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Alexander X. Niemiera and Robert D. Wright

Abstract

A 100% pine bark medium was amended with dolomitic lime at 0, 3, or 6 kg·m−3 and periodically fertilized with 210 ml of a nutrient solution containing 100 ppm N as (NH4)2S04. At the 3- and 6-kg lime treatments, medium solution NH4-N concentrations decreased rapidly while N03-N concentrations increased. At 0 kg lime, the NH4-N decrease was slower than at the 3- and 6-kg lime treatments and N03-N was not found. Similarly treated bark without plants was used to determine a N03-N accumulation rate (NAR). NAR was greatest at 6 kg of lime, except at the last 2 sampling dates, when NAR did not differ between 3 and 6 kg of lime. This lack of difference was attributed to a limiting NH4-N supply at 6 kg of lime. In a 2nd experiment, NAR of bark treated with 6 kg of lime per m3 and fertilized with 300 ppm NH4-N was 3 times greater than with bark treated with 100 ppm NH4-N, thus supporting the contention that, over time, the NH4-N supply of the 100-ppm treatment limited nitrification. These results indicate that the stimulative influence of lime on nitrification is subject to medium pH and NH4-N status that changes over time.

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Jennifer Green, Derald A. Harp, and Kevin L. Ong

Phytophthora diseases are economically important, requiring the use of chemical fungicides and, more recently, biological controls. Recent research suggests that composted bark products may lessen the impact of the disease, even in the absence of these chemicals. An experiment was conducted to compare chemical and biological fungicides to untreated pine bark compost. Impatiens wallerana plugs were transplanted from 288 trays into 1801 trays. All plants were planted into Berger BM-7, 35% composted bark mix (Berger Horticulture, Quebec, Canada). Media was prepared by premixing one of the five following fungicide treatments: 1) Control, 2) Banrot at 0.6 g/L, 3) Root Shield at 1.6 g/L, 4) Actino-Fe at 5.1 g/Ll, or 5) SoilGard at 1.6 g/L. Plants received no fertilizer. Three strains of Phytophthora were grown in 25 °C on clarified V8 media. Pathogenic inoculum was made by macerating the growth media and fungi in 100 ml H2O. Mixture was pulse-blended for 1 min, and an additional 200 mL dH2O was added. Inoculation was 5 ml per plant. Flats were kept on a misting bench, and misted twice daily for 15 min. The experiment was set up using a RBD repeated six times with three plants per rep. Plants were rated weekly for 5 weeks using a damage scale of 0 to 5, with 0 indicating no sign of disease and 5 being dead. Statistical analysis was conducted using a Chi-Square. Disease incidence between the biological, chemical, and composted bark treatments did not differ, with all treatments providing complete control. At least in this study, the use of composted pine bark media provided Phytophthora control equivalent to current chemical and biological fungicides.

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Anne-Marie Hanson, J. Roger Harris, Robert Wright, Alex Niemiera, and Naraine Persaud

Newly transplanted container-grown landscape plants are reported to require very frequent irrigation. However, container nurseries in the U.S. commonly use growing substrates that are mostly bark, even though the contribution of bark-based growing substrates to water relations of transplanted root balls is unknown. Therefore, a field experiment was undertaken to determine water relations of a pine-bark substrate (container removed) within a drying mineral soil over a three week period. A range of common production container sizes—3.7 L (#1), 7.5 L (#2), 21.9 L (#7), 50.6 L (#15), and 104.5 L (#25)—was used. The fraction of substrate volume that is water [total volumetric water (TVW)] within the top and middle zones of substrate was compared to TVW at corresponding depths of adjacent mineral soil. The fraction of substrate and soil volume that is plant-available water [plant-available volumetric water (PAVW)] was calculated by subtracting the fraction of substrate or soil volume below where water is unavailable to most plants (measured with pressure plates) [plant-unavailable volumetric water (PUVW)] from each TVW measurement. The pine-bark substrate had a PUVW of 0.32 compared to a PUVW of 0.06 for soil. Top sections of substrate dried to near zero PAVW 6 days after irrigation for all containers. Larger container sizes maintained higher PAVW in middle sections than smaller container sizes, and PAVW was always higher in the adjacent soil than in the embedded substrate. Overall, very little PAVW is held by the embedded pine-bark growing substrate, suggesting the need for container substrates with greater water retention once transplanted to mineral soils.

