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Open access

L. Art Spomer

Abstract

This paper describes a simple laboratory exercise for demonstrating the direct relationship between container soil volume and plant growth in a way that avoids complications caused by soil geometry (shape and depth). This is accomplished by mixing different amounts of gravel into each container soil thereby excluding different volumes of soil from otherwise identical containers.

Open access

L. R. Nelms and L. Art Spomer

Abstract

Water stress resulting from inadequate soil water retention following transplanting is a major cause of container-grown transplant failure. The relatively small water supply contained in the soil containers used in nursery and bedding plant production is reduced further by enhanced drainage following transplanting. This drainage phenomenon, which has received little previous attention, was investigated under controlled laboratory conditions. Samples of 2 suitable container soils were embedded in simulated ground bed soil and retained in a container; water retention of the embedded soil, surrounding ground bed soil, and contained soil was monitored simultaneously to determine if the embedded soil (analogous to a container-grown transplant’s soil) retained less water than the contained soil. The embedded soils lost 30% to 85% of their estimated available water within a few hours, whereas contained soils lost the same quantity only after 3 or 4 days of surface evaporation. A simultaneous increase in water content in the surrounding ground bed soil indicated that the rapid water loss from the embedded soil was due to water movement into the surrounding soil. A similar water loss following subsequent irrigation of the embedded and ground bed soils indicated that this embedded soil water loss is primarily a drainage phenomenon. This effect was concluded to be a potentially significant factor affecting transplant survival.

Open access

L. Art Spomer

Abstract

The soil water distribution pattern in a container soil is simulated using cellulose sponges as an analog of container soils. Two classroom exercises are presented that have been successful in both classroom and extension presentations to horticulturists.

Open access

L. Art Spomer

Abstract

The quantity of amendment required to ensure adequate aeration in container soils is usually determined by empirical tests on a series of mixtures containing different amounts of the amendment In this study, the “threshold proportion” or minimum amount of amendment required before aeration improvement begins, was demonstrated to be controlled by amendment interporosity. This concept is the basis for a method of predicting total and aeration porosity of any container soil mixture.

Open access

David R. Hershey

Abstract

One of the most important aspects of the physics of growing media in containers is the limited bulk volume of the medium (2,4). Bulk volume (BV) includes the volume of the medium solids and pore spaces (1). Despite the importance of BV in determining the amounts of air, water, and nutrients in the pot, BV is rarely specified in research articles involving plant growth in container media. Without BV, volumetric properties, such as bulk density (g/ml), container capacity (percent by volume), air-filled porosity (percent by volume) and fertilization and liming rates (kg/m3), cannot be converted to absolute amounts per pot. The purpose of this study was to develop equations to calculate BV using pot dimensions and medium height in the pot.

Free access

Daniel C. Bowman, Richard Y. Evans, and Linda L. Dodge

A study was conducted to determine the potential for using ground automobile tires as a container medium amendment. Rooted cuttings of chrysanthemum [Dendranthema × grandiflorum (Ramat.) Kitamura] were planted in 1.56-liter pots containing 1 sand:2 sawdust (v/v) or media in which coarsely or finely ground particles of rubber substituted for 33%, 67%, or 100% of the sawdust. Amendment with the coarse material decreased total porosity and container capacity and increased air-filled porosity and bulk density relative to the sawdust control. Amending the medium with the fine material did not appreciably alter total porosity, container capacity, or bulk density, but did increase air-filled porosity. Plant height, fresh weight, dry weight, and number of open flowers were reduced significantly in rubber-amended media compared to sawdust controls. Rubber amendment reduced shoot tissue concentrations of N, P, K, Ca, Mg, and Cu, but increased Zn as much as 74-fold over control values. There was no accumulation of other heavy metals (Cd, Cr, Ni, Pb) or Na in the tissue due to rubber amendment. This study demonstrates that ground tires might be used as a component of container media in the production of greenhouse chrysanthemums. However, growth reductions and the potential for Zn toxicity may limit the usefulness of ground tires as a substitute for conventional organic amendments.

