Environmentally compatible production practices are conscious efforts to design and retrofit nursery container growing areas to improve irrigation and nutrient efficiency, and reduce exposure of ground and surface water supplies to contaminated effluent. Irrigation of ornamental crops in containers can be very inefficient, using large quantities of water and fertilizer. Irrigation water and fertilizer use efficiencies are directly related to each other. Improving irrigation efficiency improves nutrient efficiency and reduces water volume and nutrients leaving production beds. Increasing efficiency can be accomplished in many ways. Grouping plant species and container sizes into blocks with similar water requirements improves efficiency. Redesigning overhead sprinkler systems to accomplish uniform distribution across growing beds or replacing worn nozzle orifices can significantly reduce application variability. Low volume/low pressure systems that distribute water directly into containers and apply less water in a specific amount of time compared to overhead sprinkler application, will conserve water. Applying irrigation in short cycles rather than long cycles improves wetting in substrates and conserves electrical energy, water and directly reduces nutrient leaching from containers. Creating microclimates in nurseries to optimize light or reduce container temperatures, disease pressure and crop stress can improve water and nutrient efficacy. Flow of water running off growing areas must be engineered to slow velocity, filter and contain effluent. Strategies should be site-specific. Capture, containment and recycling of irrigation water has been a common practice in many nurseries in the U.S., as a means to provide adequate water supplies. Vegetative filter strips adjacent to beds and containment basins have been installed at nurseries to reduce contaminants in runoff before water enters recycle irrigation supplies. In areas with sandy soils, some nurseries have developed closed systems where drainage channels and collection basins are lined to prevent nitrogen movement from runoff into shallow groundwater.
Ted E. Bilderback and Paul R. Fantz
Stuart L. Warren and Ted E. Bilderback
Irrigation of container-grown ornamental crops can be very inefficient, using large quantities of water. Much research was conducted in the 1990s to increase water efficiency. This article examined water management, focusing on three areas: water application efficiency (WAE), irrigation scheduling, and substrate amendment. Increases in WAE can be made by focusing on time-averaged application rate and pre-irrigation substrate moisture deficit. Irrigation scheduling is defined as the process of determining how much to apply (irrigation volume) and timing (when to apply). Irrigation volume should be based on the amount of water lost since the last irrigation. Irrigation volume is often expressed in terms of leaching fraction (LF = water leached ÷ water applied). A zero leaching fraction may be possible when using recommended rates of controlled-release fertilizers. With container-grown plant material, irrigation timing refers to what time of day the water is applied, because most container-grown plants require daily irrigation once the root system exploits the substrate volume. Irrigating during the afternoon, in contrast to a predawn application, may increase growth by reducing heat load and minimizing water stress in the later part of the day. Data suggest that both irrigation volume and time of application should be considered when developing a water management plan for container-grown plants. Amending soilless substrates to increase water buffering and reduce irrigation volume has often been discussed. Recent evidence suggests that amending pine bark substrates with clay may reduce irrigation volume required for plant production. Continued research focus on production efficiency needs to be maintained in the 21st century.
Ted E. Bilderback and Mary R. Lorscheider
Packaged commercial grower mixes routinely contain wetting agents. Studies report that dry components such as pine bark can be more thoroughly moistened if wetting agents are used. Under frequent leaching irrigations, wetting agents have been reported to enhance nutrient loss. Effective longevity is expected to be only 3 to 4 weeks. New products claim greater longevity and advertise that less water volume is required for optimum plant growth. One such product is Saturaid (Debco Pty, Victoria, Australia). The objective of this study was to evaluate the effect of Saturaid on physical properties, nutrient levels, and growth under decreasing irrigation volume. The granular wetting agent was incorporated at 0, 1.0, and 2.0 g·liter–1 substrate volume. Cotoneaster dammeri `Skogholm' plants were potted into 2.8-liter pots and irrigated with 500 ml of water for 22 days, after which one-third of the containers received 425 ml (–15%) and one-third were irrigated with 350 ml (–30%) daily. Saturaid had little effect on moisture and air characteristics, and no effect on foliar nutrients or on leachates collected at 43, 64, or 84 days. When irrigation volume was decreased 15%, top dry weight was greatest at 2 g, followed by 1 g of Saturaid. When irrigation volume was decreased 30%, the same results occurred for top and root growth.
Alex X. Niemiera, Ted E. Bilderback, and Carol E. Leda
Pine bark (PB), either unamended or amended with sand (S) at 9 PB: 1 S or 5 PB:1 S (v/v), was fertilized with solutions of 100,200, or 300 mg N/liter solution and tested for N concentration using the pour-through method (PT). PB, 9 PB: 1 S, and 5 PB: 1 S had porosities of 84%, 75%, and 66%, respectively. PT NO3-N concentrations, obtained via PT, of the 5 PB:1 S substrate were 43%,28%, and 15% higher than PB NO3-N values for the 100,200, and 300 mg·liter-1 treatments, respectively. Differences in N concentration obtained with PT can be attributed to substrate physical characteristics. Based on the results, data for PT should be interpreted with regard to substrate porosity.
