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Browsing by Author "Wright, Robert D."

Now showing 1 - 16 of 16
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    Characterization of water stress during cold storage and establishment for Acer platanoides and Crataegus phaenopyrum
    Bates, Ricky Martin (Virginia Tech, 1994-08-01)
    This study examined the affects of desiccation during and after cold storage on the physiology, growth, and marketability of bare-root Acer platanoides (Norway maple), Crataegus phaenopyrum (Washington hawthorn) and Prunus x yedoensis (Yoshino cherry). Histological examination of Acer and Crataegus stems was also conducted. Maple and cherry trees were transplanted into pine bark-filled containers and subjected to mist or non-mist treatments. Xylem water potential increased (became less negative) for misted maple and cherry trees. Water potential increased for non-misted maple and decreased for non-misted cherry trees. Maple and hawthorn seedlings were subjected to cold storage durations of 2, 4, 6, 8, 10, and 12 weeks and storage treatments: whole plant covered, shoots exposed, roots exposed and whole plant exposed. Shoot (Ψs) and root (Ψr) water potentials for all treatments and both species decreased during storage. For maple, (Ψs) and (Ψr) of the exposed shoot treatment were the same as the whole plant covered treatment. In contrast, hawthorn (Ψs) and (Ψr) of the exposed shoot treatment were lower (more negative) than for the whole plant covered treatment. Root hydraulic conductivity was the same for both species and decreased with increased storage duration and for treatments with exposed roots. For the root covered treatments, maple root growth potential (RGP) increased while hawthorn RGP decreased with increased cold storage duration. RGP for both species remained low throughout storage for treatments exposing roots. Days to bud break for Acer and Crataegus seedlings decreased with increased storage time for the whole plant covered treatments but increased for both species when stored with exposed roots. Maple marketability, percent of trees with ≤ 10% shoot dieback, for root covered treatments was high for most storage durations. Hawthorn marketability was generally low except for the whole plant covered treatment during the first six weeks of storage. There was a high positive correlation between RGP and marketability for both maple and hawthorn. Histological examination revealed that Acer stems had a highly suberized periderm, and a uniform cuticle with few disruptions. Periderm suberization of Crataegus stems was variable and extensive peridermal cracking was evident. Cuticle wax decreased with increasing distance from the stem apex for both species. Collectively, results indicated that hawthorn stems had more pathways for water loss than maple shoots. While protection of roots of all bare-root stock is important, desiccation sensitive species such as Washington hawthorn require both root and shoot protection during storage and at transplanting to minimize water loss.
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    Chemical, Physical, and Biological Factors Influencing Nutrient Availability and Plant Growth in a Pine Tree Substrate
    Jackson, Brian Eugene (Virginia Tech, 2008-10-24)
    Pine tree substrate (PTS) produced from freshly harvested loblolly pine (Pinus taeda L.) trees has potential for replacing or reducing the use of aged pine bark (PB) and peat moss as container substrates for horticulture crop production. The objective of this work was to determine the factors influencing nutrient availability in PTS compared to PB or peat substrates. Chapter two reports data on the response of japanese holly and azalea to fertilizer rate when grown in PTS and PB. This study demonstrated that an additional 2.4 kg·m-3 of Osmocote Plus (15N-3.9P-10K) controlled release fertilizer is required for both species when grown in PTS compared to PB. Data are reported in chapter three on the effects of fertilizer rate, substrate particle size, and peat amendment on growth and floral quality, and on post-production time-to-wilting of poinsettias. Data from this work show that PTS requires an additional 100 mg·L-1 N to grow poinsettias comparable to plants grown in peat unless the particle size of PTS was decreased or 25% peat was added, in which case no additional fertilizer was needed. Results also indicated that PTS shrinkage was similar to that of peat, and that post-production time-to-wilting in PTS plants was similar as plants grown in peat. Data in chapter four compares nitrogen (N) immobilization rates, substrate carbon dioxide (CO₂) efflux levels, and nutrient leaching in peat, PB, and PTS over time. Data from these studies indicated that more N immobilization occurs in PTS than in PB or peat and that the substrate CO₂ efflux levels (estimate of microbial activity) corresponds to N immobilization in all substrates. Nutrient availability, changes in physical and chemical properties, substrate shrinkage, and microbial activity in PTS compared to PB during long-term nursery production are reported in chapter five. Results showed that substrate nutrient levels remain lower in PTS and that pH levels of PTS decrease considerably over two growing seasons compared to PB. Results also indicate that PTS does decompose over time in containers, but substrate shrinkage of PTS is similar to that of PL and PB during crop production.
