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   Eur.J.Hortic.Sci. 83 (5) 280-293 | DOI: 10.17660/eJHS.2018/83.5.2
ISSN 1611-4426 print and 1611-4434 online | © ISHS 2018 | European Journal of Horticultural Science | Original article
Application of soilless culture technologies in the modern greenhouse industry ─ A review

D. Savvas1 and N. Gruda2
1 Department of Crop Science, Laboratory of Vegetable Crops, Agricultural University of Athens, Athens, Greece
2 Department of Horticulture, University of Bonn, Germany

SUMMARY
Soilless culture systems (SCS) are increasingly adopted as a major technological component in the modern greenhouse industry. The core advantage of soilless culture, frequently referenced to as “hydroponics”, is the independence of the crop from the soil which, as a natural medium, is heterogeneous, accommodates pathogens, tends to degrade in monoculture systems, and may be infertile, saline or sodic. The cultivation on horticultural growing media (GM) such as rockwool, perlite, and coconut is worldwide the most frequently used SCS for production of fruit vegetables and cut flowers. Water culture systems such as floating hydroponics, Nutrient Film Technique and aeroponics are mainly used for production of leafy vegetables. Modern, fully automated fertigation heads are used for the preparation and timely supply of nutrient solution (NS), which serves both the nutrition and irrigation of the plants. In soilless culture, the NS that drains out of the root zone can be easily collected and recycled, thereby considerably increasing the water use efficiency and minimizing environmental impacts arising from fertilizer residues. The spread of pathogens via the recycled effluents is a challenge that can be encountered by introducing a suitable system for their disinfection before reusing, based mainly on UV radiation, slow sand or membrane filtration, or a chemical treatment (mainly O3, H2O2 or chlorination). In SCS, the NS composition has to be adapted to the composition of the water used for its preparation, the plant species and even the cultivar, the growth stage, the season of the year and the current climatic conditions, and this is a challenge that can be encountered by using modern information and computer technologies. Last but not least, the frequency of irrigation in GM-grown crops is high due to the limited volume of rooting medium per plant and has to be efficiently controlled. Suitable automation technologies are mostly based on real-time measurement of parameters related either to the greenhouse microclimate (e.g., solar radiation, vapor pressure deficit, air temperature) or to the GM water status (water tension or content).

Keywords closed system, growing media, hydroponics, nutrient solution, substrate, water culture

Significance of this study

What is already known on this subject?

  • Soilless culture is a modern cultivation technology applied mainly in greenhouses which developed rapidly during the last 30–40 years. The major objective of this cultivation technology is the elimination of problems associated with the greenhouse soil, such as soil-borne diseases, poor soil fertility, salinity, etc. These main innovations during the 30–40 years that rendered soilless culture the leading cultivation technology in modern greenhouses include the development of suitable growing media (GM) with optimal physical, hydraulic, and chemical properties, such as rockwool and coir, and the advances in plant nutrition and irrigation via modern fertigation equipment and automation technologies.
What are the new findings?
  • In the last years, the research on soilless culture has mainly focused on automation of nutrient and water supply, particularly in closed systems in which the excess nutrient solution is recycled. Special efforts are in progress in order to develop plant factories based on soilless cultivation technologies. Another aspect under investigation is the complete standardization of the substrate analysis in order to obtain more reliable results that can be comparable on a common basis, and to facilitate their interpretation. The present paper, as a mini-review, provides a concise overview of both standard and new findings in soilless culture based on a detailed literature survey.
What is the expected impact on horticulture?
  • The complete control of nutrition via the nutrient solution in soilless culture systems and the optimal physicochemical environment in the root zone due to the use of GM result in higher yields in comparison to soil-grown greenhouse crops, and improve the product quality, particularly in vegetable crops, such as tomato, melon, and lettuce. Furthermore, the switching over from the soil to a soilless root environment results in decreased application of pesticides and other toxic agrochemicals, which are necessary in soil-grown crops to disinfect the soil and control soil-borne pathogens. Finally, the recycling of the excess nutrient solution that drains off after each watering application may contribute to a considerable reduction of nitrate and phosphate leaching to surface- and groundwater resources.

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E-mail: dsavvas@aua.gr  

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Received: 10 October 2017 | Accepted: 20 February 2018 | Published: 12 November 2018 | Available online: 12 November 2018

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