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Alejandro R. Puerta, Suguru Sato, Yutaka Shinohara, and Toru Maruo

Nutrient film technique (NFT) is the most widespread method of growing plants in a continuously recirculating nutrient solution system ( Saavas, 2002 ). Recirculation of nutrient solution has two beneficial aspects: 1) it reduces the emission of

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

As part of NASA's effort with bioregenerative life support systems, the growth of candidate crops is being investigated in controlled environments. Peanut (Arachis hypogaea L.) was selected for the high oil and protein content of its seed. Peanut cvs. Pronto and Early Bunch were grown from seed, using recirculating nutrient film technique (NFT) in 6-cm-deep, trapazoidal culture trays. The trays were fitted with slotted covers, which allowed developing pegs to reach the root zone. Use of a separate moss-filled pegging compartment above the root zone (tray within a tray) had little effect on seed yield, but resulted in a 60% increase in the nitric acid requirements for pH control. Yields from both cultivars were equivalent to field values on an area basis; however, harvest indices were lower than field values due to the luxuriant canopy growth under controlled environment conditions. Proximate analysis of seeds was similar to field values, with the exception of fat, which was ≈15% lower, and ash, which was ≈30% greater under controlled environment conditions, regardless of cultivar.

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Uttara Samarakoon, Jack Palmer, Peter Ling, and James Altland

nutrient uptake of Lactuca sativa L. grown using nutrient film technique (NFT) Acta Hort. 1266 137 144 Samarakoon, U.C. Weerasinghe, P.A. Weerakkody, W.A.P. 2006 Effect of electrical conductivity (EC) of the nutrient solution on nutrient uptake, growth

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Desmond Mortley, Conrad Bonsi, Philip Loretan, Walter Hill, and Carlton Morris

Greenhouse experiments were conducted to evaluate the effects of spacing within and between growth channels on the yield of `TI-1551 sweet potatoes grown hydroponically using the nutrient film technique (NFT). Spacings within channels were 12.7, 17.8 and 25.4 cm whereas between growth channels the spacings were 12.7, 25.4 and 38.1 cm. Vine cuttings (15 cm) placed in each channel (0.15×0.15×1.2 m) were supplied with a modified half-Hoagland solution and grown for 120 days. Storage root number, fresh and dry weights and foliage fresh and dry weights tended to increase as spacing between channels increased. Spacing of plants within channels had no significant effect on any sweet potato growth responses.

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Yun-Jeong Lee and Eckhard George

A nutrient film technique (NFT) culture system was developed to allow nursery production of arbuscular mycorrhizal horticultural crops. This would benefit horticultural production and allow for uncomplicated production of mycorrhizal hyphae. Roots of lettuce (Lactuca sativa var. capitata) plants were highly colonized by the arbuscular mycorrhizal fungus, Glomus mosseae (BEG 107) after 4 weeks in the NFT system, following an initial phase of five weeks in inoculated in Perlite substrate. In the NFT system, a thin layer of glass beads was used to provide solid support for plant and fungus growth and nutrient solution was supplied intermittently (15 min, six times per day). A modified nutrient solution (80 μm P) was used and was replaced with fresh solution every 3 days. A significantly higher dry weight was found for the mycorrhizal versus the nonmycorrhizal lettuce plants in Perlite during the precolonization period. The root colonization rate was also high at rates up to 80 μm P supply. On the NFT system, growth differences between mycorrhizal and nonmycorrhizal plants were less than in Perlite. However, root colonization rate was not reduced during the NFT culture period. In this system, high amounts of fungal biomass were produced. This would allow the determination of metal and other nutrient concentrations in fungal hyphae. Furthermore, we found large amounts of external fungal hyphae surrounding the root surface. As much as 130 mg fungal biomass were collected per culture plate (three plants). Therefore, we suggest that this modified NFT culture system would be suitable for fungal biomass production on a large scale with a view to additional aeration by intermittent nutrient supply, optimum P supply, and a use of glass beads as support materials. Furthermore, bulk inoculum composition with a mixture of spores, colonized roots, and hyphae grown in soilless media by the modified NFT system might be a useful way to mass-produce mycorrhizal crops and inoculum for commercial horticultural purposes.