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    Chipped wood as a substrate for plant growth
    (United States Patent and Trademark Office, 2007-01-23)
    The present invention provides compositions comprising chipped whole wood logs as a substrate for growth of plants. It further provides a method of making a substrate comprising wood chips for growth of plants, and a method of growing potted plants in a composition comprising chipped wood logs as the primary substrate for growth.
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    Effect of Micronutrient Rate on the Growth of Containerized Quercus palustris Seddlings in Pine Bark
    Kelk, Lisa (Virginia Tech, 2002-09-09)
    The objectives for this research were to determine: 1) the rate of Micromax which will produce maximum growth of pin oak (Quercus palustris Munchh.), a landscape tree which has shown a previous growth response to the addition of Micromax at the manufacturer's recommended rate, 2) which micronutrient(s) is most associated with maximum growth, and 3) the rate of Cu, Fe, Mn, and Zn required to produce maximum growth of Quercus palustris. Q. palustris seedlings were container-grown in pine bark amended with the following rates of Micromax: 0, 0.15, 0.3, 0.6, 0.9, 1.8, or 2.7 kg(m-3 in 2000, 2001, and 2002. For all three years, the maximum growth was obtained at rates near the manufacturer's recommended rate of 0.9 kg(m-3. A micronutrient mix was formulated by increasing the levels of Zn, Mn, Fe, and Cu individually while holding the other micronutrients constant based on the grams of each micronutrient contained in Micromax at 0, 0.15, 0.3, 0.6, 0.9, 1.8, or 2.7 kg(m-3 for 2001 and 0, 0.45, 0.9, or 1.8 kg(m-3 for 2002. In addition, Cu, Fe, Mn, and Zn were also applied alone to pine bark at rates of 0, 0.45, 0.9, or 1.8 kg(m-3 without the addition of any other micronutrients. Holding all other micronutrients constant and increasing the rate of one micronutrient did not increase growth. However, when Cu, Fe, Mn, or Zn was added to pine bark alone at increasing rates, growth increased. For Cu and Zn, the growth increased was linear suggesting that a higher rate of Cu and Zn than that provided by Micromax at the manufacturer's recommended rate might be advantageous.
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    The effects of growth medium acidity, exogenous growth regulators, and nitrogen fertilizer on the acceleration of Fraser fir seedling growth
    Bryan, James Alfred (Virginia Tech, 1988-08-05)
    Three factors were tested in an attempt to accelerate the growth of Abies fraseri seedlings grown in containers in a greenhouse: growth medium acidity. foliar application of growth regulators. and supply of nitrogen fertilizer. Sphagnum peat growth medium was adjusted with a to 8 kg dolomitic limestone/m3 compressed packaged peat to initial pH ranging from 3.9 to 6.7. Best growth (21.2 cm mean height at 19 months) was achieved with 1 kg/m³ and 2 kg/m³â ¢ with initial mean pH 4.2 and 4.5. respectively. Seedlings with 4 and 8 kg/m³ grew more slowly (17.4 and 9.5 cm. respectively. in 19 months). and many were chlorotic. with poor root development. Three growth regulators were sprayed on seedlings: benzylaminopurine (BAP). gibberellic acid (G~. and indolebutyric acid (IBA). BAP stimulated terminal bud activity. decreasing the periods of rest between active growth. BAP increased height and diameter of new shoot growth up to 19% and 32% respectively. BAP reduced root growth 22% when applied at the higher concentration (100 ppm). GA3 had no main effect on either shoot or root growth. However. GA3 did increase shoot growth slightly in the absence of BAP. IBA increased root growth up to 26%. IBA had no significant effect on shoot growth. Nitrogen fertilizer was supplied weekly in concentrations of 200. 400. and 600 ppm. At six months age there was no treatment effect on seedling growth. At nine months age 400 ppm N had produced 9% more shoot growth than either 200 or 600 ppm N. Nine-month-old seedlings with 400 ppm fertilizer averaged 8.9 cm in height.
