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Yong Ha Rhie and Jongyun Kim

peatmoss ( Konduru et al., 1999 ; Noguera et al., 2003 ). The physical properties of coir dust can differ on the basis of the country from which the material is sourced (e.g., Asia, tropical America, and Africa), and the total water-holding capacity

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Carl E. Niedziela Jr. and Paul V. Nelson

A new tube method for determining physical properties in container substrates was compared to an existing system. While both offer the advantages of undisturbed substrate and measurement of properties without altering the geometry of the substrate in the container, the tube method is easier to conduct. Both methods proved equally effective for determining air-tilled porosity, container capacity, total porosity, bulk density, and particle density.

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Manuel Abad, Fernando Fornes, Carolina Carrión, Vicente Noguera, Patricia Noguera, Ángel Maquieira and Rosa Puchades

Selected physical properties of 13 coconut coir dusts from Asia, America, and Africa were compared to physical properties of sphagnum peat. All properties studied differed significantly between and within sources, and from the peat. Coir dusts from India, Sri Lanka, and Thailand were composed mainly of pithy tissue, whereas most of those from Costa Rica, Ivory Coast, and Mexico contained abundant fiber which was reflected by a higher coarseness index (percentage by weight of particles larger than 1 mm in diameter). Coir dust was evaluated as a lightweight material, and its total porosity was above 94% (by volume). It also exhibited a high air content (from 24% to 89% by volume) but a low easily available and total water-holding capacity which ranged from <1% to 36% by volume and from 137 to 786 mL·L–1, respectively. Physical properties of coir dust were strongly dependent on particle size distribution. Both easily available and total water-holding capacity declined proportionally with increasing coarseness index, while air content was positively correlated. Relative hydraulic conductivity in the range of 0 to 10 kPa suction dropped as particle size increased. Coir dusts with a particle size distribution similar to peat showed comparatively higher aeration and lower capacity to hold total and easily available water. An air–water balance similar to that in peat became apparent in coir dust at a comparatively lower coarseness index (29% vs. 63% by weight in peat). Stepwise multiple regression analysis showed that particles with diameters in the range of 0.125 to 1 mm had a remarkable and highly significant impact on the physical properties studied, while particles <0.125 mm and >1 mm had only a slight or nonsignificant effect.

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Brian E. Jackson, Robert D. Wright and Michael C. Barnes

not considered to be a PTS because it does not contain an appreciable percentage of wood. It has been shown that pine wood chips that are hammermilled into a PTS with a particle size range and physical properties comparable to aged PB and peat

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Michael R. Evans

substrate physical properties include TPS, AFP, WHC, and bulk density. Air-filled pore space is particularly important because air-filled pores allow for gas exchange between the root environment and the outside atmosphere ( Bunt, 1988 ). Various materials

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Michael R. Evans, Matt Taylor and Jeff Kuehny

grown in plastic containers. Evans and Karcher (2004) evaluated the physical properties of peat, feather fiber, and plastic containers. They reported that plants in the peat and feather fiber biocontainers required more frequent irrigations as well as

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Johann S. Buck, Michael R. Evans and Paolo Sambo

Horticultural root substrates are designed to provide the optimal physical properties for plant growth. These properties include bulk density (g·cm-3), air-filled pore space (% v/v), total pore space (% v/v), water-filled pore space (% v/v), water-holding capacity (% v/v and w/w), and wettability. Whole, fresh parboiled rice hulls were ground to produce four grades with varying particle size distributions. Particle sizes for the four grades ranged from <0.25 to >2.80 mm. Additionally, discrete particle sizes of <0.25, 0.50, 1.00, 2.00, 2.80, and >2.80 mm were produced. For all grade distributions and particle point sizes, physical properties were determined and contrasted against Canadian sphagnum peat. As the proportion of smaller particle sizes in the distributions increased or as the particle point sizes decreased, total pore space (% v/v) and air-filled pore space (% v/v) decreased, while, bulk density (g·cm-3) and water-holding capacity (% v/v and w/w) increased. Additionally, as the proportion of particle sizes from <0.25–0.50 mm increased, the wettabilty of the whole fresh parboiled rice hull material decreased. Particle sizes ranging from 1.00–2.80 mm possessed the physical properties most suitable for plant growth in containerized greenhouse crop production and were most similar to peat.

