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- Author or Editor: Dewayne Ingram x
Seeds of Sophora secundiflora (Ort.) Lag ex. DC. (mescal bean) were scarified with hot water or concentrated sulfuric acid to determine an optimal pretreatment for successful germination. Scanning electron micrographs indicated that the acid scarification treatment removed the seed cuticle. One-year-old seeds were successfully stored and germinated ≈2 days sooner than from the current year if both were given an acid pretreatment. Germination rate increased as acid pretreatment time increased from 30 to 120 minutes. Soaking seeds in water at room temperature or in hot water (initially 93C) for 24 hours had no effect on germination.
Root growth of southern magnolia (Magnolia grandiflora Hort. `St. Mary') was studied for 16 weeks after an 8-week exposure to 30, 34, 38, or 42 ± 0.8C root-zone temperature (RZT) treatments applied for 6 hours daily. Immediately after RZT treatments, total root length of trees responded negatively to increased RZT in a quadratic pattern and the shoot and root dry weight of trees was similar. However, 8 and 16 weeks after RZT treatments, total root length responded linearly in a negative pattern to increased RZT, and shoot and root dry weight responded negatively to increased RZT in a linear and quadratic pattern, respectively. Root dry weight of trees exposed to 42C RZT treatment was 29% and 48% less than 38 and 34C RZT treatments, respectively, at week 8. By week 16, root dry weight as a function of RZT had changed such that the 42C RZT was 43% and 47% less than 38 and 34C RZT, respectively. Differences in root growth patterns between weeks 8 and 16 suggest that trees were able to overcome the detrimental effects of the 38C treatment, whereas growth suppression by the 42C treatment was still evident after 16 weeks.
Abstract
Electrolyte leakage was used to measure direct heat injury to roots of Illicium anisatum L., Ilex cornuta L. cv. Burfordii and Juniperus chinensis L. cv. Parsonii. A sigmoidal relationship was found between percent electrolyte leakage and temperature treatment. About 50% electrolyte leakage was realized from a 20 minute exposure of roots to 50.5 ± 0.5°, 48.5 ± 0.5° and 46.5 ± 0.5°C for I. anisatum, J. chinensis, and I. cornuta, respectively.
Abstract
Root systems of Pittosporum tobira Thunb. plants were exposed to temperatures of 27°, 30°, or 40°C for 6 hours daily for 7 months. Top and root growth, root carbohydrate levels and photosynthetic rates were reduced by the 40° treatment. Content of K, Fe, and Zn in leaf tissues were reduced at highest root temperatures, while N content showed the opposite response.
Abstract
‘Mrs. G.G. Gerbing’ azaleas (Rhododendron L.), grown 12 months in a 2 pine bark : 1 Canadian peat : 1 sand (by volume) medium in 3-liter containers and fertilized with Woodace 14N-1P-2K compressed fertilizer tablets, had greater shoot and root dry weights if the medium was not amended with dolomitic limestone, compared to plants grown in the medium amended with dolomitic limestone at 3 kg/m3. Shoot and root dry weights were not different for plants grown with or without a superphosphate (9% P) amendment at 3 kg/m3 in combination with or without the dolomitic limestone amendment. Growing-medium Mn levels were greater (0.5 ppm) without the dolomitic limestone amendment, than with the amendment (0.06 ppm), whereas P levels were similar with or without the dolomitic limestone amendment. On day 60, growing-medium P levels were greatest (10 ppm) for the superphosphate-amended medium without dolomitic limestone and decreased to 0.5 ppm on day 300. Tissue P levels were not different with or without the superphosphate amendment in combination with or without dolomitic limestone.
Abstract
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.
