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The potential of the sweet potato as a food source for future long-term manned space missions is being evaluated for the National Aeronautics and Space Administration's (NASA) Controlled Ecological Life Support System (CELSS) Program. Several experiments have shown that the sweet potato can be grown hydroponically. However, an evaluation of the NASA fan-shaped Biomass Production Chamber (BPC) channel was initiated to determine if channel depths influenced the yield of hydroponically grownsweet potatoes. Three channel depths were studied, 5 cm (2 in) standard NASA BPC channel, 10 cm (4 in) channel and 15 cm (6 in) channel. The experiment consisted of one replication. The results show that channel depth does effect the yield of storage roots. The 15 cm depth channel provided the most consistent yield with all channels having significantly different fresh storage root yields in the replicate.

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A method was developed to improve the yield and quality of chicons of witloof chicory (Cichorium intybus L.) forced hydroponically from roots taken following long-term storage. The method combines the use of a resilient material (polyurethane foam) with the application of pressure to the developing chicons. At the start of forcing, weights of 0, 150, 300, 450, and 900 g/root were applied to the crown and maintained until harvest. Marketable yields and density of chicons of the late-forcing cultivar Faro increased with increasing weight applied. Increasing weight also significantly decreased the length: diameter ratio of chicons, an indicator of quality. Increased marketable yield and improved quality of `Bea' (intermediate to late-forcing cultivar) chicons were achieved with application of 450 g/root. The technique provides a tool for improving economic yields of late-season, hydroponically forced witloof chicory.

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A 100 parts per million solution of potassium silicate was added to the nutrient solution of well established, hydroponically grown `Kardinal' rose plants. No significant effects of silicon were determined on post harvest life of the rose flowers harvested over a 3-month period as compared to flowers harvested from control plants grown without the silicon additive. Silicon additive did have a significant positive effect on the length of harvested stems.

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A solid-matrix-over-liquid (hybrid) growth system was developed for direct sowing of small-seeded crop species into hydroponic culture and compared for performance with a standard solid-matrix, capillary-wick hydroponic system. Seeds were sown directly onto a 3-cm (1.2-inch) deep soilless seed bed occupying 0.147 m2 (1.582 ft2) within a tray. The planted seed bed was moistened by wicking up nutrient solution through polyester wicking material from a 7.0-L (6.6-qt) reservoir just below the matrix seed bed. The hybrid system successfully grew dense [435 plants/m2 (40.4 plants/ft2)], uniform canopies of dwarf Brassica napus L. in a controlled-environment growth room. Seed yield using the hybrid system was twice that achieved with the matrix-based system. Both systems eliminated the labor needed to transplant many small seedlings from a separate nurse bed into a standard bulk liquid hydroponic system. Root-zone pH extremes caused by ion uptake and exchange between roots and unrinsed soilless media were avoided for the hybrid system by the short dwell time of roots in the thin matrix before they grew through the matrix and an intervening headspace into the bulk solution below, where pH was easily managed. Once roots grew into the bulk solution, its level was lowered, thereby cutting off further capillary wicking action and drying out the upper medium. Beyond early seedling establishment, water and nutrients were provided to the crop stand only by the bulk nutrient solution. This hybrid hydroponic system serves as a prototype for largerscale soilless growth systems that could be developed for production of smallseeded crops in greenhouses or controlled environments.

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Fertilizer costs and increased awareness of point-source pollution are amplifying the pressures on farming, economics along with public demand for sustainable production methods and organically grown produce. Our research focuses on using effluent from thermophilic anaerobic digestion of poultry litter as an alternative fertilizer. Cucumbers (Cucumis sativus L.) were grown hydroponically using a bato bucket system to evaluate the effects of liquid effluent as a nutrient solution versus a commercial nutrient solution. Seeds of the beit alpha cultivar `Manar' were started in Horticubes and transplanted into buckets containing a perlite/coir media. The effluent fertilizer consisted of effluent diluted to the same ppm nitrogen found in the commercial fertilizer based on ammonium measured in the effluent. Hydroponic solutions were monitored twice a day to maintain a pH of 5.6-6.0. Fruit was harvested three times a week and graded on size and shape. Fruit of each grade were counted, weighed, and recorded. Average fruit weight and fruit number produced was statistically significant between the two fertilizer regimes with the commercial fruit, averaging 84 g compared to 75 g for effluent fruit. The effluent treatment produced a greater percentage of grade 1 fruit (33%) compared to the commercial treatment (26% grade 1 fruit). Thus, 74% of the commercial harvest was grade 2 or cull fruit compared to only 66% of the effluent harvest. Correlating grade with average fruit weight analysis identified statistical differences between treatments for the grade 1 fruit, but not the grade 2 or the culls. While effluent from thermophilic anaerobic digestion shows promise as an alternative hydroponic fertilizer, it is not better than the commercial fertilizer regime.