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    Effects of Transplant Season and Container Size on Landscape Establishment of Kalmia latifolia L.
    Hanson, Anne-Marie (Virginia Tech, 2002-05-03)
    Mountain laurel (Kalmia latifolia L.) is relatively difficult to establish in landscapes. One experiment tested the effect of container size on the water relations of pinebark substrate embedded in field soil. Two other experiments tested the effects of transplant season and container size on landscape establishment of nursery-produced mountain laurel. Experiment one compared volumetric water content of embedded substrate of five sizes (4-L to 100-L) to adjacent field soil at two depths with time domain reflectometry (TDR) during a dry down cycle. Available water was calculated by subtracting unavailable water (estimated with pressure plates) from volumetric water content (TDR measurements). Adjacent soil contained more available water than embedded substrate. The middle depth held more water than the top. Larger pinebark substrate volumes retained higher volumetric water content than smaller volumes. The second experiment consisted of 7.6- and 19-L containers of Kalmia latifolia L. ‘Olympic Wedding’, transplanted into field soil in October or May. Larger container plants generally had lower xylem potential than smaller plants, but better visual ratings. Root growth into surrounding soil was negligible for all treatments. Leaf area was higher for spring transplants than fall transplants. Experiment three was a rhizotron study with 19-L plants, transplanted in October or May. Canopy growth of spring transplants was greater than fall transplants, but fall transplants had longer roots into the backfill. Overall, our data suggest that fall transplanting will potentially allow faster plant establishment than spring transplanting. The effect of container size on plant establishment could not be determined.
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    Influence of Temperature and Time on Nutrient Release Patterns of Osmocote Plus™, Nutricote™, and Polyon™ Controlled-Release Fertilizers
    Husby, Chad Eric (Virginia Tech, 2000-06-15)
    Polymer-coated controlled-release fertilizers (PCFs) are the most widely used class of fertilizers in the production of container-grown nursery plants. Nutrient release from PCFs is primarily influenced by temperature. The objective of this study was to determine the influences of temperature and time on the nutrient release patterns of three PCFs (each with a rated longevity of 8-9 months), each using a different coating technology: Osmocote Plus™ 15N-3.93P-9.96K, Polyon™ 18N-2.62P-9.96K, and Nutricote™ 18N-2.62P-6.64K. The first three experiments investigated the effects of time on long-term nutrient release. In Expt. 1, each of the three PCFs were placed in flasks of distilled water maintained at 40°C for 22 weeks. Fertilizer solutions were poured off at bi-weekly intervals and measured for electrical conductivity (EC) and NO3-N, NH4-N, P, K, Fe, Mn, Cu, and Zn concentrations. Overall, nutrient release for the three PCFs was higher and more variable in the first eight weeks than later in the experiment. Polyon's™ macronutrient release was generally more gradual than that of the other products. Micronutrient release patterns varied substantially between fertilizers and nutrients. In Expt. 2, pine bark (PB)-filled containers were amended with the three PCFs and irrigated regularly in a greenhouse. PCFs were removed from containers when Osmocote Plus'™ NO₃-N supply was ~66% expended and analyzed for EC, NO₃-N, NH₄-N, and P concentration. Except for P, the percentage of each nutrient remaining was roughly comparable to those remaining at the corresponding stage of Expt. 1, suggesting that PCF nutrient release behavior in the laboratory method is comparable with nutrient release behavior in PB in the greenhouse. At the end of Expts. 1 and 2, Osmocote Plus™ had expended a higher percentage of its nutrients than the other fertilizers. In Expt. 3, substrate solutions were collected weekly from PB-filled containers (same treatments as in Expt. 2) and EC was determined. The substrate solution EC of Osmocote Plus™-fertilized PB began to decline sooner than that of the other fertilizers. Overall, these three experiments led to the conclusion that Osmocote Plus™ nutrient release declines more quickly than does Polyon™ or Nutricote™, while Polyon™ has the most gradual nutrient release pattern. The objective of the second set of experiments was to determine the effects of temperature on short-term nutrient release. In Expt. 4, 14 g of each PCF was maintained at 40°C until ~33% of the NO3-N content in Osmocote Plus™ was expended. Each fertilizer was then placed in a sand column and leached with distilled water at ~100 mL/h. Columns were then