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Sreenivas Konduru and Michael R. Evans

Chemical properties of unprocessed coconut husks varied significantly between 11 sources tested. The pH was significantly different between sources and ranged from 5.9 to 6.9. The electrical conductivities were significantly different between sources and ranged from 1.2 to 2.8 mS·cm–1. The levels of Na, K, P, and Cl were significantly different between sources and ranged from 23 to 88, 126 to 236, 8 to 33, and 304 to 704 ppm, respectively. The B, Cu, Fe, Ni, S, Zn, Mn, and Mo levels were all significantly different between sources and ranged from nondetectable levels to 12.7 ppm. The NH4-N, NO3-N, Ca, and Mg levels were not significantly different between sources and ranged from 0.2 to 1.8, 0.2 to 0.9, 2.9 to 7.3, and nondetectable to 4.6 ppm, respectively. Coir dust produced by screening of waste grade coir through 13-, 6-, or 3-mm screens had significantly different bulk densities, air-filled pore space, water filled pore space and water-holding capacities compared to nonscreened waste grade coir. However, total pore space and total solids were not significantly affected by screening. Screen size did not significantly affect physical properties. Compression pressures used for formation of coir dust blocks significantly affected physical properties. Additionally, coir dust age significantly affected chemical properties.

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N.K. Lownds, M. Banaras and P.W. Bosland

Physical characteristics [initial water content, surface area, surface area: volume (SA: V) ratio, cuticle weight, epicuticular wax content, and surface morphology] were examined to determine relationships between physical properties and water-loss `rate in pepper fruits. `Keystone', `NuMex R Naky', and `Santa Fe Grande' peppers, differing in physical characteristics, were stored at 8, 14, or 20C. Water-loss rate increased linearly with storage time at each temperature and was different for each cultivar. Water-loss rate was positively correlated with initial water content at 14 and 20C, SA: V ratio at all temperatures, and cuticle thickness at 14 and 20C. Water-loss rate was negatively correlated with surface area and epicuticular wax content at all temperatures. Stomata were absent on the fruit surface, and epicuticular wax was amorphous for each cultivar.

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Sreenivas Konduru, Michael R. Evans and Robert H. Stamps

Chemical properties of unprocessed coconut (Cocos nucifera L.) husks varied significantly among 11 sources tested. The pH and electrical conductivities were significantly different among husk sources and ranged from 5.9 to 6.9 and 1.2 to 2.8 mS·cm-1, respectively. The \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document}, \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}, Ca, and Mg levels did not differ significantly among husk sources and ranged from 0.2 to 1.8, 0.2 to 0.9, 2.9 to 7.3, and nondetectable to 4.6 mg·kg-1, respectively. Levels of P, B, Cu, Fe, Ni, S, Zn, Mn, and Mo were all significantly different among husk sources and ranged from nondetectable levels to 33 ppm. The levels of Na, K, and Cl were significantly different among husk sources and ranged from 23 to 88, 126 to 236, and 304 to 704 ppm, respectively. Coir dust (CD) produced by screening of waste-grade coir through 3-, 6-, or 13-mm mesh screens had significantly different fiber content, bulk densities, total solids, total pore space, air-filled pore space, water-filled pore space, and water-holding capacities as compared with nonscreened waste-grade coir. However, screen size did not significantly affect the physical properties of CD. Neither compression pressure nor moisture level during compression of CD blocks significantly affected rehydration of compressed CD or physical properties of rehydrated CD.