Chin Chin Lee, Ted E. Bilderback, and Judith F. Thomas
Photoperiod treatments of 10, 12, 14, and 16 hours and a field control were used to determine the photoperiodic response of Heptacodium miconioides Rehd. The F values for vegetative growth responses under various photoperiods exhibited a highly significant linear effect. Leaf count, area, and weight, shoot length, and stem weight were lower for plants exposed to the 10- or 12-hour photoperiod than those of plants grown under the 14- or 16-hour photoperiod or in the field. Plants under the 10- or 12-hour photoperiod became dormant after 5 weeks of treatment. The growth responses for the 10- and 12-hour photoperiods were similar. There also were no differences in growth responses of plants from the 14- and 16-hour photoperiods or from the field. A favorable photoperiod for growth of Heptacodium must exceed 12 hours; thus, it can be classified as a long-day plant in reference to vegetative growth. Leaf tissues under the 10- and 12-hour photoperiods were significantly thicker than those under the 14- and 16-hour periods or under field conditions due to longer cells of the palisade mesophyll layer. Plants grown in the field and under the 14- or 16-hour photoperiods were the only ones that initiated inflorescences. With days at 30C, leaf and stem dimensions were larger than those at 22C. Nights at 18C resulted in a larger leaf area, leaf weight, and stem weight than at 26C. There was a significant effect on total leaf thickness due to day × night temperature interaction.
Robert J. Rouse, Paul R. Fantz, and Ted E. Bilderback
Japanese cedar [Cryptomeria japonica (Thun. ex L.f.) D. Don. (Taxodiaceae)] cultivars have become quite popular in the U.S. landscape and nursery industries. Their popularity is expected to increase as more attractive and adaptable horticultural selections gain recognition. Taxonomic problems include an inadequate inventory of selected variants cultivated in the United States, instability of names at the infraspecific taxonomic level, poor descriptions of the cultivars, and a lack of representative specimens and identification aids to help horticulturists identify unknown specimens. A study of Cryptomeria japonica cultivated in the United States is needed to address these problems.
Robert J. Rouse, Paul R. Fantz, and Ted E. Bilderback
Japanese cedar, Cryptomeria japonica (Thunb. ex L.f.) D. Don [Cupressaceae Bartling, formerly assigned to Taxodiaceae Warm.] is increasing in popularity as a landscape plant in the eastern United States. A taxonomic study of cultivars grown in the eastern United States was conducted. Forty-five cultivars were recognized. Each cultivar bears synonymy, a quantitative morphological description newly described from field data, herbarium vouchers, references to original literature and observational notes. A glossary of taxonomic terms relevant to Cryptomeria is presented. A taxonomic key is presented for segregation of cultivars that should assist professional plantsmen in identification of taxa cultivated in the eastern United States.
Garry J. Bradley, Mari Helen Glass, and Ted E. Bilderback
With the rising cost of sphagnum peat, nurserymen are looking at alternatives for growing substrates. Daddy Pete's plant pleaser is a product of composted cow manure. This study was conducted to see if composted cow manure could be used to grow containerized plants and replace sphagnum peat. Research was conducted using two Rhododendron cultivars, `English Roseum' and `Scintillation'. Plants of each cultivar were potted into 3-gallon containers. Test substrates were tested against the grower's standard mix, 80 pine bark: 20 sphagnum peat (% by volume), amended with 20 lbs Scotts Prokoke, 8 lbs dolomitic limestone, and 1.5 lbs step minor element package/1.7 yard3. Test substrates were treated equally. Daddy Pete's plant pleaser can work as a substitute for peatmoss in a growing mix. The Daddy Pete compost grew just as good a plant as the Buds & Bloom standard. Watering management turns out to be a factor because the compost generally held more water, therefore not needing irrigation as frequently.
Ted E. Bilderback, Stuart L. Warren, James S. Owen Jr., and Joseph P. Albano
Many research studies have evaluated potential organic and mineral container substrate components for use in commercial potting substrates. Most studies report results of plant growth over a single production season and only a few include physical properties of the substrates tested. Furthermore, substrates containing predominantly organic components decompose during crop production cycles producing changes in air and water ratios. In the commercial nursery industry, crops frequently remain in containers for longer periods than one growing season (18 to 24 months). Changes in air and water retention characteristics over extended periods can have significant effect on the health and vigor of crops held in containers for 1 year or more. Decomposition of organic components can create an overabundance of small particles that hold excessive amounts of water, thus creating limited air porosity. Mineral aggregates such as perlite, pumice, coarse sand, and calcined clays do not decompose, or breakdown slowly, when used in potting substrates. Blending aggregates with organic components can decrease changes in physical properties over time by dilution of organic components and preserving large pore spaces, thus helping to maintain structural integrity. Research is needed to evaluate changes in container substrates from initial physical properties to changes in air and water characteristics after a production cycle.