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Mini or “baby” vegetables have become increasingly popular items for restaurant chefs and retail sales. Squash (Cucurbita pepo) are generally open-field cultivated where climate, insect, and disease pressures create challenging conditions for growers and shippers who produce and market this delicate, immature fruit. In order to overcome these challenges, in Spring 2003 and 2004, 18 squash cultivars, including zucchini, yellow-summer, patty pan/scallop, and cousa types, were grown hydroponically in a passively ventilated greenhouse and compared for yield of “baby”-size fruit. Squash were graded as “baby” when they were less than 4 inches in length for zucchini, yellow-summer, and cousa types and less than 1.5 inches diameter for round and patty pan/scallop types. In both seasons, `Sunburst' (patty pan) produced the greatest number of baby-size fruit per plant, while `Bareket' (green zucchini) produced the least. The zucchini-types produced between 16 and 25 baby-size fruit per plant in 2003. The yellow summer squash-types produced on average 45 baby fruit per plant. The production of the patty pan/scallop types ranged from 50 to 67 baby-size fruit per plant depending on cultivar. The cousa types produced approximately 30 baby-size fruit. Total yields were lower in 2004 due to a shortened season. Squash plants will produce numerous high quality baby-sized fruit when grown hydroponically in a reduced pesticide environment of a greenhouse where they can be harvested, packaged, and distributed to buyers daily. The cultivars Hurricane, Raven, Gold Rush, Goldy, Sunray, Seneca Supreme, Supersett, Butter Scallop, Sunburst, Patty Green Tint, Starship, Magda, and HA-187 could be used for hydroponic baby squash production.

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A simple, capillary, non-circulating hydroponic method is described. Lettuce seedlings are transplanted into 218-mm-long plastic tubes containing 160 ml of growing medium and the bottom 25 mm is submerged into a tank of nutrient solution. No additional fertilization, watering, or monitoring is required from transplanting until harvesting. Although the nutrient solution level may drop below the bottoms of the tubes, the roots continue to take up adequate water and nutrients to sustain growth. This method does not require pumps or electrical power. `Green Ice' leaf lettuce produced 24% more salable yield growing with this method than comparable plants growing in conventional soil culture.

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Abstract

The addition of chlormequat chloride to tomato (Lycopersicon esculentum Mill.) transplants decreased fruit yield, number, and size. Flowering was accelerated both by chlormequat chloride and by transplanting at a more advanced stage of development. By transplanting a more mature plant without chlormequat chloride, yield was increased over the first 3 weeks of harvest. Although it is difficult to manage a “leggy” transplant, typical of flowering hydroponic tomato transplants grown under low light levels and close spacing, increased yield was sufficient to justify this management practice. Chemical name used: 2-chloro-N,N,N-trimethylethanaminium chloride (chlormequat chloride).

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The tomato cultivars Edkawi and UC 82B (Lycopersicon esculentum Mill.) were grown hydroponically in a solution [electrical conductivity (EC) 2.4 dS·m-1] containing 150 mm Na (EC 11.4 dS·m-1), 37 mm of K (EC 14.1 dS·m-1), or 75 mm of K (EC 19.7 dS·m-1). The leaf Na content of `Edkawi' and `UC 82B' reached values of 1717 and 2022 mmol·kg-1 dry weight at EC 19.7 dS·m-1, respectively. The high levels of K in the hydroponic solution reduced the Na concentration in the roots, petioles, and stems, but not in the leaves. Potassium concentrations in the petioles of `Edkawi' and `UC 82 B' reached values of 2655 and 2966 mmol·kg-1 dry weight, respectively. At these elevated ECs, the Ca concentrations in the leaves of `Edkawi' and `UC 82B' were 30% and 40% lower than in the control, respectively. The elevated rates of K improved the fruit: flower ratio of `UC 82B', but the high salinity of the solution reduced yields significantly. Plant fresh weight and root dry weight of `UC 82B' were most affected by high EC levels. The elevated levels of K used in this study did not increase yield, but K ions can adjust to Na uptake.

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Authors: , , , and

Turfgrass, which is widely grown and produces a large amount of biomass, could act as a sink for industrial pollutants in urban and suburban regions. Little research has been conducted regarding heavy metal uptake by turfgrasses. The objective of this study was to evaluate root uptake of lead (Pb) in four turfgrass species. Grasses were grown hydroponically in solutions containing from 0 to 450 mg·L-1 Pb, at either pH 4.5 or 5.5, for 4 or 8 days. A significant quadratic relation existed between Pb accumulation in roots and solution Pb concentration within the tested range. The maximum Pb accumulation in roots of the four species was in the range of 20 mg·g-1 dry root weight. Tall fescue (Festuca arundinacea Schreb.) and Spartina patens survived at 450 mg·L-1 Pb solution without showing obvious damage while centipedegrass [Eremochloa ophiuroides (Munro) Hack.] and buffalograss [Buchlöe dactyloides (Nutt.) Engelm.] deteriorated or died at this concentration. This study showed that turfgrass plants can absorb heavy metals efficiently and tolerate high Pb concentration in hydroponic solutions and thus may have a potential use in environmental remediation as a biological extractor of lead.

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