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. Discrepancies in the results could be attributed to the exclusion of some of the connected interparticle pores due to air entrapment and the hydrophobic tendencies of some organic components such as peat or pine bark ( Bunt, 1984 ; Fields et al., 2014

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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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species. Evans and Gachukia (2007) also reported how PBH affected the physical properties of sphagnum peat-based substrates compared with perlite. However, the effects that PBH has on the chemical properties of sphagnum peat-based substrates compared

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An automatic irrigation system was designed for use on green-house tomatoes growing in peat-based substrates. This system uses electronic tensiometers to monitor continuously substrate matric potential (SMP) in peat-bags. The system also uses the Penman equation to evaluate potential evapotranspiration (PET) through the acquisition of many greenhouse environmental parameters. Through a series of linear equations, estimates of PET are used in a computer-controller system to vary the electrical conductivity (EC) of irrigated nutrient solutions, as well as SMP setpoints at which irrigations are started. Such modifications to current irrigation management systems may improve fruit quality and reduce the risk of water stress during periods of high PET by irrigating more frequently with less-concentrated nutrient solutions. Conversely, during periods of low PET, irrigation is less frequent with more-concentrated nutrient solutions. Although no differences were found in fruit number or overall yield using variable nutrient solution EC, plant fresh weight was higher in those treatments. It is concluded that an integrated tensiometer-PET system may give increased precision to irrigation management and the control of crop growth in the greenhouse.

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Abstract

Peat-sand (1:1, by volume) and wood-sand (2:1, by volume) mixes in 10 cm plastic pots were planted with Epipremnum aureum Linden & Andre cv. Tricolor (pothos), Coleus glumei Benth (coleus), and Brassaia actinophylla Endl. (schefflera). After the pH of the leachate had dropped to between 4.0 and 5.0, pots received a single irrigation with solutions NaHCO3 and KHCO3. For the peat mix, the highest concentrations (0.20 M) of NaHCO3 and KHCO3 raised the leachate pH to nearly 9.0; the pH subsequently dropped most rapidly in pots containing coleus and schefflera, and slowest with pothos. In pots containing the wood-sand mix, the pH climbed as high as 8.0 immediately after treatment with 0.08 m KHCO3, then decreased slowly in pothos and more rapidly with the other 2 species. In peat mixes, the final leachate pH was nearly one unit greater than the saturation paste pH of the soil. In wood-sand pots, mix from the bottom half of the pot was always lower in pH than mix from the top half. Except for schefflera the pH of the last leachate obtained was nearer the pH of the bottom half of the pot than that of the top half.

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Abstract

Chrysanthemum plants (Chrysanthemum morifolium Ramat. cv. Bright Golden Anne) were grown for 84 days in plastic pots containing media treated with inorganic fertilizers or liquid sewage sludge, added at a rate of 50, 100, or 200 ml/week, to determine if sludge could be used as a fertilizer. Plants grown with sludge at all application rates had higher N and lower K concentrations compared to plants grown with inorganic fertilizers. Leaf concentration of P, Ca, Mg, Fe, Zn, Cu, Cd, Ni, and Pb of plants grown with 50 ml sludge/week were similar to plants receiving inorganic fertilizers. As sludge application rate increased, leaf concentrations of Fe and Cu increased of plants grown in media consisting of all sand or all peat and Zn increased in leaves of plants grown in the standard greenhouse media (1 soil: 1 sand:l peat, by volume). Sludge-treated media had a higher pH and extractable Cu concentration, and a lower extractable K concentration, than media without sludge. Plants receiving 50 ml sludge/week grew as well as plants grown with inorganic fertilizers.

Open Access

In Europe and North America, there is increasing pressure to partly or totally replace peat, coir, rockwool, perlite, and polystyrene components of growing media with sustainable materials such as organic industrial byproducts of local origin

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technologies that help improve WUE ( Beeson et al., 2004 ). Water usage during crop production in fiber containers has been studied, and Evans and Karcher (2004) reported that crop production in peat-fiber containers used 2.25 times the water needed for

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potting media, which are usually comprised of a mix of substrates. For example, a Florida survey found that participating nurseries used 16 different substrate components, resulting in 26 different mixtures ( Yeager and Newton, 2001 ). Peat moss has been a

Open Access

. 2008. The plants had several unfolded leaves and were considered to be at the commercial transplant stage. The rooted cuttings were transplanted into 15-cm round pots (1780 mL) containing a commercial peat-based substrate (Metro-Mix 360; Sun Gro

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