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  • Author or Editor: Mary M. Peet x
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Commercial recommendations exist for using short-term salt-shocks on tomato (Lycopersicon esculentum Mill.) to improve fruit quality. Six experiments were conducted to 1) assess the influence of nutrient concentration and short-term salt-shocks on fruit quality and yield and 2) identify a vegetative predictor of subsequent fruit quality. The first objective was addressed in three nutrient film technique (NFT) experiments (Expts. 1-3). Four treatments were applied: two maintained constant at two baseline concentrations (0.25X and 1X-commercial level) and two provided salt-shock periods of 30 min, twice daily. There were no effects of baseline concentration or salt-shocks on total number and weight of marketable fruit. Fruit quality was better at the 1X baseline concentration as observed by higher titratable acidity (Expt. 2), higher percent dry matter (Expts. 2 and 3), higher soluble solids concentration (Expt. 2), and lower pH (Expts. 2 and 3), however, weight per marketable fruit was lower (Expt. 2). Salt-shocks had little effect on fruit quality, refuting its commercial potential. Salt-shocks decreased fruit pH (Expts. 1 and 3). However, titratable acidity increased at the 0.25X level and decreased at the 1X level (Expt. 3). In Expt. 2, but not in Expt. 3, citrate concentration in the fifth leaf from the apex of young vegetative plants was correlated with subsequent fruit quality. Three additional experiments in static hydroponics with vegetative plants showed no significant differences in leaf citrate levels due to a single, short-term salt-shock. Thus, citrate is not a good predictor of fruit quality.

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The effect of CO2 concentration (330 and 675 μL·L−1) and photosynthetic photon flux (PPF) (mean daily peaks of 550–1400 μmol·m−2·s−1) on total mineral contents in shoots was studied in chrysanthemum [Dendranthema ×grandiflorum (Ramat) Kitam ‘Fiesta’] during three times of the year. Growth (as measured by shoot dry weight) and shoot mineral contents (weight of nutrient per shoot) of hydroponically grown plants were analyzed after 5 weeks. There was a positive synergistic interaction of CO2 concentration and PPF on growth with the greatest growth at high PPF (1400 μmol·m−2·s−1) with high CO2 (675 μL·L−1). When growth was not used as a covariate in the statistical model, both CO2 concentration and PPF significantly affected the content of all eight nutrients. However, after growth was included as a covariate in the model, nutrients were classified into three categories based on whether CO2 concentration and PPF level were needed in addition to growth to predict shoot nutrient content. Neither CO2 concentration nor PPF level was needed for Mg, Fe, and Mn contents, whereas PPF level was needed for N, P, K, and Ca contents, and both CO2 concentration and PPF level were required for B content.

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In this study, we conducted an economic analysis of high tunnel and open-field production systems of heirloom tomato (Solanum lycopersicum) based on a two-year study at the Center for Environmental Farming Systems (CEFS) located in Goldsboro, eastern North Carolina. The research site was transitional organic using organically certified inputs and practices on land not yet certified. Production costs and returns were documented in each system and provide a useful decision tool for growers. Climatic conditions varied dramatically in 2007 compared with 2008 and differentially affected total and marketable yields in each system. Profits were higher in the open-field system and the high tunnels in 2007 and 2008, respectively. Sensitivity analysis was conducted using a range of market prices from $1.60/lb to $3.60/lb and a range of fruit marketability levels from 35% to 80%. Both systems were profitable except at the lowest price point and the lowest percent marketability level in high tunnel in 2007. At $2.60/lb, seasonal average sale price reported by growers for this region, and depending on percent marketability levels, the payback period for high tunnels ranged from two to five years. Presented sensitivity tables will enable decision makers to knowledgably estimate economic potential of open-field and high tunnel systems based on expected local prices and fruit quality parameters.

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