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Wlodzimierz Bres and Leslie A. Weston

`Buttercrunch', `Grand Rapids', and `Summer Bibb' lettuce (Lactuca sativa L.) seedlings were grown with the nutrient film technique (NIT). The influence of two K concentrations (150 and 225 mg·liter-1) and four solution pH levels (5.0, 5.5, 6.0, and 6.5) on lettuce tipburn was investigated in four experiments. Additionally, the influence of pH on foliar nutrient concentration was examined. Even though tipburn was observed in `Buttercrunch' and `Summer Bibb' lettuce, neither K nor pH level consistently affected tipburn incidence. No tipburn was observed in `Grand Rapids'. Solution pH generally did not affect concentration of total N and NO3-N in lettuce tissue. Increasing the pH increased K concentration and resulted in increased proportions of K compared to Mg or Ca. Although the influence of solution pH on P, Ca, and Mg concentration was significant, nutrient accumulation differences were not reflected in lettuce fresh-weight differences. The influence of K solution concentration and pH on lettuce yield was not significant. Tipburn incidence in NIT-produced lettuce appears to be primarily affected by environmental conditions maintained during greenhouse growth.

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D.G. Mortley, P.A. Loretan, W.A. Hill, C.K. Bonsi, and C.E. Morris

Two sweetpotato [Ipomoea batatas (L.) Lam] genotypes (`Georgia Jet' and the breeding clone TI-155) were grown at 12-, 15-, 18-, and 21-h light/12-, 9-, 6-, 3-h dark cycles, respectively, to evaluate their growth and elemental concentration responses to duration and amount of daily lighting. Vine cuttings (15 cm long) of both genotypes were grown in rectangular nutrient film technique channels for 120 days. Conditions were as follows: photosynthetic photon flux (PPF) mean 427 μmol·m–2·s–1, 28C day/22C night air cycle, and 70% ± 5% relative humidity. The nutrient solution used was a modified half-strength Hoagland's solution. Storage root count per plant and per unit area, yield (in grams per square meters per day), and harvest index increased, while production efficiency (in grams per mole) decreased with increased daily PPF. Stomatal conductance for both genotypes declined with increased daily PPF. Leaves were smallest for both genotypes at the 21-h light period, while storage root yield declined as leaf area index increased. Except for a linear decrease in leaf N and K with increased light period, elemental concentration was not significantly influenced.

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Joshua K. Craver and Kimberly A. Williams

Student learning from producing crops in recirculating culture for a 6-week module in the Fall 2013 course HORT 570 Greenhouse Operations Management at Kansas State University was assessed. The module design followed Kolb’s experiential learning model, with teams of students responsible for production of lettuce (Lactuca sativa ‘Green Oak Leaf’) or basil (Ocimum basilicum ‘Italian Large Leaf’) and chives (Allium schoenoprasum ‘Purly’) crops in either a nutrient film technique (NFT) or in-pot recirculating culture system. Goals were to discern if this class experience would 1) improve student confidence and understanding of not only recirculating solution culture systems, but also general crop nutrient management; and 2) improve higher-order learning (HOL) skills of applying, analyzing, and evaluating information. Student learning was evaluated by administering the same survey, which included questions to evaluate student perception, lower-order learning (LOL), and HOL, at four separate times during the semester: 1) before mentioning plant nutrition, hydroponics, or recirculating solution culture; 2) after plant nutrition lectures but before the experiential module; 3) immediately upon completion of the experiential module; and 4) at the end of the semester. An increase in student confidence related to managing crop production in recirculating solution culture and nutrient management was perceived by students upon completion of the module. A significant increase in LOL occurred after the material was presented during the course lectures with an increase also occurring upon completion of the experiential module. In contrast, HOL did not significantly increase after the lecture material was presented, but significantly increased upon completion of the module. Both LOL and HOL was retained at the end of the semester. This evidence supports the role of experiential learning in improving student understanding and fostering HOL.

