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  • Author or Editor: R. A. Larson x
  • Journal of the American Society for Horticultural Science x
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Abstract

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.

Open Access

Abstract

Moisture retention data were collected for five porous materials: soil, phenolic foam, and three combinations of commonly used media components. Two mathematical functions were evaluated for their ability to describe the water content–soil moisture relationship. A cubic polynomial function with linear parameters previously used on container media was compared to a closed-form nonlinear parameter model developed to describe water conductivity in mineral soils. In most tests for precision, adequacy, accuracy, and validation, the nonlinear function was superior to the simpler power series. The nonlinear function provides an excellent tool for describing the water content for media with widely varying physical properties.

Open Access

Abstract

Handling and preparing growing media can have pronounced effects on the “intensity variables” bulk density and equilibrium volume wetness through changes in pore size distribution. These changes in turn affect the container “capacity variables”: the absolute amounts of medium, air, and water in a container. A nonlinear moisture retention function was combined with container geometry in an equilibrium capacity variable (ECV) model that provided accurate predictions of total porosity, container capacity, air space, unavailable water, available water, and solid fraction for several container-medium combinations.

Open Access

Abstract

Plants grown in small containers often show limited growth due to low levels of aeration and water holding capacity in the medium. These levels can be changed by management practices such as medium compaction, medium wetness at time of container filling, container height and volume, peat : vermiculite ratio, particle size, and the use of a wetting agent. A modified equilibrium capacity variable model was applied to an investigation of media-container interactions for short containers (<5 cm tall). Predicted volume percentages for total porosity (TP), container capacity (CC), air space (AS), unavailable water (UW), and available water (AW) were developed from measured moisture retention data and container geometry. AS increased with: 1) increased particle size, 2) increased media moisture at time of container filling, 3) decreased medium compaction, 4) increased wetting agent concentration, 5) decreased ratio of peat : vermiculite, and 6) increased container height. Increased percent AW resulted from smaller particle size, increased media moisture at time of container filling, decreased container compaction, decreased wetting agent concentration, increased ratio of peat : vermiculite and decreased container height.

Open Access

Abstract

Pinched plants of Chrysanthemum morifolium Ramat. ‘Orange Bowl’ and ‘Surf’ grown in a chamber maintained at 22° day/18°C night were transferred to 30° day/26° night at the beginning of week 1, 3, 5, or 7 after start of photoinduction period (15-hr nyctoperiod). Plants remained at high temperatures for 2, 4, 6, 8, or 10 weeks and then were returned to the 22°/18° chamber. Exposure to high temperatures during the first 4 weeks of short days increased the number of nodes, leaf area, stem length, and dry weight of leaves and stems. Rate of floret initiation and perianth differentiation decreased when exposed to high temperatures during the first 4 weeks of short days in ‘Orange Bowl’ but not in ‘Surf’. ‘Orange Bowl’ exposed to high temperatures for 10 weeks from the start of short days flowered 12 days later than plants grown at lower temperatures and formed bracteate buds. Flowering of ‘Orange Bowl’ grown at 22718° during the first 4 weeks of short days, then transferred to high temperatures, was not substantially delayed and flowers developed normally. Flowering was delayed 3 days when ‘Surf’ was exposed to high temperatures for 8 weeks from the start of short days. Exposure to high temperatures did not cause bracteate bud formation in ‘Surf’. With both cultivars, increasing the duration of high temperature exposure increased the time to flowering.

Open Access

Abstract

Experiments were conducted on the Easter lily cultivars (Lilium longiflorum thunb.) Ace and Nellie White over a 4-year period to compare ancymidol bulb dips to media drenches and foliar spray applications. Several bulb dip concentrations and durations were used. ‘Ace’ plants responded more than ‘Nellie White’ plants to bulb dips, primarily because of more natural vigorous growth of ‘Ace’ plants. A 1-hr dip at 33 ppm gave adequate height control, but flowering was delayed. Reliance on bulb dips to achieve optimum height control may be questionable because ancymidol must be applied before one is certain excessive height will be a problem. Chemical name used: α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol).

Open Access

Abstract

Radiation measurements with different types of meters in several controlled environment facilities have been compiled to demonstrate the problems associated with insuring uniform radiation levels in separate faciities. Data are provided for a quantum meter, three photometers, a pyranometer and a far-red energy meter. Significant variations in total radiant energy in chambers under similar photosynthetically active radiation (PAR) levels were demonstrated. Measurement of light under cool white fluorescent and incandescent lighting with calibrated photometers from different manufacturers, varied by 20%. Greater variation occurred when photometer measurements were compared under different types of lamps. One of the most significant variations in different chambers was the intensity of incandescent radiation. This could only be effectively monitored and controlled with the far-red sensor. Factors are given for conversion between quantum, photometric and radiometric measurements, but high precision cannot be assumed in the use of these factors because of the differences in instrument sensitivity and variations in spectral output of lamps. The study documents the need for calibration of instruments under the same type of light source that is utilized in the growth chambers and for the use of more than one type of sensing instrument to quantify the radiation that controls plant growth.

Open Access