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Desmond Mortley, Conrad Bonsi, Philip Loretan, Walter Hill, and Edwin Martinez

Hydroponic experiments using the nutrient film technique (NFT) were conducted in environmental growth chambers to evaluate the response of two sweet potato cultivars, `Georgia Jet' and `TI-155', to two photoperiod and temperature regimes. Vine cuttings of these cultivars were planted in growth channels supplied with modified half-Hoagland nutrient solution using NFT. Plants were subjected to a 24 h photoperiod or a 12:12 h light:dark photoperiod, a constant temperature of 28C or light:dark temperature of 28/22C. Plants were exposed to irradiance levels of 400 umol m-2 s-1 at canopy level and 70% RH. Storage root fresh and dry weights were increased for both cultivars under the 24 h photoperiod at the 28C constant temperature. `Georgia Jet' storage root numbers were not affected by any treatment while those for `TI-155' were reduced under continuous light for both temperature regimes. Foliage fresh and dry weights were not affected by any treatment.

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Roberto López-Pozos, Gabino Alberto Martínez-Gutiérrez, Rafael Pérez-Pacheco, and Miguel Urrestarazu

warm climates, where the NS can easily reach temperatures up to 25 °C, the nutrient film technique (NFT) is negatively impacted. Researchers have tested NFT channel slopes of 0.5%, 1.0%, 2.0%, and 4% and observed the best growth for the 2% slope

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A.P. Papadopoulos and S. Pararajasingham

In growing greenhouse tomato (Lycopersicon esculentum Mill.) using the nutrient film technique (NFT), HNO3 or H3PO4 is usually added to offset the increase in pH of the recirculating solution. For economic and environmental reasons, HCl would be a possible substitute for either HNO3 or H3PO4. Therefore, experiments were initiated to evaluate HCl as an alternative acid in controlling the pH of the recirculating solution in NFT-grown greenhouse tomato. The effects of HNO3, H3PO4, and HCl on the growth, fruit yield, and fruit quality were quantified. In 1995, these effects were tested using `Trust' and `BST 7804' at a recirculating solution pH of 5.5, 6.0, or 6.5; in 1996, only `Trust' was grown at a recirculating solution pH of 6.2. In the 1995 experiment, genotypic differences in marketable fruit yield tended to be smaller when HCl was used to control the recirculating solution pH at 6.0 than when either H3PO4 or HNO3 was used. In `Trust', at a pH of 5.5 under the HCl treatment, fruit quality tended to be higher than in other treatment combinations. In 1996, over a 45-day period, the concentration of Cl that accumulated in the recirculating solution from added HCl was 313 mg·L−1 (313 ppm). There were no significant effects of the treatments on the growth, fruit quality, or yield of the crop. The total marketable yield was better when HCl had been used, likely due to high fruit production at the early part of the harvesting period. Potential savings for the season can be achieved if HCl is substituted for H3PO4 to regulate the nutrient solution pH in NFT-based greenhouse tomato production.

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Edwin Martinez, Conrad Bonsi, Phili p Loretan, Walter Hill, Desmond Mortley, and Carlton Morris

Sweet potato, selected as a potential food source for future long-term manned space missions, is being evaluated for NASA's Controlled Ecological Life Support Systems (CELSS) program. Greenhouse experiments were conducted to determine the effects of two pH treatments on the growth and storage root yield of `T1-155' and `Georgia Jet ' sweet potato cultivars. Vine cuttings of these cultivars were grown in a specially designed Tuskegee University NFT system. Plants were subjected to a continuous pH treatment in which the nutrient solution pH was maintained at 5.00 ± 0.10 throughout the growth period, and a periodic pH treatment in which the nutrient solution pH was adjusted to 6.00 at biweekly changeover intervals and when reservoirs were refilled with deionized water between biweekly changeovers. Results showed that for both cultivars the treatment with periodic pH adjustment had significantly higher storage root yield than treatment with continuous pH adjustment. This experiment is being repeated.

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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