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Daniel I. Leskovar, Daniel J. Cantliffe, and Peter J. Stoffella

Studies were conducted to evaluate growth of tomato (Lycopersicon esculentum Mill.) transplants in the field in response to age of transplants in Spring and Fall 1989. Transplants were 2 (2W), 3 (3W), 4 (4W), 5 (SW), or 6 (6W) weeks old. Drip and subseepage irrigation were used. In spring, older transplants produced more shoot and root growth up to 2 (T2) weeks after transplanting. At 3 (T3) and 4 (T4) weeks after transplanting, there were no differences between 4W, 5W, and 6W transplants. These trends were independent of irrigation systems. Total yield and early yield were similar for all transplant ages. In fall, shoot growth increased linearly with increasing transplant age at TO, but not thereafter. Chlorophyll a + b increased over time, but no treatment differences were found at T4. At planting, 2W transplants had a higher Chl a: b ratio than older transplants. This difference was reduced at T1 and T2 and became insignificant at T4. These results indicate that no improvement in yields was obtained using the traditional older transplants. Younger transplants might be used to achieve rapid seedling establishment with-minimal transplant production costs.

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Joyce G. Latimer and Ray F. Severson

Epicuticular waxes were analyzed to explain the visible differences in the waxy bloom of conditioned broccoli (Brassica oleracea L. Group Italica `Green Duke') transplants. Seedlings (22 days old) were subjected to brushing (40 cycles per minute, 1 minute twice daily), wind (7 m·s-1 for 5 minutes twice daily), or moisture-stress conditioning (MSC; visible wilt for 2 to 4 hours daily) for 16 (1987) or 21 (1988) days during transplant production in the greenhouse. The epicuticular waxes of the uppermost fully expanded leaves were removed by dipping detached leaves into methylene chloride. The extract was derivatized with trimethylsilyl reagents and subjected to capillary gas chromatography. The primary epicuticular wax components were the nonpolar C29 compounds nonacosane, nonacosan-15-ol, and nonacosan-15-one, which were identified by mass spectrometry. In a Summer 1987 experiment, cuticle samples taken over time of treatment indicated acclimation to the conditioning treatments relative to untreated plants. After 9 days of treatment, the amount of total epicuticular waxes present on the leaves was reduced 38%, 31%, or 11% by wind, brushing, or MSC, respectively. However, after 15 days of treatment, the amount of cuticle present was reduced 15% by brushing but only 6% by wind and was 17% greater in MSC-treated plants. Two weeks after transplanting to the field there were no differences in the amount or composition of the epicuticular waxes. In Fall 1988, all treatments reduced plant growth, but only MSC tended to increase the amount of C29 epicuticular components during greenhouse production. Differences in the amounts of epicuticular waxes were no longer significant after 8 days in the field.

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Chieri Kubota, Haruna Maruko, and Toyoki Kozai

For vegetative propagation of sweetpotato, single or multi-node leafy cuttings are used as propagules. A quantitative understanding of leaf development is important for predicting the number of propagules produced after a given production period under various environmental conditions. For plant production in a relatively closed structure, controlling CO2 concentration is necessary, but effects of CO2 concentration on cutting production rates of sweetpotato are not well-investigated. Single-node cuttings each with a fully expanded leaf (the initial leaf blade length was 66 mm) were grown under one of three levels of CO2 concentration (400, 800, and 1200 μmol·mol-1), 250 μmol·m-2·s-1 PPF, 16 h/day photoperiod, and 29 °C air temperature. The plant dry weight increased faster in the higher CO2 concentrations. Changes in the number of harvestable cuttings during the production period was defined by changes in the number of leaves reaching a leaf blade length (LBL) longer than a given standard length (LS). The number of harvestable cuttings increased almost linearly with time after the LBL of the first leaf reached the LS, regardless of CO2 concentration. The effect of CO2 concentration on cutting production rate (number of harvestable cuttings per day) was varied with different LS. For example, at LS = 20, 30, and 40 mm, the cutting production rate increased slightly at higher CO2 concentrations, while at LS = 60 mm, it decreased significantly at higher CO2 concentrations. This indicates that, under the present experimental conditions, increasing CO2 concentration increased the number of small leaves that might not be usable as cuttings (propagules). Environmental control is necessary in vegetative propagation to increase the number of propagules and the biomass usable as propagules, thereby minimizing energy and resources needed for the propagule/transplant production process.