incrementally subjected to a simulated diurnal container temperature change from 20°C to 40°C and back to 20°C over a period of 20 h. Leachate was collected hourly and measured for soluble salts and NO₃-N and NH₄-N concentrations. For all fertilizers, nutrient release increased and decreased with the respective increase and decrease in temperature. Nutrient release patterns of the three fertilizers were significantly different, with Osmocote Plus™ showing the greatest overall change in nutrient release between 20°C and 40°C and Nutricote™ the least. In Expt. 5, PCFs were placed in flasks of distilled water in constant temperature baths. Initially, fertilizers were held at 40°C for three days and then at temperatures of 22, 28, 34, or 40°C for two weeks. Fertilizer solutions were poured off after the first and second weeks. Only solutions from the second week were analyzed for soluble salts and NO₃-N, NH₄-N, P, and K concentrations. For Osmocote Plus™ and Polyon™, there was a 29% to 86% (depending on the nutrient measured) mean increase in nutrient release between 22°C and 40°C, whereas for Nutricote™ there was a 345% to 364% (depending on the nutrient measured) mean increase. The overall mean increases in nutrient release in Expt. 4 were between 1032% and 4023%, whereas the mean increases in Expt. 5 were between 29% and 364%. In summary, the second set of experiments found that PCF nutrient release was highly sensitive to diurnal temperature changes.
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    Influence of Transplanting Practices on Growth and Embolism Levels For Urban Tree Species
    Knight, Patricia Rene (Virginia Tech, 1997-03-31)
    Changes in xylem embolism levels due to drought stress or freezing have been documented for a wide variety of plants. High degrees of tissue water stress which lead to increased levels of embolism are also often cited as factors negatively influencing plant establishment. Embolized xylem elements can potentially lead to restriction of stem water flow, thereby reducing growth. Therefore, this dissertation (5 experiments) was undertaken to determine if certain transplanting practices affect embolism dynamics and plant growth of selected urban tree species. Embolism was estimated based on reductions in hydraulic conductance of harvested stem segments. An initial experiment determined the length of time from tissue harvest to embolism measurement that stem samples may be held in cold storage. Results varied between Fraxinus americana L. (white ash) and Acer rubrum L. x saccharinum L. (hybrid red maple), but data suggested white ash stem samples should not be stored more than one day, especially for between-species comparisons. A greenhouse experiment investigated the growth and embolism levels for container-grown Corylus colurna L. (Turkish hazelnut) seedlings in response to root pruning. Increasing levels of root pruning from 25 to 50% increased embolism, although plant height also increased. There was no fertilizer level x root pruning interaction for embolism. A field-harvest and greenhouse growth experiment investigated the influence of cold storage duration on plant growth and pre- and post-transplant embolism levels. Embolism levels increased with duration of cold storage for Acer rubrum L. (red maple), but not for Crataegus phaenopyrum (L.f.) Medic. (Washington hawthorn). After 15 weeks of growth, however, embolism levels were similar for both species. Growth increased with increased cold storage duration for both species. A field experiment investigated the influence of transplant season and root pruning on plant growth and embolism of Turkish hazelnut and Syringa reticulata (Blume) Hara (tree lilac). Embolism levels just prior to budbreak and days to budbreak were highest for fall-transplanted Turkish hazelnut. Embolism level was unaffected by treatments. No clear relationship between embolism and growth could be determined for either species the first season after transplanting. Other fall-transplanted Turkish hazelnuts, however, had growth reductions that corresponded to increasing embolism levels two years after transplanting. An additional transplanting experiment examined the influence of root severance at transplanting on water relations of red maple. Stem sap flow (in vivo) was reduced within 2 h of harvest, and leaf stomatal conductance was reduced 4 h after harvest. Percent embolism (in vitro) was increased within 24 hr of harvest. Results of these experiments indicate that root pruning, and choice of transplant season can reduce plant growth and increase embolism levels. No clear relationship between embolism and growth reduction was evident. Although embolism dynamics are clearly impacted by transplanting, the implications for transplant success are inconclusive. The role of embolism in transplant success was not clear.