Open access

H. A. Mills and F. A. Pokorny

Abstract

Nitrapyrin at 50 ppm, increased dry weights of tomato (Lycopersicon esculentum Mill.) and total N when pine bark comprised part of the medium and NH4 was part of the N treatment. If the medium consisted only of pine bark, nitrapyrin increased dry weights and total plant N with NO3–N and/or NH4–N treatments. The NO3–N level in the medium was higher with all N treatments when nitrapyrin was incorporated. The increase in plant growth is directly related to the higher NO3–N levels in each medium where nitrapyrin was incorporated. The higher media NO3–N with nitrapyrin are attributed to inhibition of the nitrification process and a subsequent inhibitory effect on NO3–N loss.

Free access

A.M. Shirazi and G.H. Ware

The genus Ulmus contains numerous stress-tolerant species, especially those from areas of China with climates similar to various regions of the United States. Lace-bark elm, Ulmus parvifolia, the true Chinese elm, has an extensive temperature distribution range in China and offers great promise as a street tree. The high resistance of this elm to Dutch elm disease and other elm problems makes it an excellent tree for urban landscapes. Two new U. parvifolia cultivars, Athena® and Allee®, are not cold hardy for northern climates and there is a need for new cold hardy lace-bark elms. Screening thousands of seedlings for cold hardiness, upright form, beautiful bark characteristics, and larger leaves will bring the most desirable U. parvifolia cultivars into the green industry. We determined that seed dormancy and the percentage of seed germination of four selected lacebark elms after 2 and 4 weeks were >30% and >50%, respectively. There were significant differences in stem cold hardiness among new lace-bark elms from China (about –32 to –40 °C). Laboratory determination of cold hardiness can provide great advantages over years of field testing. Response to the outdoor temperature in December, January, and February on a seed cold hardiness freezing test showed significant reduction in seed germination, especially at –30 °C. Freezing test of seeds to –40 °C, resulted in lt 50 of –3 to –5 °C in December, so, it is less likely that these U. parvifoilia will become invasive in northern latitudes. Invasiveness of these U. parvifolia for higher zones, e.g., 6–8 could be greater and selection of these elms is suitable for zones 5 and lower. Planting these elms in zones 4, 3, and 2 will give us useful information regarding their winter performance.

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T.E. Bilderback

Ilex × `Nellie R. Stevens' holly, Rhododendron sp. `Hinodegeri' azalea and Pyracantha coccinea, scarlet firethorn rooted cuttings were potted in • 3.81 containers. Irrigation was applied by Dram rings daily, or every 2,4,or 6 days. Approximately 1000 ml of water were applied at each irrigation. Three container media, including pine bark, and pine bark amended with either Terra-Sorb AG synthetic moisture extender incorporated at 1.2 kg/m3 or Aqua-Gro G wetting agent incorporated at 0.9 kg/m3 plus monthly drenches of 700 ml of 2500 ppm Aqua-Gro L were compared for physical and chemical properties and plant growth responses. Decreasing irrigation decreased pH, increased nutrient leachate levels, and increased foliar tissue levels of N,P,K,Ca,and Fe in holly and azalea. Pyracantha top and root dry weight was reduced at 4 and 6 day irrigation intervals, holly top growth was reduced by 6 day and azalea had greatest shoot growth at 2 day irrigation and was reduced by other irrigation frequencies. Top growth of all 3 species and root growth of pyracantha was reduced in the pine bark treatment.

