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Juha Heiskanen

Two commercially produced growth media made of light, low humified sphagnum peat, were used to determine how filling into containers affects the particle size distribution and water retention characteristics of peat. It was shown that the filling procedure used broke up the peat particles, resulting in a significant increase in the proportion of particles < 1 mm (g·g-1). Due to the increased proportion of fine particles, the water retention of the peat media increased under wet conditions (-0.1 kPa matric potential), while the air-filled porosity decreased to nearly 0. Also, at matric potentials lower than -0.1 kPa, the reduction in air-filled porosity may restrict aeration and availability of oxygen to roots, thus reducing growth of plants.

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M.A. Kasrawi, N. Khraishi, and Y. Tabaza

A greenhouse experiment was conducted over two growing seasons to study the physical and mechanical properties of a recycled multilayer plastic cover and its effect on the production of greenhouse-grown tomatoes. Two experimental greenhouses were constructed, one covered with recycled multilayer film and the other with conventional virgin monolayer film. The air temperature under both covers was similar; the soil temperature in the recycled multilayer house was a few degrees lower in the afternoon hours to midnight than in the virgin monolayer house. The recycled multilayer film retained its strength and elasticity over a useful service life of 7 months (one growing season), after which severe degradation occurred as manifested by a 50% loss of elongation at break. During the useful lifetime of the film, haziness, light scattering, and light transmission of the recycled film was similar to the conventional film. The thermal analysis of the recycled film revealed a low stability against thermo-oxidative degradation and the infrared analysis indicated the presence of a measurable amount of degradation products, mainly carbonyl groups, in the recycled film in comparison with conventional film. During the useful lifetime of recycled film, yield components of the tomato crop were identical to the conventional film in both growing seasons. In conclusion, waste plastic recycling offers an attractive solution to nuisance environmental problems. However, the useful lifetime of recycled films needs to be improved.

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Jiwon Jeong, Jeffrey K. Brecht, Donald J. Huber, and Steven A. Sargent

A study was conducted to determine the effect of 1-methylcyclopropene (1-MCP) on textural changes in fresh-cut tomato (Lycopersicon esculentum, Mill.) slices during storage at 5 °C. The relationship between fruit developmental stage and tissue watersoaking development was also determined. Fresh-cut tomato slices prepared from light-red fruit that had been exposed to 1-MCP (1 μL·L-1 for 24 h at 5 °C) retained significantly higher pericarp firmness during storage at 5 °C for 10 d than slices from nontreated fruit or slices stored at 10 or 15 °C and they also had a significantly higher ethylene production maximum. 1-MCP (1 or 10 μL·L-1 for 24 h at 5 °C) had no affect on the firmness of fresh-cut, red tomato slices at 5 °C or on slices prepared from 5 °C-stored, intact red tomatoes. Nor did 1-MCP treatment have a significant effect on electrolyte leakage of tomato slices or intact fruit stored at 5 °C. Slices from fruit of the same developmental stage but with higher initial firmness values had less watersoaking development and responded better to 1-MCP treatment during 8 d storage at 5 °C. 1-MCP (1 μL·L-1) was more effective in reducing watersoaking in light red stage tomato slices when applied at 5 °C for 24 h compared with 1-MCP applied at 10 or 15 °C. Watersoaking development was also more rapid in fresh-cut tomato slices as initial fruit ripeness advanced from breaker to red stage. Our results suggest that watersoaking development in fresh-cut tomato slices is an ethylene-mediated symptom of senescence and not a symptom of chilling injury as had previously been proposed.

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Magdalena Zazirska Gabriel, James E. Altland, and James S. Owen Jr

and inorganic components commonly used by nursery growers in California. The aforementioned papers illustrate the broad number of substrate components and virtually unlimited number of combinations that nursery growers use. Physical properties of

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James E. Altland and Charles Krause

-Kristensen (2005) assessed the suitability of miscanthus clippings for use as a container substrate by measuring various physical properties of this material and other composted crop residues. Their ( Dresboll and Thorup-Kristensen, 2005 ) research did not include

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Carlo Mininni, Pietro Santamaria, Hamada M. Abdelrahman, Claudio Cocozza, Teodoro Miano, Francesco Montesano, and Angelo Parente

The most common substrate used in horticulture for growing seedlings and soilless plants cultivation is peat, alone or in mixture ( Chavez et al., 2008 ), because of its good chemical and physical properties. Unfortunately, peat is a very expensive

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James E. Altland, James S. Owen Jr., Brian E. Jackson, and Jeb S. Fields

1970s, with increasing acceptance due to its availability, favorable physical properties, and lack of detrimental chemical constituents when used to grow container crops. The harvesting, dilution or contamination with wood from other species, lumber

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Jeb S. Fields, William C. Fonteno, Brian E. Jackson, Joshua L. Heitman, and James S. Owen Jr.

to determine basic physical properties [total porosity (TP), AS, and CC] of a substrate for a specific size and shaped container ( Bilderback and Fonteno, 1987 ; Milks et al., 1989b ). Container size has been proven to significantly alter substrate

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George Gizas and Dimitrios Savvas

water availability in the rhizosphere strongly depend on the physical properties of the substrates, which in turn are conditioned by the shape and size of their constituent particles ( Da Silva et al., 1993 ; Hanan et al., 1981 ; Raviv et al., 2002

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James E. Altland and Charles Krause

with sodium vapor lights from 0600 to 2000 hr . A sample of each substrate was set aside at the time of potting to determine physical properties. Substrates were packed in Al cores (3 inches tall by 3 inches i.d.) according to methods described by