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R.A. Mirabello, A.E. Einert, and G.L. Klingaman

The use of shredded bark, wood chips, and other organic mulches to conserve water and moderate soil temperatures is a common practice in landscape maintenance. Four mulch materials (cottonseed hulls, cypress pulp, pine bark, and pine straw) were examined to determine effects on plant growth and soil conditions in annual flower beds during a 1-year rotation of warm season to cool season annuals. Inhibited plant growth was observed in pine bark treatments at the conclusion of the growing season for both plantings. Effects on soil conditions were insignificant over the year-long study in pine bark treatments. To further investigate potential phytotoxic effects of pine bark and other mulch used in the initial study, a seed bioassay was performed to determine the influence of mulch extracts in solution on germination and primary root elongation.

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M.P. Bañados, M.S. Santiago, and C. Eterovic

The main form of nitrogen reserves during overwintering are amino acids and proteins. Specific proteins called bark storage proteins (BSP) have been characterized in many tree species. To identify BSPs in `O'Henry' peach, `Angeleno' plum, and `Early Burlat' cherry trees, samples of bark were collected from January through December 1993 from trees growing under field conditions in Santiago, Chile. SDS-PAGE analyses were used to characterize the seasonal variation on the protein pattern on the bark of those Prunus species. A 60 kDa BSP was identified in the bark of all three species, which corresponds to the main protein present in the bark during the winter. This protein may play an important role as a nitrogen reserve in these fruit trees.

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Zoran Jeknic and Tony H. H. Chen

The development of bud dormancy in poplar plants is initiated by short-day photoperiods (SD). During the development of bud dormancy, there was a gradual increase in the force required to peel off the bark from the stems. We measured the force required for bark peeling and investigated the cellular changes associated with this phenomenon. Stem samples were collected from plants which had been grown under SD for different period of time up to 10 weeks. At each sampling date, the forces required to peel off the bark were measured by a tensiometer. At the same time, samples were fixed to examine ultrastructural changes by transmission electron microscopy. We have observed that there was a significant increase in the force (in Newtons) required to peel off bark from poplar stems when the development of dormancy was initiated by SD treatment. Many ultrastructural changes were observed, including the accumulation of bark storage proteins, the break down of the central vacuole to form many small vacuoles, thickened cell walls, etc. Efforts have been made to relate ultrastructural alterations to changes in the force required for bark peeling.

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Graham J. Wright and Irwin E. Smith

Composted pine bark is one of the most important substrates used in the seedling industry today. Previous work suggested the availability of inherent Potassium (K) in the bark. This research confirmed the availability of K and indicated that little or no K is needed for seedling production when pine bark is used as a substrate. Pre-enrichment rates ranged from 0 to 460 g.K.m-3, with a supplemental solution application of 0 to 200 mg.K.l-1. No evidence of K deficiencies or toxicities were detected. Three K sources, KCl, KNO3, and K2SO4 were used in the pre-enrichment of the bark. No differences were noted for top fresh mass, seedling height, root dry mass, root to shoot ratio and percentage moisture. Seedlings grown in treatments without and supplementary K showed tissue contents of 162.5 This research suggests the possibility of reducing the levels of-K applied to seedlings grown in a composted pine bark substrate.

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Alexander X. Niemiera

Amending soilless media with micronutrients is a routine nursery practice. The objective of this research was to determine the micronutrient status of pine bark amended with two sulfate micronutrient sources and a control (unmended). Limed pine bark was unamended, amended with Ironite (1 and 2 g/l), or Micromax (1g/l). Bark was irrigated with distilled water in amounts equivalent to 30, 60, 90, and 120 irrigations (.63 cm per irrigation). Following irrigations, Cu, Fe, Mn, and Zn were extracted with a modified saturated media extract method using .001M DPTA as the extractant. Irrigation amount had no effect on Cu and Mn concentrations which were greater in the Micromax treatment than the Ironite or control treatments. A micronutrient source × irrigation interaction existed for Fe and Zn concentrations requiring regression analysis. In general, slope values indicating the decrease in micronutrient values with increasing irrigations were quite low (≤ .001) for each source. Regardless of irrigation amount, Fe and Zn concentrations were similar for amended and unamended bark.

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Jeffrey G. Williamson and E. Paul Miller

Bearing `Misty' and `Star' southern highbush blueberries were grown on pine bark beds and fertilized at three rates using granular and liquid fertilizers with a 3–1–2 (1N–0.83K–0.88P) ratio. Granular fertilizer was applied 8 times per year at 4-week intervals beginning in April and continuing through October. Liquid fertilizer was applied with low volume irrigation 16 times per year at 2-week intervals during the same period. During the growing season, irrigation was applied at 2- to 3-day intervals in the absence of rain. A 2 cultivar × 2 fertilizer type × 3 fertilizer rate factorial arrangement of treatments was replicated 8 times in a randomized complete-block design. All fruits were harvested from single-plant plots at 3- to 4-day intervals. Canopy volume was not affected by fertilizer type, but fruit yield was slightly greater for granular than for liquid fertilizer treatments. In 2003, fruit yield of 2.5-year-old `Misty' and `Star' plants increased with increasing fertilizer rates up to the highest rate tested (50 g N/plant/year). Similarly, in 2004, fruit yields increased with increasing fertilizer rates up to the highest rate (81 g N/plant/year). Root distribution was limited to the 12-cm-deep layer of pine bark with very few roots penetrating into the underlying soil. The positive growth responses of blueberry plants to high fertilizer rates in pine bark beds suggests that soluble fertilizer was leached through the pine bark layer into the soil below the root zone. More frequent, lighter applications of soluble fertilizers, use of slow-release or controlled-release fertilizers, and careful irrigation management may improve fertilizer use efficiency of blueberry plantings on pine bark beds.