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D.G. Mortley, P.A. Loretan, W.A. Hill, C.K. Bonsi, C.E. Morris, R. Hall, and D. Sullen

`Georgia Red' peanut (Arachis hypogaea L.) and TU-82-155 sweetpotato [Ipomoea batatas (L.) Lam] were grown in monocultured or intercropped recirculating hydroponic systems in a greenhouse using the nutrient film technique (NFT). The objective was to determine whether growth and subsequent yield would be affected by intercropping. Treatments were sweetpotato monoculture (SP), peanut monoculture (PN), and sweetpotato and peanut grown in separate NFT channels but sharing a common nutrient solution (SP-PN). Greenhouse conditions ranged from 24 to 33 °C, 60% to 90% relative humidity (RH), and photosynthetic photon flux (PPF) of 200 to 1700 μmol·m-2·s-1. Sweetpotato cuttings (15 cm long) and 14-day-old seedlings of peanuts were planted into growth channels (0.15 × 0.15 × 1.2 m). Plants were spaced 25 cm apart within and 25 cm apart between growing channels. A modified half-Hoagland solution with a 1 N : 2.4 K ratio was used. Solution pH was maintained between 5.5 and 6.0 for treatments involving SP and 6.4 and 6.7 for PN. Electrical conductivity (EC) ranged between 1100 and 1200 μS·cm-1. The number of storage roots per sweetpotato plant was similar for both SP and SP-PN. Storage root fresh and dry mass were 29% and 36% greater, respectively, for plants in the SP-PN treatment than for plants in the SP treatment. The percent dry mass of the storage roots, dry mass of fibrous and pencil roots, and the length-to-diameter ratio of storage roots were similar for SP and SP-PN sweetpotato plants. Likewise, foliage fresh and dry mass and harvest index were not significantly influenced by treatment. Total dry mass was 37% greater for PN than for SP-PN peanut plants, and pod dry mass was 82% higher. Mature and total seed dry mass and fibrous root dry mass were significantly greater for PN than for SP-PN plants. Harvest index (HI) was similar for both treatments. Root length tended to be lower for seedlings grown in the nutrient solution from the SP-PN treatment.

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Kellie J. Walters and Christopher J. Currey

Systems LTD., Surrey, BC, Canada). Table 1. Average (mean ± sd ) daily light integral (DLI) and air temperature for hydroponic basil grown in nutrient-film technique hydroponic systems with a range of nutrient solution electrical conductivities (ECs; 0

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Richard V. Tyson, Danielle D. Treadwell, and Eric H. Simonne

keep the recirculating water clean has been well documented ( Adler et al., 1996 , 2000 ; Lin et al., 2002 ). The most common aquaponic systems currently in use employ either a media-filled raised bed, nutrient film technique, or a floating raft

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Alexander Miller, Petrus Langenhoven, and Krishna Nemali

between nutrient solution temperature [heated (18.8 °C) and unheated (13.2 °C)] and production system (CFT = constant flood table, NFT = nutrient film technique) on lettuce shoot dry weight (SDW). Bars and error bars represent interactive least square

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Desire Djidonou and Daniel I. Leskovar

thermal time of 134 °Cd. Fig. 2. Total dry weight of lettuce cvs. Buttercrunch, Dragoon, and Sparx grown in nutrient film technique hydroponic culture at six N concentrations (100, 150, 200, 250, 300, and 400 mg·L −1 ) as a function of the cumulative

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C.L. Mackowiak, R.M. Wheeler, G.W. Stutte, N.C. Yorio, and L.M. Ruffe

Peanut (Arachis hypogaea L.) plants were grown hydroponically, using continuously recirculating nutrient solution. Two culture tray designs were tested; one tray design used only nutrient solution, while the other used a sphagnum-filled pod development compartment just beneath the cover and above the nutrient solution. Both trays were fitted with slotted covers to allow developing gynophores to reach the root zone. Peanut seed yields averaged 350 g·m-2 dry mass, regardless of tray design, suggesting that substrate is not required for hydroponic peanut production.

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R.I. Wilkinson and B. Hanger

Miniature flowering potted Hydrangea macrophylla Thunb. cv. Merritt's Supreme plants (multistem, 15 to 20 cm tall) were grown in a modified hydroponic system. High-quality plants were produced by pulsing plants with paclobutrazol (0.2 mg·liter-1) for 4 weeks. Flower initiation was advanced in the terminal buds of treated plants by 12 days, and this earlier flower development was maintained through to flower maturity, without loss of inflorescence diameter. Chemical name used: β -[(4-chlorophenyl) methyl] -α-(1,1-dimethylethyl)-1 H -1,2,4-triazole-1-ethanol (paclobutrazol, ICI-PP333).