Free access

William E. Klingeman*, Darren K. Robinson, and Gary L. McDaniel

Mugwort, or false chrysanthemum (Artemisia vulgaris L) is a well-adapted invasive plant that presents increasing management challenges to agricultural producers, Green Industry professionals and homeowners across portions of the eastern U.S. The ability of mugwort to regenerate from cut rhizome sections has not been adequately quantified for substrates that are typical of landscapes and nursery fields, container nurseries, and propagation beds. Cut rhizome sections were analyzed by rhizome color, length, and the presence or absence of a leaf scale. Media substrates included pine bark, sand, and soil. Rhizomes darken with time and color did not account for differences in growth among treatments. When grown in pine bark, sand, and soil substrates during 45-d trials, 85%, 78%, and 69% of 2 cm-long rhizome sections produced both roots and shoots. These results contrast with previous research. When rhizome fragments 0.5 cm long did not include a leaf scale, slightly fewer than 31% produced both roots and shoots in soil. Fewer rhizomes survived in soil, but root and shoot fresh masses of soil-grown rhizomes were greater than rhizomes that were regenerated in pine bark and sand. When rhizome sections had a leaf scale, survival, fresh masses of roots and shoots, shoot height, leaf number and root lengths were greater, regardless of substrate type. Root initials emerged in the internode between leaf scales and also adjacent to leaf scales. Shoot emergence preceded root emergence from rhizome sections. Growers, landscape managers and homeowners should scout regularly and initiate aggressive controls when mugwort populations are found.

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Jeff L. Sibley, John M. Ruter, and D. Joseph Eakes

The objective of this study was to determine differences in the bulk anthocyanin content of bark tissue of container-grown red maple (Acer rubrum L. and Acer ×freemanii E. Murray) at two Georgia locations with different environmental conditions. Rooted cuttings and tissue-cultured plantlets of eight cultivars were grown in either Blairsville or Tifton, Ga. [U.S. Dept. of Agriculture (USDA) Hardiness Zones 6b and 8a; American Horticultural Society (AHS) Heat Zones 5 and 8, respectively], from June 1995 until Dec. 1996. Bark tissue from twigs of trees grown in Blairsville was visually redder and contained more total anthocyanin than did that of trees grown in Tifton. Levels of total anthocyanins were higher (P = 0.0007) at Blairsville (0.087 mg·g-1, N = 48) than at Tifton (0.068 mg·g-1, N = 47). At both locations the levels were highest in `Landsburg' (`Firedance'™), followed by `Franksred' (`Red Sunset'™) and `October Glory'. This is the first report to quantify anthocyanin differences in bark tissue of container-grown trees. Cooler nights in Blairsville might have contributed to increased coloration by reducing respiratory losses, thus leaving more carbohydrates available for pigment production.

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William F. Hayslett, P. R. Thangudu, and Sabrina Shaw

A field study was conducted at Tennessee State University's research station to evaluate the effect of hardwood bark mulch on the winter survival of garden mums. A randomized complete block design was used. Cultivars used were adorn, encore, grandchild, jackpot, legend, minnautumn, minnwhite and triump. At the end of the flowering season the tops were removed leaving a four inch stubble in the mulch. The number of mum plants that resumed growth the following spring were counted for each cultivar. There was a difference in the winter survival of the different cultivars as well as a significant difference in the mulch treated and the control. Grandchild and jackpot were most cold hardy followed by encore, minnwhite, minnautumn, triump, legend, and adorn. Grandchild and jackpot with four inches of hardwood bark mulch had an 88 percent survival while the control had a 44 percent survival. Adorn. had a 51 percent survival with four inches of mulch and a 20 percent survival in the control. This data shows that hardwood bark mulch holds a great potential for providing excellent winter protection for garden mums.

Free access

Carole L. Bassett, Robert E. Farrell Jr., and Timothy S. Artlip

Genes whose expression is regulated by exposure to low temperature (LT) in peach (Prunus persica L. Batsch.) bark were identified by PCR suppression subtractive hybridization. Among the genes identified by this technique were several that had previously been associated with LT responsiveness, as well as a few that have not been reported to be regulated by cold. Genes represented by the first group included Ppdhn1, previously characterized as a seasonally expressed gene predominantly seen in bark tissue collected in winter months. A novel dehydrin found in this study, Ppdhn3, was also observed to be up-regulated at LT and seasonally expressed. Two genes not previously associated with LT response were found to be up-regulated at 5 °C. These genes encode a polypeptide related to some unknown mitochondrial process (Pptar1p) or a transducin-like protein (Pptlp1) that may be associated with signal transduction. Expression of these genes with respect to seasonal variation and drought stress is compared to genes from peach bark (Ppdhn1 and Ppdhn2), whose patterns of expression in different seasons and under water deficit are well documented.