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    Monitoring Nutrients in Large Nursery Containers
    Wright, Robert D.; Stanley, Mary H. (Virginia Cooperative Extension, 2009-05-01)
    Explains how to properly use a suction-cup lysimeter, soil sampler, to extract the substrate solution from large containers in order to take electrical conductivity, pH, and nutrient analyses.
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    Overcoming Summer Dormancy of Boxwood
    Musselwhite, Sheri Ruth (Virginia Tech, 2002-05-15)
    The objective of this work was to determine if summer dormancy of boxwood could be removed either through nutritional or hormonal means. Buxus sempervirens L. "Suffruticosa", B. sempervirens "Vardar Valley", and B sinica var. insularis (Nakai) "Justin Brouwers" were used for these studies. In the nutrition study, experiments were conducted to examine the effects of various levels of Osmocote 15-9-12 and liquid 10-4-6 on growth of boxwood. Optimal shoot dry weight was achieved at applications of 12 to 16 g Osmocote and 100 – 150 ppm N liquid fertilizer. Leachate EC corresponding to optimal shoot dry weight ranged from 0.5 to 0.7 dS/m for Osmocote and from 0.7 to 1.5 dS/m for liquid fertilizer. While the fertilizer requirements for boxwood optimal dry weight accumulation were determined, additional flushes of growth subsequent to the initial spring flush did not occur for "Vardar Valley" and English boxwood. In the phytohormone study, experiments were conducted that examined the effects of pruning, Promalin (GA4+7 and BA), and defoliation on the growth of three boxwood species. While Promalin applied alone or in conjunction with pruning shows promise of increasing new shoot growth, its response was not consistent from experiment to experiment. In fact, when it was applied in conjunction with defoliation, it dramatically decreased number of new shoots and actually resulted in some shoot mortality. Pruning was also erratic in its promotion of new shoots. Defoliation increased new shoot number dramatically and shows the most promise in overcoming summer dormancy.
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    Some aspects of nitrogen nutrition on selected Ilex
    Gilliam, Charles Homer (Virginia Tech, 1977-09-05)
    Three holly cultivars, Ilex crenata, Thunb. 'Helleri' and 'Rotundifolia' and Ilex cornuta Lindl. et Paxt. 'Burfordi' were grown in 3 liter containers at 200, 300, 400 and 500 ppm nitrogen (N). Significant correlation coefficients were found between plant growth (dry wt accumulation) and both leaf N content and soil solution nitrates, while low correlation coefficients were found between soil nitrates and plant growth. Shoot growth of 'Helleri' and 'Burfordi' was not increased by N levels higher than 300 ppm while 400 ppm N was optimal for 'Rotundifolia'. The effects of 3N levels on tissue N fluctuations during a flush of growth on 'Helleri' were also studied. For all N levels, tissue N levels were shown to increase following the cessation of stem elongation until a level of tissue N was reached where a new flush of growth began. These N levels were approx the same for all N treatments. The time necessary to reach this level was dependent on the level of N added; 5 weeks for 300 ppm, 13 weeks for 150 ppm and 18 weeks for 50 ppm N. Once new growth began, tissue N levels began to decrease. The response of 'Helleri' to 15 fertilizer treatments consisting of different time and lengths was studied. Fertilizer applied during a period following the cessation of stem elongation and before the next flush resulted in greater total N and shoot growth, regardless of whether it was also applied during other weeks or not. Root growth was suppressed by 3 or more fertilizer applications, regardless of the time of application.
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    Spray stake irrigation of container-grown plants
    Lamack, William F. (Virginia Tech, 1992-04-05)
    Studies were conducted to evaluate the effect of pre-irrigation media moisture deficit, irrigation application rate, and intermittent irrigation on irrigation efficiency [(amount applied - amount leached) amount applied' 100] of spray stake-irrigated, container-grown plants. In the first experiment, pine bark-filled containers were irrigated to replace moisture deficits of 600, 1200, or 1800 ml. Deficits were returned in single, continuous applications at application rates of 148, 220, and 270 ml/min. Application rate did not affect irrigation efficiency. Efficiency decreased with increased medium moisture deficit. In the second experiment, containers, at 600 ml media moisture deficits, were irrigated with 400 or 600 ml (65% and 100% water replacement, respectively). Irrigation volumes were returned in a single, continuous application or in 100ml applications with 30 min intervals between irrigations (intermittent). Irrigation efficiency was greater with intermittent irrigation, 95 % and 84 % for 400 and 600 ml replacement, respectively, than with continuous irrigation, 84% and 67% for 400 and 600 ml replacement, respectively. When applied intermittently, most water loss from containers occurred after 400 ml were applied. In the third experiment, containers were irrigated with 600 ml (100% water replacement) in 50, 100, or 150 ml applications with 20, 40, or 60 min intelVals between applications. A control was included in which 600 ml was applied in a single, continuous application. Irrigation efficiency increased with decreasing application volume and increasing length of interval between applications. The greatest efficiency (86%) was produced with an irrigation regimen of 50 ml applications with at least 40 min between applications. The control treatment (continuous) produced an irrigation efficiency of 62%. When applied intermittently, most water loss from containers occurred after a total of 300 ml were applied.
