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Yaser Hassan Dewir, Abdullah Alsadon, Abdullah Ibrahim, and Mohammed El-Mahrouk

that their growth was significantly reduced in a soilless culture compared with culturing in soil. Previous studies offered explanations of this phenomenon, including mechanical resistance that impedes root growth ( Zobel, 1991 ), presence of light

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Charis-Konstantina Kontopoulou, Sofia Giagkou, Efthalia Stathi, Dimitrios Savvas, and Pietro P.M. Iannetta

. van Os, E. Bonants, P.J.M. 2008 Pathogen detection and management strategies in soilless plant growing systems, p. 425–457. In: Raviv, M. and H.J. Lieth (eds.). Soilless culture: Theory and practice. Elsevier, Amsterdam, The Netherlands Raab, T

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Lucina Gómez-Pérez, Luis Alonso Valdez-Aguilar, Alberto Sandoval-Rangel, Adalberto Benavides-Mendoza, Rosalinda Mendoza-Villarreal, and Ana María Castillo-González

suspension Plant Cell Physiol. 41 1286 1292 Pissaloux, A. Morard, P. Bertoni, G. 1995 Alkalinity–bicarbonate–calcium effects on iron chlorosis in white lupine in soilless culture Developments Plant Soil Sci. 59 127 133 Reddy, V.S. Reddy, A.S.N. 2004

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Victor M. Gallegos-Cedillo, Juan E. Álvaro, Th. Capatos, T. Luan Hachmann, Gilda Carrasco, and Miguel Urrestarazu

optimal EC of the nutrient solution for the cultivation of blueberries in soilless culture has not yet been determined ( Voogt et al., 2014 ). Adequate management of mineral nutrition and fertigation parameters in crops ensures good growth and high

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George Gizas, Ioannis Tsirogiannis, Maria Bakea, Nikolaos Mantzos, and Dimitrios Savvas

of productive plants in greenhouses. Hence, the conventionally defined WC and AC do not provide a reliable estimation of the actual water and actual air content at CC in containerized substrates used for soilless culture. The lowest values for both

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Constantinos Tzerakis, Dimitrios Savvas, Nick Sigrimis, and Georgios Mavrogiannopoulos

culture J. Plant Nutr. 28 431 445 Castilla, N. Montero, J.I. 2008 Environmental control and crop production in Mediterranean greenhouses Acta Hort. 797 25 36 De Kreij, C. Voogt, W. Baas, R. 1999 Nutrient solutions and water quality for soilless cultures

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Giancarlo Fascella and Giovanvito Zizzo

. Monthly productive trend of the two Euphorbia × lomi hybrids on soilless culture with two organic media (Year 2005; Expt. 1). z 1 coir dust:1 perlite (by volume); y 2 sphagnum peat:1 perlite (by volume). Vertical bars indicate ± SE of means. A higher

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Jonathan M. Frantz, Cary A. Mitchell, and Jay Frick

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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D. Savvas, H.C. Passam, C. Olympios, E. Nasi, E. Moustaka, N. Mantzos, and P. Barouchas

Two successive lettuce crops were grown in spring 2005 in a completely closed hydroponic system. The ratio of ammonium to total nitrogen (Nr ) in the fresh nutrient solution (FNS) introduced into the closed system to compensate for plant uptake was 0, 0.1, 0.2 and 0.3 on a molar basis. In all Nr treatments, the concentrations of total N, K, Ca, Mg, P, and micronutrients in the FNS were identical, but that of SO4 2– increased as Nr increased, to compensate electrochemically for the enhanced NH4 + and decreased NO3 supply. The highest fresh and dry weights per plant were attained with the highest ammonium supply (Nr = 0.3) but, even when no NH4 + was included in the FNS as an N source, the plants were healthy without apparent nutritional disorders. The ammonium concentration in the drainage solution dropped to nearly zero in all treatments some days after the initiation of recycling, which implies a preferential uptake of NH4-N over NO3-N. The root zone pH, as indicated by the values measured in the drainage solution, decreased slightly as Nr increased, and ranged from 6.5 to 8.0 in all treatments. The leaf K, Ca, Mg, and Fe concentrations were not influenced, whereas those of P, Mn, Zn, and Cu were enhanced by the increasing NH4 + supply. The increased ammonium supply did not enhance the utilization of N in plant metabolism, although it reduced the nitrate concentration of the internal leaves in the early spring experiment. The leaf micronutrient concentrations were clearly more than critical levels even when NO3 was the sole N source for lettuce, whereas the P concentration approached the lowest critical level when Nr was 0 or 0.1. The stimulation of lettuce growth as Nr was increased to 0.3 may be a consequence of enhanced P uptake resulting from better control of pH in the root zone.

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F.M. del Amor, V. Martinez, and A. Cerdá

In order to simulate the usage of brackish irrigation water in greenhouse tomato (Lycopersicum esculentum Mill. cv. Daniela) culture in perlite, plants were supplied with nutrient solutions containing 0, 20, 40, and 60 mm NaCl. The three highest salinity treatments were applied at three different plant growth stages, during early vegetative growth [16 days after transplanting, (DAT)], beginning of flowering (36 DAT), and starting fruit development (66 DAT). Salt tolerance of tomato plants increased when the application of salinity was delayed. Salinity significantly decreased size and number of marketable fruits, but increased fruit quality by increasing total soluble solids and sugar content. Leaf and fruit calcium and potassium concentrations were decreased significantly by increasing salinity levels. This was compensated for the accumulation of sodium. Anion accumulation was increased by increasing chloride concentration. These results indicate that it is feasible to use brackish water for growing tomato with minimum yield losses if salt concentration and duration of exposure are carefully monitored.