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Andrew Jeffers, Marco Palma, William E. Klingeman, Charles Hall, David Buckley, and Dean Kopsell

Production of high-quality nursery liners has long been a foundation principle for enabling success and business longevity in the competitive nursery industry. Unfortunately, many different characteristics can be used to define liner “quality,” ranging from physiological parameters measurable in scientific studies field establishment success and transplant production performance to gut-level hunches on the part of growers. A more complete understanding of what buyers are looking for in a bare-root liner would significantly enhance the success of producers in meeting the demands of end-users. As a result, a choice study involving a point-of-purchase simulation was designed to assess preferences of green industry professionals when viewing bare-root 1 + 0 nursery liners. A conjoint design was used for this study and involved six key attributes of liners: 1) number of first-order lateral roots (FOLR); 2) price; 3) production region; and uniformities of 4) height; 5) canopy density; and 6) liner caliper. A visual survey based on a large, color graphic depicting six distinct bare-root 1 + 0 liners with different combinations of attributes was administered together with a demographic questionnaire at four different green industry tradeshows and extension grower education and outreach venues in the southeastern United States. Results from 248 completed surveys corroborated previously reported results suggesting that high FOLR is the most important attribute influencing preference for 1 + 0 liner products followed by uniform liner height and canopy density. Contrary to a priori expectations, neither price nor region of production substantially influenced product preference. Utility values were calculated for each attribute level using outputs from the experimental model. These values can be used by growers to adjust production methods to improve liners with attributes that end-users value most. In addition, growers will be able to better estimate product ratings, redirect marketing efforts, and assess sales potential for various bare-root 1 + 0 liner products in U.S. markets.

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Lauren C. Garner and Thomas Björkman

Stretching is a problem in high-density transplant production. Mechanical conditioning provides good height control for many crops, but information concerning the dosage and timing of stimulation, and possible effects on field performance are necessary for successful commercial implementation. Mechanical conditioning was applied to processing tomatoes (`Ohio 8245') grown in #288-deep flats (≈2000 plants/m2). Brushing was applied by daily gentle stroking of the plant canopy with a Styrofoam planter flat. The appropriate dose as determined by stroking 0, 10, 20, or 40 times daily back and forth. Twenty strokes provided sufficient height control with minimal plant damage. The interval between strokes was also varied, using 0.6 6, 60, or 600 s. These intervals were all equally effective in reducing the growth rate of the canopy. This broad range provides flexibility in commercial use of this technique. To test for effects on field performance, two methods of conditioning were used: brushing and impedance. Brushing was 20 continuous strokes daily. The impeded plant canopy was compressed slightly by a piece of Plexiglas suspended overnight. The treatments were applied from canopy closure until transplanting to the field. At transplanting, brushed and impeded plants were significantly shorter than control plants without a reduction in shoot dry weight. The treatments did not affect the speed at which the plants grew in the field. Within 5 weeks after transplanting, there were no significant differences between treatments in any measured parameter, including final yield. Therefore, both brushing and impedance provide a flexible and effective method for controlling tomato transplant height without adversely affecting establishment or yield.

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V.M. Russo

Commercially produced bare-root onion (Allium cepa L.) transplants may not be uniform in size and require a period following planting in which to begin regrowth. There is little information on how, when established in the field, plants developed from greenhouse grown onion transplants differ from those that develop from bare-root transplants. Development and yield for onions grown from bare-root transplants were compared to plants produced from transplants grown in single cells with volumes of 36 or 58 cm3 in seedling production trays in a greenhouse. `Texas Grano 1015Y' and `Walla Walla' onions were established in the field with commercially available bare-root transplants or with greenhouse grown transplants produced in trays. Bare-root transplants were heavier than 8-week-old greenhouse grown transplants. Fresh weights of transplants produced in 58-cm3 cells were heavier than those from 36-cm3 cells, but dry weights were similar. From when about 20% of onion tops were broken over, onion bulb diameters did not increase sufficiently to justify delaying harvest until 50% of tops had broken over. Yields of `Walla Walla' were better than those of `Texas 1015 Y' and yields from plants developed from seedlings grown in 58-cm3 cells were similar to those from plants developed from bare-root transplants and better than those from plants developed from seedlings grown in 36-cm3 cells. Individual bulb weights of `Texas 1015 Y' were not affected by transplant type and averaged 162 g. Individual bulbs for `Walla Walla' from plants developed from bare-root transplants and those produced in 58-cm3 cells were similar in weight (averaged 300 g) and were heavier than those from plants developed from transplants grown in 36-cm3 cells (240 g). Greenhouse transplants produced in trays with the larger cells may provide an alternative to the use of bare-root transplants, if transplant production costs are comparable.

