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Andrew G. Reynolds and Andrew P. Naylor

Glasshouse-grown `Pinot noir' and `Riesling' grapevines (Vitis vinifera L.) were subjected to one of four water stress durations [no water deficit (control); and water deficits imposed postbloom, lag phase, and veraison] in combination with three soil water-holding capacities (0%, 26%, and 52% gravel, by volume). Vines subjected to increasing water stress duration had less cumulative lateral shoot length and lower shoot count, leaf size, and berry weights than those not stressed. Soluble solids concentration (SSC) during maturation and pH at harvest also increased with increasing water stress duration, but titratable acidity was not affected. Transpiration and stomatal conductance also were reduced with increased water stress duration, but soil water increased, reflecting the larger leaf surface on vines with veraison-imposed deficits. Reducing water-holding capacity (by increasing the percentage of gravel in the soil) tended to increase berry weight and SSC but reduced lateral shoot growth. The 52% gravel treatments increased transpiration rate and stomatal conductance for `Riesling' but reduced them slightly in `Pinot noir'. Percentage of soil moisture was reduced linearly with reduced water-holding capacity. These results indicate that early irrigation deficits may advance fruit maturity of wine grapes with concomitant reductions in vegetative growth. Differential responses of these cultivars to soil water-holding capacity also should help to identify suitable wine grape cultivars as the wine grape industry expands into areas with low water-holding capacity soils.

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William R. Argo and John A. Biernbaum

Hybrid impatiens were grown in 15 cm pots containing one of six root medium. After seven weeks, plant available water holding capacity (AWHC) was measured as the difference between the drained weight of the plant and pot after a one hour saturation and the weight of the pot when the plant wilted. Water absorption potential (WAP) was calculated as the capacity of each root medium to absorb applied irrigation water up to the AWHC and was measured at two moisture levels with top watering (two leaching fractions), drip irrigation (two leaching fractions) and flood subirrigation. Top watering moist media (initial AWHC = 35%) with leaching fractions of 30+ % was me most efficient method of rewetting media and was the only irrigation method tested to obtain WAP's of 100%. In comparison, flood subirrigation was the least efficient method of rewetting media with WAP of 27% for dry media (initial AWHC = 0%), and obtained a total WAP of 55% for moist media (initial AWHC = 23%). In media comparisons, the incorporation of a wetting agent into a 70% peat/30% bark mix at planting increased the WAP compared to the same media without a wetting agent with nine of the ten irrigation treatments.

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Michael R. Evans, Giampaolo Zanin, and Todd J. Cavins

properties of substrates are bulk density, total pore space, air-filled pore space, and water-holding capacity. Bulk density refers to the weight of a given volume of substrate and is most commonly reported as grams of dry weight per 100 cm 3 of substrate

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Michael R. Evans and Mary M. Gachukia

compare total pore space (% by volume), air-filled pore space (% by volume), water-holding capacity (% by volume and weight per weight), and bulk density (weight per volume) of sphagnum peat-based substrates amended with various amounts of PBH or perlite

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James S. Owen Jr and James E. Altland

materials and added components. Mechanical analysis ( Dane and Topp, 2002 ) of substrate particle size distribution is routinely performed to make inferences on infiltration, pore size and distribution, and, subsequently, water-holding capacity ( Argo, 1998

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Jeb S. Fields, Kristopher S. Criscione, and Ashley Edwards

. Bark-based substrates often have increased proportions of large-diameter pores, which result in relatively low water-holding capacity (Pokorny, 1979) and allow for ample aeration ( Jackson et al., 2006 ). This is advantageous because it reduces risks

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Johann S. Buck and Michael R. Evans

million tons of fresh rice hulls were produced annually in the United States. According to Bunt (1988) and Hanan (1998) , fresh rice hulls had a bulk density of 0.10 g·cm −3 , water-holding capacity of 20% (v/v), total pore space of 89% (v/v), and an

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Arianna Bozzolo and Michael R. Evans

, vermiculite has been blended with peat as a component to increase substrate water-holding capacity ( Boodley and Sheldrake, 1977 ; Stamps and Evans, 1999 ). Additionally, vermiculite has been commonly used as a top coating material because it is sterile

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John M. Ruter and Hendrik van de Werken

The effect of container design on physical parameters of media with different bulk densities was evaluated. A significant interaction between container design and media for water-holding capacity and air space was found. A container with a polyester fabric bottom had the largest media air space and the smallest water-holding capacity after 24 h of drainage when placed on a column of sand to allow for free drainage from the container medium. For the media tested, a blend of composted pine bark and hardwood bark (PB:HB) appeared to have good physical characteristics for a container medium in the container designs that were evaluated. Container design should be considered when selecting a container medium because physical parameters of a given medium will be influenced.

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W. C. Fonteno, D. K. Cassel, and R. A. Larson


Three fundamental different media 3 pine bark (≤ 6mm): 1 sphagnum peat moss:l concrete grade sand; 2 loamy soil: 1 peat moss: 1 perlíte; and a peat-lite mix, (Metro Mix 350) were characterized by available water-holding capacity, bulk density and particle size distribution. All 3 media provided adequate water-holding capacities for container production of ‘Eckespoint C-1 Red’ and ‘Annette Hegg Diva’ poinsettias (Euphorbia pulcherrima Klotzsch ex. Willd.). Total porosity declined and bulk density increased in all media 9 weeks after potting due to shrinkage but there were no additional changes after an additional 4 weeks. Airspace and water buffering capacities did not change during the 13-week period indicating the loss in total porosity resulted in a loss of easily available water. Water release had linear and nonlinear components with respect to moisture tension. Poinsettia root systems appeared to be extensive throughout the growing media; root distributions varied with cultivar and medium.