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commercially in the U.S. industry to influence substrate physical properties, N immobilization, and fertigation practices (i.e., combined fertilization and irrigation). Comparing major sources of wood fiber vs. more traditional substrate materials, such as

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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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Root substrates (substrates) are formulated from various inorganic and organic components to provide suitable physical and chemical properties as required by the specific crop and growing conditions ( Bunt, 1988 ; Nelson, 2003 ). Important

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, 1991 ). Soil physical and chemical properties. Significant differences between organic and conventional soils were not found in the physical and chemical properties of the preplant soil ( Table 2 ). In early April, organic soils had a significantly

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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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would improve physical and chemical properties of alleyway soil compared with bare, repeatedly cultivated soil. Materials and Methods Experimental design. A field experiment was conducted in an established, 3-year-old commercial ‘Meeker’ red raspberry

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Abstract

Cuttings of three ornamental species [Ilex × ‘Nellie R. Stevens’, (I. aquifolium × I. cornuta) Van Lennep, × Cupressocyparis leylandii Jacks & Dall. ‘Haggerston Grey’, and Lagerstroemia indica L.] were inserted in 11 media to determine the effects of physical properties of propagation media on rooting response. The physical properties of seven propagation media were altered by manipulating particle size distribution of a 1 aged pine bark : 1 composted hardwood bark (v/v) medium. Four other propagation media were used for comparison. Container capacity air space ranged from 12% to 40%, and water held after drainage in the root zone ranged from 35% to 55%. Variation in rooting response of cuttings occurred, but differences could not be attributed to the physical properties of the various media. In addition, no relationship between rooting response and engineered combinations of hardwood bark and pine bark were detected.

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Popular press articles report that consumers often experience inconsistent results with retail potting media; however, few reports in the popular or scientific literature have quantified the variability in media properties. The purpose of this study was to assess the variability in physical and chemical properties among different brands of retail potting media and within certain brands. Twenty-four different packages of branded media, and multiple packages of five brands, were acquired from nine regional and national retail chain stores located in the Salt Lake City, Utah, area. Samples were analyzed for five physical and nine chemical properties. The coefficients of variation (cvs) among brands for initial gravimetric water content, bulk density, porosity, water retention, and air space were 85%, 74%, 21%, 59%, and 44%, respectively. The cvs among brands for saturated media (SM) pH, SM extract electrical conductivity (EC), nitrate-nitrogen (NO3-N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), total carbon (C), total nitrogen (N), and C:N ratio were 18%, 81%, 132%, 153%, 96%, 78%, 71%, 36%, 45%, and 49%, respectively. Only one of the 24 brands met all published standards for chemical properties of premium media. Thirteen of the brands did not meet standards for NO3-N; 12 did not meet standards for pH; and six did not meet standards for EC. There was more variation in physical and chemical properties among brands than within a brand of media. Label information describing media composition was not consistent with certain physical and chemical properties. No recommendations can be made which would allow consumers to select media that meets published standards. These results indicate better awareness of and/or adherence to standards is needed by the retail media industry to improve product quality and consistency.

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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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Abstract

Selected physical and chemical properties of pine bark, 2 sources of coal cinders, and mixtures thereof, were evaluated as container media components. Bulk density, air-filled pore space, particle-size distribution, cation exchange capacity, and soluble salt levels were quantified. Aged and freshly combusted cinders demonstrated no major physical or chemical disadvantages when used in container media. Acid and water extracts indicated that both sources of coal cinders released significant amounts of micronutrients and heavy metals. The concentrations of certain metals were sufficiently high to warrant concern over the possibility of plant nutritional disorders; whereas, other released elements resembled those of a supplemental micronutrient fertilizer.

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