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Janet F. Miles and Mary M. Peet

`Grace' tomatoes were grown utilizing three different growing methods: organic, conventional, and biorational (IPM and use of reduced-risk pesticides). There was one treatment per greenhouse per growing season. Treatments were rotated for each crop. Inputs for the organic system were allowable according to the Carolina Farm Stewardship Materials List for organic certification or the Organic Material Review Institute (OMRI). Organic methods were compared to conventional and biorational methods in a total of two spring and two fall crops. The conventional and biorational substrates consisted of a commercial peat/perlite blend containing a “starter” nutrient charge. The organic substrates were a coir pinebark blend and a peat/perlite/vermiculite commercial substrate without non-organic “starter nutrients” and wetting agents. Organic substrates were amended with 15% by volume vermi-compost and dolomitic lime. Organic nutrient amendments were bloodmeal, bonemeal, and potassium sulfate to provide an initial nutrient charge. Organic post-transplant fertilization practices included three commercial blends used at several application rates. Fertilizers were applied by “mixing and pouring” in Spring 1998, but were injected into the drip irrigation system for the remaining three growing seasons. Data was collected on harvest yield, fruit quality, and plant development. In the first two growing seasons, organic production resulted in the highest percentage of number1 quality fruit, but in Spring 1998, these plants were developmentally slow, resulting in lowest total yields. In the Fall 1998 and Spring 1999 crop, all measurements of growth and yield for organic production were comparable to those in conventional and biorational controls. We feel however, that additional development work is required in the organic treatments to optimize transplant production, post-plant fertilization regimes and biocontrol application.

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Susan L. Barkley, Sushila Chaudhari, Jonathan R. Schultheis, Katherine M. Jennings, Stephen G. Bullen, and David W. Monks

There is a research gap with respect to documenting the effects of sweetpotato (Ipomoea batatas) seed root density and size on transplant yield and quality. Field studies were conducted in 2012 and 2014 to determine the effect of sweetpotato seed root (canner size) density [12, 24, 37, 49, 61, 73, and 85 bushels [bu (50 lb)] per 1000 ft2] on ‘Covington’ and ‘Evangeline’ slip production in propagation beds. Another field study was conducted in 2012 and 2013; treatments included canner, no. 1, and jumbo-size ‘Covington’ roots at 49 bu/1000 ft2, to determine the effect of seed root size on slip production. As seed root density increased in the propagation bed, transplant production increased with no change in slip quality as measured by node counts and slip length except for stem diameter. In 2012, the best marketable slip yield was obtained at root densities of 73 and 85 bu/1000 ft2. In 2014, marketable slip production of ‘Evangeline’ increased as seed root density increased at a greater rate than ‘Covington’. In 2014, the best seed root density for marketable slip production was 49 to 85 bu/1000 ft2 for ‘Covington’ and 85 bu/1000 ft2 for ‘Evangeline’. In 2012, potential slip revenues increased with an increase in seed root density up to 73 bu/1000 ft2. In 2014, revenue trend was similar for ‘Covington’ as 2012; however, for ‘Evangeline’, revenue was greatest at 85 bu/1000 ft2. Seed root size had no effect on marketable slip production when using a once-over harvest system. Results suggest growers would use a seed root density from 49 to 85 bu/1000 ft2 depending on variety, and any size roots for production of optimum marketable slips. Selection of optimum seed root density also depends on grower needs; e.g., high seed root density strategy will have a higher risk due to the upfront, higher seed costs, but potentially have higher profits at harvest time. Lower seed root density strategy would be a lower initial risk with a lower seed cost, but also potentially have lower net revenues.

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William J. Lamont Jr

transplant production and greenhouse crop production. The transplant production section is an excellent source of information on all aspects of growing vegetable transplants, including containers, seeds, temperatures, time requirements, mixes, fertilizers

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Juan Carlos Diaz-Perez, W. Keith Jenkins, Dharmalingam Pitchay, and Gunawati Gunawan

For premium quality transplant production, it is critical to provide balanced and complete nutrition before and after seed germination. In organic production systems, nutrient management is complex and variable, unlike in inorganic production