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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.

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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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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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Alex X. Niemiera, Ted E. Bilderback, and Carol E. Leda

Pine bark (PB), either unamended or amended with sand (S) at 9 PB: 1 S or 5 PB:1 S (v/v), was fertilized with solutions of 100,200, or 300 mg N/liter solution and tested for N concentration using the pour-through method (PT). PB, 9 PB: 1 S, and 5 PB: 1 S had porosities of 84%, 75%, and 66%, respectively. PT NO3-N concentrations, obtained via PT, of the 5 PB:1 S substrate were 43%,28%, and 15% higher than PB NO3-N values for the 100,200, and 300 mg·liter-1 treatments, respectively. Differences in N concentration obtained with PT can be attributed to substrate physical characteristics. Based on the results, data for PT should be interpreted with regard to substrate porosity.

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Tyler C. Hoskins, James S. Owen Jr., and Alex X. Niemiera

solute transport is warranted to develop a more direct and thorough understanding of water and solute transport in soilless systems. Physical properties of the pine-bark and sand blends commonly used in the mid-Atlantic and southeastern U.S. nursery

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Brian E. Jackson, Robert D. Wright, and Mark M. Alley

In recent years, several peat and pine bark (PB) alternative substrates have been developed and researched in the United States and throughout the world. The interest in new substrates is in response to the increasing cost and environmental issues

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Jeff B. Million, James E. Barrett, Terril A. Nell, and David G. Clark

Dendranthema×grandiflorum (Ramat.) were grown in either a peat-based or pine bark—based medium and drenched with growth retardants at a range of concentrations to generate dose : response curves. The effect of ancymidol, paclobutrazol, and uniconazole on stem elongation was less in the pine bark—based than in the peat-based medium. Generally, the concentrations required to achieve the same response were 3- to 4-fold as high in the pine bark—based medium as in the peat-based medium. However, chlormequat was slightly more active in the pine bark—based medium than in the peat-based medium. Chemical names used: α-cyclopropyl-α—(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol); (±)-(R*,R*)-β-[(4-chlorophenyl)methyl]-α-(1,1-di methyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol); (E)-(RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)pent -l-en-3-ol (uniconazole); 2-chloroethyltrimethylammonium chloride (chlormequat).

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Amy N. Wright, Alex X. Niemiera, J. Roger Harris, and Robert D. Wright

The objective of this study was to determine the effect of micronutrient fertilization on seedling growth in pine bark with pH ranging from 4.0 to 5.5. Koelreuteria paniculata (Laxm.) was container-grown from seed in pine bark amended (preplant) with 0, 1.2, 2.4, or 3.6 kg/m3 dolomitic limestone and 0 or 0.9 kg/m3 sulfate-based micronutrient fertilizer (Micromax ®). Initial pine bark pH for each lime rate was 4.0, 4.5, 5.0, and 5.5, respectively. Final pH (week 10) ranged from 4.7 to 6.4. Ca and Mg supply in irrigation water was 10.2 and 4.2 mg·L–1. Seedlings were harvested 10 weeks after planting, and shoot dry weight and height were determined. Pine bark solution was extracted using the pour-through method at 3, 7, and 10 weeks after planting. Solution pH was measured, and solutions were analyzed for Ca, Mg, Fe, Mn, Cu, and Zn. Shoot dry weight and height were higher in micronutrient-amended bark than in bark without added micronutrients. Lime (1.2 kg·\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{m}^{-_{3}}\) \end{document}) increased growth only in the absence of micronutrient additions. In general, adding micronutrients increased pine bark solution Ca, Mg, and micronutrient concentrations. Adding lime increased pine bark solution pH and Mg concentration and either had no effect on or decreased solution Ca and micronutrient concentrations. Regardless of pine bark pH, micronutrient additions resulted in improved growth and adding lime was not necessary.

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Richard G. Snyder

Successful greenhouse tomato businesses are able to keep production and quality high while maintaining reasonable cost controls. One way of controlling costs is to use growing media that are locally available in good supply, and therefore of low cost. In Mississippi. as in other states in the southeast, pine bark is an available byproduct resource from the forestry industry; fines (<=95mm diameter) can be used as a growing medium following composting. Rice hulls are a readily available waste product from rice mills, especially in the Mississippi Delta region; these are suitable after being crushed and composted.

In comparison to plants grown in rock wool, yield from plants in pine bark fines, rice hulls, or sand were higher, while quality was not significantly different in the l-crop/year system. In a spring crop, yield and quality were higher from plants in pine bark, rice hulls, and rock wool than from those grown in sand. On a per plant basis, cost for the rock wool system, perlite system (pre-bagged), perlite (bulk), peat moss, sand, composted rice hulls, and pine bark lines are $1.50, $1.00, $0.35, $0.60, $0.24, $0.22 and $0.17, respectively. Pine bark and rice hulls are good choices for growing media for greenhouse tomatoes in areas where they are available.

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Ronald F. Walden and Alex X. Niemiera

The pour-through (PT) nutrient extraction method involves collection of leachate at the container bottom that results from displacement of substrate solution by water applied to the substrate surface. The PT is a convenient and effective means of monitoring the nutritional status of the soilless container substrates used in the nursery industry, but is less convenient for large containers, particularly those used in the “pot-in-pot” system of growing trees in production containers within in-ground socket containers. We describe a simple vacuum method of extracting solution from pine bark in containers using ceramic cup samplers. When N was applied to a pine bark substrate at 56–280 mg/L, extractable N was slightly higher for the PT than for the ceramic cup method. The correlation between applied and extractable N was 0.99 for both methods. Further comparison of pine bark extract nutrient and pH levels for PT and ceramic cup methods will be presented.