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    Storage of Pine Tree Substrate Influences Plant Growth, Nitrification, and Substrate Properties
    Taylor, Linda Lea (Virginia Tech, 2011-10-28)
    Pine tree substrate (PTS) is a relatively new substrate for container crop production. There are no detailed studies that elucidate how storage time impacts PTS chemical, physical, and biological aspects. The objective of this research was to determine how PTS storage time influenced PTS chemical and physical properties, nitrification, and plant growth. Pine tree substrate was manufactured by hammer-milling chips of loblolly pine trees (Pinus taeda L.) through two screen sizes, 4.76 mm (PTS) and 15.9 mm amended with peat (PTSP). PTS and PTSP were amended with lime at five rates. A peat-perlite mix (PL) served as a control treatment. Prepared substrates were placed in storage bags and stored in an open shed in Blacksburg, Virginia. Subsamples were taken at 1, 42, 84, 168, 270, and 365 days. At each subsampling day, twelve 1-L containers were filled with each substrate. Six containers were left fallow and six were planted with marigold (Tagetes erecta L. "Inca Gold") seedlings. Substrate was also collected from select treatments for Most Probable Number assays to estimate density of nitrifying microorganisms, and for chemical and physical property analyses. Pour-through extracts were collected from fallow containers at 0, 2, and 4 weeks, and from marigold containers at harvest for determination of pH, electrical conductivity, ammonium-N and nitrate-N. At harvest, marigold height, width, and dry weight were measured. At least 1 kg·m-3 lime for PTS, and 2 to 4 kg·m-3 lime for PTSP were needed to maintain pH values ≥ 5.5 for 365 days. Bound acidity of unlimed PTS increased but cation exchange capacity for unlimed PTS and PTSP decreased over 365 days. Carbon to nitrogen ratio and bulk density values were unchanged over time in all treatments. There were minor changes in particle size distribution for limed PTS and unlimed and limed PTSP. Marigold growth in PTS and PTSP was ≥ PL in all limed treatments, except at day 1. Nitrite-oxidizing microorganisms were present and nitrification occurred in PTS and PTSP at all subsampling days. Pine tree substrate is relatively stable in storage, but pH decreases, and lime addition may be necessary to offset this decrease.
