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  • Author or Editor: Douglas C. Sanders x
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The diversity of site-specific management opportunities is demonstrated by the list of topics and speakers we have in the colloquium. These techniques will help use to better understand, adapt, and adjust horticultural management to the benefit of producers, researchers, and the consumer. With these technologies we will be able to reduce costs, environmental impacts, and improve production, and quality. Horticulture will use more both remote and manually operated devices that allow more intensive planning and management of our production systems. This colloquium has just scratched the surface of the potential of these techniques in horticulture. We hope that the sampling will whet your appetite for great depth of study of the opportunities that are just around the corner.

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The efficacy of undercutting as a technique to control bolting of two short-day onion cultivars was studied in controlled-environment chambers. `Buffalo' and `Granex 33' onions were grown to the third, fifth, and seventh visible leaf stages in a 10-hour photoperiod at 22/18 °C (day/night) and then exposed to 30, 40, 50, 60, or 70 days of vernalizing temperatures (10/10 °C). Half of the plants were undercut at the initiation of the vernalizing treatment. After vernalizing treatments, plants were returned to 14-hour photoperiods at 22/18 °C. `Buffalo', which is resistant to bolting, did not flower significantly under any of these conditions. The flowering response of `Granex 33' increased with leaf number at vernalization and as the duration of vernalization increased. Undercutting `Granex 33' increased the days of vernalization required for flowering and reduced the proportion of flowering relative to controls. Overall dry-matter accumulation was unaffected by leaf number at vernalization or the duration of vernalization but was reduced ≈30% by undercutting. In both cultivars, fresh mass per bulb decreased with increasing leaf stage of vernalization and number of vernalizing days. Undercutting also decreased fresh mass per bulb, but through its effect on bolting, undercutting increased marketable yield for plants vernalized and undercut at the fifth and seventh leaf stages.

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The effects of fertilizer placement and soil moisture level on soil N movement, uptake, and use by tomato plants (Lycopersicon esculentum Mill) grown with drip irrigation and plastic mulch were evaluated at two locations on two types of sandy soils. Broadcast or band fertilizer placement had no effect on fruit size, fruit number, or total yield. Fruit size was increased at one location, and the incidence of blossom-end rot was decreased by increased frequency of irrigation. Nitrate-N distribution within the bed was not affected by initial N placement. In the soil with a rapid infiltration rate, NO3-N levels in the center of the bed were always low, with highest concentration observed in the areas of the bed most distant from the drip tube. In the soil with the slower infiltration rate, NO3-N concentrations were more uniform throughout the bed, with highest concentrations in the bed center: Increasing soil moisture levels (–20 kPa vs. –30 kPa) resulted in increased leaching and reduced NO3-N concentration throughout the bed. Foliage N concentration was not affected by N placement, but decreased seasonally. Total N uptake by the above-ground portion of the plants was not affected by fertilizer placement or soil moisture level.

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Many potential students, because of distance from the University campus and/or job requirements, cannot take traditional courses on-campus. This group of learners is place-bound—a group of learners who may be employed full-time, most-likely married with job responsibilities and/or other situations demanding most of their attention. These persons are the very definition of nontraditional, and their educational needs demand non-traditional pedagogy. Their maturity and self-directedness eliminate many concerns often voiced about extending support and evaluation inherent in maintaining quality for and among students adopting Distance Education (DE). In North Carolina, the audience is large and demands that the University reach out to them. Cooperative Extension's more than 120 Horticultural Crops Extension Agents (field faculty) and over 300 other field faculty whose interests include horticultural topics constitute students identifiable as likely enrollments for credit taking hours off-campus. Distance Education can overcome these problems in several ways. First, high demand, low-seat-available classes can offer additional enrollment for credit if open to Distance students. Second, courses can be offered asynchronously or with alternative delivery. Finally, courses offered collaboratively among institutions generate a level of interest and enthusiasm that may not exist for home-grown courses. Such efforts as these are creating a Distance Education program in NCSU's Horticultural Science Department.

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Studies were conducted to determine the effect of N application frequency through drip irrigation on soil NO3-N movement in the bed profile and on yield and N uptake by tomato plants (Lycopersicon esculentum Mill. `Sunny') at two locations. Increasing N application frequency resulted in increased yields at Clayton, N. C., but not at Charleston, S.C. The number of fruit produced was not affected by N treatment at either location, but fruit size increased with increasing N application frequency at Clayton. Foliage N concentration decreased seasonally, but neither foliage N concentration nor total N content of the above-ground portion of the plants was affected by N application frequency. Regardless of N application frequency, NO3-N concentrations within the raised bed decreased with time due to plant uptake and leaching. Nitrogen levels declined most rapidly in the area closest to the drip tube.