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Hannah M. Mathers and Michele M. Bigger

Many nurseries within Ohio and northeastern, southeastern, and western United States, and Canada have reported severe bark splitting and scald-type problems in 2005. The amount and severity of damage seen in 2005 has been unlike anything seen before. At Ohio State University, samples from across the state started appearing in 2003–04 and increased in incidence in 2005. Growers' reports of exceeding losses of 5% of their inventory or 3000 to 4000 trees per nursery are not uncommon. At an average cost of $125 per tree and with the number of nurseries reporting problems, the stock losses in Ohio have been staggering, in excess of several million dollars. The trees that we have seen problems on in 2005 have been callery pears, yoshino cherry, kwanzan cherry, crab apples, sycamore, serviceberry, hawthorn, mountain ash, black gum, paper bark maple, japanese maples, norway maple `Emerald Queen', red maples, kousa dogwood, magnolia `Elizabeth' and the yellow magnolias such as `Butterflies', `Sawada's Cream', `Yellow Bird', and `Yellow Lantern'. It has long been observed that the actual cause of a bark crack was “preset” by a wound such as the improper removal of a basal sprout, herbicide, leaving of a branch stub, or lack of cold hardiness. Cold and frost may be contributing to the increase in bark splitting across the United States; however, new research results at Ohio State University regarding the effects of DNA preemergent herbicides in the reduction of root hardiness and regrowth potential, sprout removal and other mechanical injuries, and postemergent herbicide application will reveal these are more the causal agents.

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John M. Englert, Gary D. Coleman, Tony H.H. Chen, and Leslie H. Fuchigami

A 32kDa bark storage protein (BSP) which accumulates in the fall and is degraded in the spring has been identified in Populus deltoides bark. The BSP gene has been shown to be regulated by short day (SD) photoperiod (8 h). The physiological condition of the plant and the environmental factors necessary for the degradation and retranslocation of BSP are of considerable interest for determining the role of this protein in the remobilization of nitrogen in trees.

Poplar plants were placed in a SD growth chamber for 4 or 7 weeks to induce growth cessation (bud set) or dormancy, respectively. BSP accumulated to high levels in bark tissues after 3 weeks SD and remained high through 7 weeks SD. Plants in which growth had stopped (4 weeks SD), or in which dormancy (7 weeks SD) was broken with hydrogen cyanamide (0.5 M) or chilling (4 weeks 0C) broke bud within 1 week of being placed into long day (LD) conditions. Dormant plants which were not chilled broke bud after 3 weeks LD. BSP levels decreased around the time of budbreak, suggesting that the degradation of BSP is dependent on the need for a nitrogen sink, ie. budbreak and new shoot growth.

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Thomas Yeager, Ed Gilman, Diane Weigle, and Claudia Larsen

Columns (4 × 15 cm) of a pine bark medium amended with the equivalent of 4.2 kg per cubic meter of dolomitic limestone and either 0, 2.4, 4.7, 7.1 or 9.5 mg of urea-formaldehyde (38% N) per cubic centimeter of medium were leached daily with 16 ml of deionized water (pH 5.5). Leachate total N, NO3 --N and NH4 +-N concentrations were determined on day 1, 3, 5, 7, 14, 28, 49, 91, 133, 203, 273 and 343. Leachate total N ranged from 600 ppm on day 1 for the 9.5 mg treatment to 4 ppm on day 273 for the 2.4 mg treatment. Leachate NH4 +-N concentrations ranged from 38 ppm c4 day 3 for the 9.5 mg treatment to less than 1 ppm on day 7 for the 2.4 mg treatment and were less than total N concentrations at each sampling time. Leachate NO3 --N was not detectable during the experimental period. Eleven, 16, 20 and 25% of the applied N leached from the columns amended with 2.4, 4.7, 7.1 or 9.5 mg of urea-formaldehyde per cubic centimeter of pine bark, respectively, during the 371 day experiment.

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John D. Lea-Cox and Irwin E. Smith

Pine bark is utilized as a substrate in citrus nurseries in South Africa. The Nitrogen (N) content of pine bark is inherently low, and due to the volubility of N, must be supplied on a continual basis to ensure optimum growth rates of young citrus nursery stock. Three citrus rootstock (rough lemon, carrizo citrange and cleopatra mandarin) showed no difference in stem diameter or total dry mass (TDM) when supplied N at concentrations between 25 and 200 mg ·l-1 N in the nutrient solution over a 12 month growing period. Free leaf arginine increased when N was supplied at 400 mg·l-1 N. The form of N affected the growth of rough lemon. High NH4-N:NO3-N (75:25) ratios decreased TDM when Sulfur (S) was absent from the nutrient solution, but not if S was present. Free arginine increased in leaves at high NH4-N (No S) ratios, but not at high NH4-N (S supplied) ratios. Free leaf arginine was correlated with free leaf ammonia. These results have important implications for reducing the concentration of N in nutrient solutions used in citrus nurseries and may indicate that higher NH4-N ratios can be used when adequate S is also supplied.