Leaf photosynthesis of Magnolia grandiflora `St. Mary' (13-month-old rooted cuttings) was studied when tree roots were exposed to 28, 35, or 42 ± 0.8C for 8 weeks. Root-zone temperature (RZT) treatments were sustained for 6 hours per day by an electronically controlled root-heating system. The experiment was conducted in a 3×7.5-m walk-in growth room. Growth room irradiance was supplied by eighteen 1000-W, phosphor-coated metal-arc HID lamps (photosynthetic photon flux = 600 μpmol-2·-1 at canopy height) for 13 hours daily augmented with 3 hours of incandescent light during the dark period. Leaf C assimilation (A) at an RZT of 42C decreased linearly over 8 weeks compared to leaf A at RZTs of 35 and 28C. Leaf A was similar for all trees at week 1; however, leaf A at an RZT of 42C was 30% and 34% less than at RZTs of 3.5 and 28C, respectively, at week 8. Stomatal conductance at RZTs of 28 and 35C increased linearly over 8 weeks compared to conductance at a RZT of 42C. Intercellular CO2 levels were not affected by RZT treatments. This finding suggests that reductions in leaf A were nonstomatal. Photosynthetic inhibition resulted in reduced shoot and root growth. Operators of outdoor container production nurseries should implement cultural practices that minimize exposure of tree roots to RZTs >35C.
Computer modeling was used to study the effect of container volume and shape on summer temperature patterns for black polyethylene nursery containers filled with a 4 pine bark: 1 sand (v/v) rooting medium and located in Phoenix, Ariz. (lat. 33.5°N, long. 112°W) or Lexington, Ky. (lat. 38.0°N, long. 84.4°W). For both locations, medium temperatures were highest at the east and west container walls, halfway down the container profile, regardless of container height (20 to 50 cm) or volume (10 to 70 liters). The daily maximum medium temperature (Tmax) at the center was lower and occurred later in the day as container volume was increased because of an increased distance to the container wall. For both locations, predicted temperature patterns in rooting medium adjacent to the container wall decreased as the wall tilt angle (TA) increased. Predicted temperature patterns at the center of the container profile were lowered in response to the interaction of increased container height and wall TA. As container height decreased, the container wall TA necessary to lower center Tmax to ≤ 40C increased; however, the required increase in TA was greater for Phoenix than for Lexington, principally because of higher ambient air temperatures.
This research uses a life cycle analysis and economic engineering approach to determine the costs and global warming potential (GWP) of production and post-production practices associated with Taxus ×media ‘Densiformis’, which is often grown using a more capital-intensive regime during the propagative and harvesting stages than the typical field-grown shrub. Total variable costs incurred during the rooted cutting stage were slightly over $0.24 per marketable rooted cutting. This was made up of $0.1966, $0.032, and $0.0127 for labor, materials, and equipment operating costs, respectively. The GWP of materials and equipment used during the rooted cutting stage of production was 0.0097 and 0.2762 kg CO2 equivalent (CO2e), respectively. Equipment costs in this phase were predominantly from heating the greenhouse (92%) and the greenhouse heating functions comprised 95% of the rooting cutting GWP. GWP during the post-farm gate stage was 2.4506 kg CO2e per marketable shrub but was offset by 12.5522 kg CO2 being sequestered in the shrub during its time in the landscape and weighted over the 100-year assessment period, leaving a net GWP of –8.1824 kg CO2e per marketable shrub by the end of the life cycle. Total takedown and disposal costs (labor) after an assumed 50-year life in the landscape were $9.0610. During the entire life cycle from cutting to landscape to takedown and disposal, total variable costs incurred were $17.9856 per shrub. These findings are consistent with previous studies in that the GWP is positive when considering the entire life cycle of the shrub from propagation to eventual removal from the landscape. Knowing the carbon footprint of production and distribution components of field-grown shrubs will help nursery managers understand the environmental costs associated with their respective systems and evaluate potential system modifications to reduce greenhouse gas (GHG) emissions.
System-level research has resulted in significant advancements in horticultural crop production. Contributions of individual components to production efficiency, cost, and environmental impact have been a focus of such research. Public awareness of the environmental impact of products and services is increasing. Life cycle assessment (LCA) is a tool to study horticultural crop production systems and horticultural services and their individual components on environmental impacts such as the carbon footprint, stated as global warming potential. This manuscript introduces LCA and describes how this tool can be used to generate information important to the industry and consuming public.