due to ABA, Abscisic acid levels in leaf tissue were assayed using immunological techniques.
Although controlled-release fertilizers (CRFs) have been used in container-grown ornamental plants for decades, new coating technologies and blends of fertilizers coated for specific release rates are being employed to customize fertility for specific environments and crops. A study was conducted in the transitional climate of Kentucky to determine the nutrient release rates of three controlled-release blends of 8- to 9-month release and growth response of ‘Double Play Pink’ japanese spirea (Spiraea japonica) and ‘Smaragd’ arbovitae (Thuja occidentalis). Fertilizer 1 (16N–3.5P–8.3K–1.8Mg + trace elements) and Fertilizer 2 (18N–3.1P–8.3K–1.8Mg + trace elements) were prototype blends with different experimental polymer coatings. Fertilizer 3 was a blend of 18N–2.2P–6.6K–1.1Ca–1.4Mg–5.8S + trace elements, which combined 100% resin-coated prills with a polymer coating. Fertilizer 4 was commercially available 15N–3.9P–10K–1.3Mg–6S + trace elements. Fertilizer 3 released its nutrients earlier in the 12-week study than the other three fertilizers and resulted in lower shoot dry weight in both species. The new polymer coating technologies show promise for delivering a predicted release rate and are appropriate for container production of these woody shrubs in Kentucky. An interesting side note of this experiment was that leachate pH measurements across treatments averaged 1.2 units lower for arbovitae (6.3) than for japanese spirea (7.5) at week 12. It was assumed that chemical and/or biological reactions at the root/substrate interface in arbovitae moderated pH increases over the study.
Direct heat injury to plant parts may occur in areas of high insolation and high humidity where transpiration is low. Using electrolyte leakage procedures, critical high temperatures of detached leaves of ‘Glen’ citrange [Citrus sinensis L. (Osbk.) × Poncirus trifoliata L. (Raf.)], ‘Swingle’ citrumelo [C. paradisi Macf. × P. trifoliata L. (Raf.)], and ‘Hamlin’ orange [C. sinensis L. (Osbk.)] were determined by exposure to temperatures between 25° and 65°C. Lethal temperatures for a 20 min exposure ranged from 54.3° ± 0.5° for ‘Glen’ citrange to 56.1° ± 0.4° for ‘Swingle’ citrumelo. Maximum canopy temperatures of 36.6° were recorded. Therefore, it appears that under field conditions in Florida, these cultivars are normally not subjected to temperatures that would cause direct heat injury.
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.