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Miguel Urrestarazu, Pilar Carolina Mazuela, Abdelaziz Boukhalfa, Antonia Arán, and María del Carmen Salas

Based on a new structure for plastic culture channels, a new system for soilless culture called New Growing Systems (NGS) has been developed. It is similar to the nutrient film technique (NFT) but with several potential advantages. Each NGS growing channel has five plastic layers and a large number of holes, there is a dripper every 0.5 m above the first layer of plastic, and each dripper supplies the nutrient solution which flows from the second layer over the others to the end. Three separate greenhouse experiments with tomato, cucumber, and sweet pepper using NGS channels were conducted in Almería (southeastern Spain). The oxygen content in the circulating nutrient solutions was determined at different points and different times along the channels of all crops. Depletion of oxygen content in the nutrient solution was lower than NFT channels. Oxygen content in NGS showed some advantages compared to NFT.

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Cristian Moya, Eduardo Oyanedel, Gabriela Verdugo, M. Fernanda Flores, Miguel Urrestarazu, and Juan E. Álvaro

, nutrient concentrations are sometimes higher than necessary for optimum plant growth and yield, and there is limited information about the effects of increased EC nutrient solution management in soilless culture. Hence, this work aims to assess the effects

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R.W. Zobel and Laura Matthews

Aeroponics, as a method of soilless culture, has been in intermittent use since the 1950's. Early Russian and Italian research suggested that productivity and use of space was optimized with this technique. Prior to the introduction of ultrasonic techniques, aeroponics utilized spray nozzles or spinning disks. In addition to the need for frequent cleaning, the first results in the formation of a boundary layer on the root surface, similar to that formed in hydroponics, which results in nutrient and aeration gradients. The second results in significant physical disturbance to the root system and, except under very controlled conditions, also develops a boundary layer. Ultrasonic fogs avoid these side effects and allow the use of carbon dioxide enrichment of the root zone as well as reduced nutrient concentrations. Initial results with commercially available equipment are very promising. Commercial implementations of ultrasonic aeroponics promise to be far less energy and manpower intensive than any other method of plant culture. Lettuce, corn, tomato, soybean, dry bean, and geraniums have all been cultured with this method.

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Isidro Morales and Miguel Urrestarazu

, D. 2012 Algunos usos de la visión artificial y su aplicación en la horticultura protegida Vida Rural 343 46 48 Fernández-Bregón, N. Valera, D. Urrestarazu, M. 2013 Uniformity of fertigation as diagnosed by infrared thermography under soilless culture

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Malik G. Al-Ajlouni, Jamal Y. Ayad, and Yahia A. Othman

., 2015 ; Polat et al., 2004 ; Silber and Raviv, 1996 ). Accordingly, using 0 to 4-mm substrate holds promise for improving growth and flower quality of asiatic hybrid lily grown under soilless culture. Units Literature cited Adams, P. 2002 Nutritional

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I. Grafiadellis, K. Mattas, E. Maloupa, I. Tzouramani, and K. Galanopoulos

The financial effectiveness of the soilless culture system (SCS) of gerbera (Gerbera jamesonii Bol. ex Adlam.) production was compared with that of the soil culture system in heated greenhouses in northern Greece. Evaluation was based on budgeting procedures that assumed a project life of 9 years. The decision to accept or to reject the investment was based on the following criteria: 1) net present value analysis (U.S. $18,414), 2) benefit/cost ratio, and 3) risk exposure ratio. The soilless culture system, particularly the plastic bag system using perlite media, was more profitable. Application of sensitivity analysis illustrated the significance of product price and discount rate in determining the accrued benefits.

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Md. Jahedur Rahman, Haruhisa Inden, and Masaaki Kirimura

al., 2004 ; Romero et al., 2004 ; Van Hooijdonk et al., 2004 ). However, there has been little attention paid to application timing of nutrient solution for sweet pepper in soilless culture. Russo (2011) conducted research on irrigation timing in

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K. Mattas, M. Bentes, G. Paroussi, and I. Tzouramani

The financial effectiveness of a soilless vertical bag system of hydroponics culture was evaluated for off-season strawberry (Fragaria ×ananassa Duch) production in heated greenhouses in northern Greece. Financial analysis revealed that the implementation of this soilless culture system instead of the traditional production system under plastic tunnels would not be profitable for Greek farmers due to its high initial investment and high fuel consumption. Sensitivity analysis indicated the importance of product price in affecting the magnitude of benefits, confirming the interest of farmers to produce off-season strawberries to market them when prices are likely to be higher. In addition, yield increase will have a positive effect upon farmers' income.

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M. Raviv, R. Wallach, A. Silber, Sh. Medina, and A. Krasnovsky

Rose (Rosa sp.) plants (`Mercedes') were grown in yellow tuff (YT) (volcanic ash, scoria) and pumice from Italy (PI) and Greece (PG) for which physical and hydraulic characteristics were determined. The differences among the measured retention curves of these materials result in significant differences among their relative hydraulic conductivity functions. The hydraulic conductivity of YT is much higher than that of PI, which is higher than that of PG. The plants were subjected to optimal growth and nutrition conditions. Irrigation was controlled using electronic tensiometers, at suction values well within the range of easily available water: 13 cm for YT and 8 cm for the two pumice types. Nonetheless, yields were significantly higher in YT than in PI; yields were even lower in PG. We suggest that the limiting factor was the dynamic water availability to the plants, which is affected mainly by the unsaturated hydraulic conductivity. The relative hydraulic conductivity of YT at 13 cm is more than an order of magnitude higher than that of PI at 8 cm. The relative hydraulic conductivity of PG at 8 cm is two orders of magnitude lower than that of YT at 13 cm. It seems that the current concept of easily available water, based on a predetermined suction range, independent of the hydraulic characteristics of the media, is not an appropriate parameter for irrigation management in soilless culture. The unsaturated hydraulic conductivity, being a characteristic function of the medium and highly sensitive to moisture variation, indicates better the actual availability of water to the roots. Therefore, it should be used for irrigation control in containers filled with porous substrates.

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Judith Pozo, Juan E. Álvaro, Isidro Morales, Josefa Requena, Tommaso La Malfa, Pilar C. Mazuela, and Miguel Urrestarazu

widely dispersed such as rockwool, perlite, or coconut fiber, which occupy areas of ≈5000 to 5500 ha ( Urrestarazu, 2013 ). Table 1. Variation in some characteristics of pozzolans (volcanic rocks) used in soilless culture systems worldwide. Currently, the