Full access

Timothy S. Prather, James J. Stapleton, Susan B. Mallek, Tarcisio S. Ruiz, and Clyde L. Elmore

A double-tent solarization technique, which accumulates higher soil temperatures than solarization of open fields, was recently approved by the California Department of Food and Agriculture (CDFA) as a nematicidal treatment for container nurseries. Due to the need for broad-spectrum pest control in container nursery settings, this technique was tested to determine its usefulness as an herbicidal treatment. Laboratory-derived thermal death dosages (temperatur × time) for several weed species important in California, including common purslane (Portulaca oleracea), tumble pigweed (Amaranthus albus), and black nightshade (Solanum nigrum), were previously determined and the data were used as guidelines for devising treatment duration in this study. In two field experiments conducted in 1999 and 2000 to validate the laboratory data, moist soil was placed in black polyethylene planting bags [3.8 L (1 gal) volume], artificially infested with seeds of the three test species, and subjected to 0 to 24 hours of double-tent solarization after reaching a threshold temperature of 60 °C (140 °F) (about 1.5 to 2.0 h after initiation of the experiment). In 1999, samples were removed at 2, 4, 20, and 24 hours after reaching the 60 °C threshold, then incubated to ameliorate possible secondary dormancy effects. Seeds failed to germinate in any of the solarized treatments. In 2000, samples were removed at 0, 1, 2, and 6 h after reaching 60 °C. Again, apart from the nonsolarized control treatment, all weed seeds failed to germinate at any of the sampling periods, in accordance with prior laboratory thermal death results. Reference tests to estimate effects of container size on soil heating showed that soil in smaller container sizes (soil volume) reached higher temperatures, and were maintained at high temperature [above 60 °C (140 °F)] for a longer period of time, than larger container sizes. The double-tent solarization technique can be used by commercial growers and household gardeners to effectively and inexpensively produce weed-free soil and potting mixes in warmer climatic areas.

Open access

L. Art Spomer

Abstract

Soil physical amendment (soil mixing) is a widespread horticultural practice. Unfortunately, it is often done with little understanding of the principles involved or the physical effects produced. Three simple demonstrations are described which have proved helpful in explaining the physical effects of soil amendment in classroom and extension presentations. These exercises use simple volume measurements and require commonly available supplies including containers, a volume measure, a sieve, plastic sheets, and media components such as soil and sand. The differences between component and mixture water retention are used to demonstrate the effect of amendment on porosity, water retention, and aeration. Some sample results and discussion questions are included.

Open access

Norman E. Pellett and Donald B. White

Abstract

Roots of container grown ‘Hetzi’ juniper developed cold hardiness to -10°C on December 2, 1963 in St. Paul, Minnesota as determined by controlled freezing tests. The temperature of container soil, under natural conditions, did not fall below 0° until after December 2. Once frozen, the soil temperature responded rapidly to falling ambient temperatures. Container soil temperatures of -10° occurred several times after December 2 resulting in root injury.

Tops developed cold hardiness from -15°C on September 11 to greater than -39° on December 2, 1963. No top injury occurred at any stage during the study. Winter injury common to container grown Hetzi Juniper in Minnesota is apparently root injury.

Open access

Steven C. Wiest, George L. Good, and Peter L. Steponkus

Abstract

Equal average container temperatures during prolonged periods of low outside air temperatures were achieved by unheated structures covered with either a double-layer of clear polyethylene or a double-layer with the inner layer translucent and the exterior clear polyethylene. Single-layer structures were less effective, with clear polyethylene affording more protection than translucent. Excessively high mid-day temperatures in both the single- and double-layer clear houses increased the probability of desiccation injury and affected the quality of the nursery stock. Fluctuations of air temperatures below 0°C were most rapid in the clear houses, and appear to depend greatly on the relative humidity, which affects the thermal conductivity of the air. Container temperature fluctuations were similar whether the container soil water was frozen or unfrozen. The best covering tested thus far appears to be a double-layer with the interior translucent and the exterior clear polyethylene. This covering moderates low container temperatures, high mid-day temperatures, desiccation problems, rapid temperature fluctuations and concomitant management problems.