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    Suction Cup Lysimeter Method for Extracting Pine Bark Substrate Solution
    Stanley, Mary H. (Virginia Tech, 2002-04-18)
    The objective of this study was to determine the effectiveness of suction cup lysimeters (SCL) in extracting substrate solution from pine bark substrates. Lysimeter types tested were 4.8-cm diameter with a ½ or 1-bar air-entry value (AEV) and 2.2-cm diameter also with a ½ or 1-bar AEV. Sufficient volume could be obtained when a vacuum pressure of 30, 40 or 50 cb was applied to lysimeters with a minimum extraction time of five minutes. The 2.2-cm lysimeters were found to be suitable for extracting solution if smaller sample volumes were needed. To determine effect of vacuum pressure and extraction time on volume extracted, the 4.8-cm ½-bar lysimeters were installed in containers with pine bark substrate and Quercus phellos L. (willow oak) trees. Volumes extracted were somewhat erratic and not strongly dependent upon centibars of vacuum or extraction time. Lysimeters immersed in water demonstrated that variability was not due to individual lysimeters, but to the coarse nature of the pine bark substrate. Substrate EC levels were not affected when volume of substrate solution extracted by the SCL's varied from 10 to190 ml.â To determine the effectiveness of SCL's to monitor nutrient status of container-grown shade trees, two-year-old container-grown willow oak trees were grown in a pine bark substrate and fertilized with 0, 50, 100, 150, 200, 250 or 300 grams Osmocote Plus Northern (15N – 3.9P – 9.8K). Plant height and trunk diameter increased with up to 200 grams of Osmocote per container. There was a good relationship between solution EC and plant growth
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    Sulfur Requirements of Container-grown Pin Oak and Japanese Maple
    Browder, Jake Forrest (Virginia Tech, 2004-11-19)
    The objectives for this research were to determine: 1) whether sulfated micronutrient addition increased growth of container-grown pin oak (Quercus palustris MuÌ nchh) and Japanese maple (Acer palmatum Thunb.) seedlings by supplying micronutrients, sulfur, or decreasing substrate pH, 2) S requirements of Q. palustris and A. palmatum container-grown in a pine bark (PB) substrate, and 3) if there are any conditions that will affect these S requirements. Container grown Q. palustris and A. palmatum seedlings were grown in PB, amended (or not) with the following treatments: control (no amendment), Micromax (commercial micronutrient fertilizer [sulfate form]), K2SO4, H2SO4, HCl, chelated micronutrients, elemental S, or CaSO4. Dry weights of plants in all treatments supplying S were higher than for plants receiving no S. These data indicate that S, not micronutrient application, was the primary cause of increased growth from the addition of sulfated micronutrients. In other experiments these two species were fertilized with 8 different concentrations of S application (0, 1, 2, 5, 10, 20, 40, or 80 mg·liter-1). Regression analysis revealed dry weights of both species were near maximum at the extrapolated application concentration of 30 mg·liter-1 S, which corresponded to approximately 15 and 7 mg·liter-1 S in substrate solution for oak and maple, respectively. In another set of experiments plants were fertilized with Micromax or FeSO4 with or without lime. In the plus lime treatments (substrate pH 6.1), plant dry weights were higher in Micromax fertilized plants than for FeSO4 fertilized plants. However, in the minus lime treatment (substrate pH 4.5), FeSO4 addition effectively supplied S to plants.
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    Water Use of Landscape Trees During Pot-In-Pot Production and During Establishment in the Landscape
    Witmer, Robert K. (Virginia Tech, 2000-12-04)
    Water conservation and pollution concerns from nutrient runoff will very likely dictate precise irrigation regimes for nursery managers in Virginia. Maximum plant growth with minimum input of water and fertilizer is becoming increasingly important. Therefore, water use and growth of red and sugar maple (Acer rubrum L. 'Franksred' and Acer saccharum Marsh.) were studied during two years of pot-in-pot (P+P) production and during three years after transplanting to field soil. Three major experiments were completed. The first experiment studied the effect of frequent irrigation (three-times-a-day) versus standard once-a-day irrigation and found that frequent irrigation increased trunk diameter growth of sugar maples in the second production cycle and for red maples in both production cycles. Height growth of neither species was affected by frequent irrigation. A study of sap flow pattern indicated that late day water stress of red maples was partially alleviated by frequent irrigation. In the second experiment, red and sugar maples were transplanted to field soil after one (1-yr) or two (2-yr) years of P+P production. Irrigation frequency requirement decreased as the trees grew and depended on environmental conditions, size at planting, source of water (rainfall versus irrigation) and species. Height and trunk diameter of 1-yr red maple was equal to that of 2-yr trees after only one year. Height and trunk diameter differences between 1-yr and 2-yr sugar maple trees persisted three years after transplanting. In the third experiment water use of 1-yr and 2-yr red and sugar maple while in P+P production was investigated. Four models of daily water-use were developed. A simple model that is suitable for growers includes species, trunk cross-sectional area (BA) and air temperature (TA) observations. An environmental model was developed using the Penman-van Bavel estimate of evapotranspiration (ET). ET required modifications based on tree characteristics, air temperature, windspeed and relative humidity to be an effective predictor of water-use. A complex model was based on a sine-cosine function of day-of-the-year. This model fits water-use data well for each species and production cycle and includes BA, ET and TA. An alternate simpler model requires only day-of-the-year, TA and BA, offering growers a relatively simple and accurate model of water use.