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Two formulations of a new methylene urea product on tomato were evaluated. Applications of 150, 200, 250 lb/acre of N in eastern North Carolina and 175 and 250 lb/acre of N in western North Carolina of both liquid and dry formulation of the material were made. The liquid was applied the first 6 weeks of growth and the dry applied at planting. These treatments were compared with 200 lb/acre of N (standard) and 300 lb/acre of N, which were fertigated throughout the season. In eastern North Carolina, all rates of the liquid and high rate of dry formulations produced more yield of larger fruit than the standard. In western North Carolina, all methylene urea sources out-performed the standard. Soil and foliar nitrate was somewhat greater than the standard throughout the season, but, at end of season in the west, only the 250 dry material had more N in the soil. Methylene urea treatments took up more N than the control. All methylene urea except 200 dry produced more dollars per acre than the standard.

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Abstract

‘Jackpot’ tomatoes (Lycopersicon esculentum Mill.) were grown in 6 plant protection systems with or without black polyethylene mulch. Mulching increased early and total yield of large and marketable fruit and increased total yield of cull fruit. Row covers reduced early yield of large fruit and average large fruit weight. Use of large transplants from 7.5-cm square peat pots tended to increase early marketable yield but decreased early and total average large fruit weight as compared to performance without a plant protection system.

Open Access

This study was conducted to compare different formulations of a slow-release fertilizer with a conventional fertilizer program to determine their impact on yield and growth of bell pepper (Capsicum annuum). Two formulations of a methylene-urea slow-release fertilizer (Nitamin®) were evaluated on drip-fertigated and plastic-mulched bell peppers during 2006 in the eastern coastal plain and western Appalachian mountains of North Carolina. Liquid slow-release formulations were applied the first 6 or 9 weeks of the growing season and a dry formulation was banded at planting. Treatments were compared with the extension-recommended rate of 200 lb/acre nitrogen (N) (NC-200) and a high-input fertilizer rate of 300 lb/acre N (HI-300) from calcium nitrate injected in 12 weekly applications of drip irrigation. Irrigation was applied twice per week. The slow-release granular formulation at 200 lb/acre N produced the highest marketable yield and better canopy quality in eastern soil. Early marketable yield for this treatment accounted for 46% of the total yield. All slow-release treatments had higher N use efficiency (NUE) values than NC-200 and HI-300 in the eastern study. In loam soil (western study), pepper yield was statistically similar among treatments. Lower rates (150 lb/acre N) of slow-release fertilizer performed as well as NC-200 and HI-300 for marketable yield. Low rates (150 lb/acre N) of one of the liquid formulations performed better in total and marketable NUE than NC-200 and HI-300 in Fletcher, North Carolina. Liquid and dry formulations of slow-release fertilizer showed a potential to be used on bell pepper production across the state at reduced N rates, with greater impact on yield in coarse-textured soils found predominantly in the eastern coastal plain region.

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Two crack-resistant and two crack-susceptible fresh-market tomato (Lycopersicon esculentum Mill.) cultivars were evaluated at varied soil moisture levels for physiological fruit defects and yield. Cultural practices recommended for staked-tomato production in North Carolina with raised beds, black polyethylene mulch, and drip irrigation were used. Soil moisture levels of less than −15.0, −30 to −40, and greater than −70 kPa were maintained and monitored using daily tensiometer readings. Soil moisture level had no effect on fruit cracking, blossom-end rot, zippers, or yield. However, there-were large differences among cultivars for fruit defects and total and marketable yields.

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We determined if application of certain naturally occurring compounds would stimulate emergence, growth, and development of carrot (Daucus carota L.). The commercially available biostimulants Agro-Lig, Enersol (humic acids), and Ergostim (folic acid) were added at a concentration of 1.5% (w/v) to Laponite 508 (magnesium sulfate) gel used in fluid drilling. Agro-Lig, Enersol and Ergostim increased carrot emergence > 2-fold as measured by number of roots as compared to untreated seed. Number of carrots increased 50% to 75% when biostimulants were incorporated into the gel, compared to fluid-drilled seed without the biostimulants. When biostimulants were applied as a drench over untreated seeds sown conventionally, the average root weight obtained was more than twice that from untreated seeds.

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