Hydroponics is a method to grow crops without soil, and as such, these systems are added to aquaculture components to create aquaponics systems. Thus, together with the recirculating aquaculture system (RAS), hydroponic production forms a key part of the aqua-agricultural system of aquaponics. Many different existing hydroponic technologies can be applied when designing aquaponics systems. This depends on the environmental and financial circumstances, the type of crop that is cultivated and the available space. This chapter provides an overview of different hydroponic types, including substrates, nutrients and nutrient solutions, and disinfection methods of the recirculating nutrient solutions.

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ReferaatHydroponic Green Farming Initiative is een project dat in Jordanië is uitgevoerd. Wageningen UR Glastuinbouw heeft de huidige stand van zaken bij telers met substraat geanalyseerd met als doel het productiesysteem te verbeteren en om kennis te verspreiden middels trainingen. Door veel zonlicht heeft Jordanië grote productie mogelijkheden. Daar tegenover staat een gebrek aan (goed) water. Substraatteelt kan een hulpmiddel zijn om water te besparen, hiervoor is echter een hoog kennis niveau nodig. Trainingen zijn gegeven voor groepen (3x) en via discussies met individuele telers. Kleine stappen die te nemen zijn, zijn het verhogen van de ventilatiecapaciteit van bestaande kassen en, zeker in de Highlands, het opvangen van regenwater. Alleen hierdoor is al veel water te besparen. Training aan tuinders en samenwerken van tuinders met elkaar, met overheidsinstanties en toeleveringsbedrijven kan verder verbeterd worden. AbstractHydroponic Green Farming Initiative was executed in Jordan. Wageningen UR Greenhouse Horticulture analysed the present situation at hydroponic farmers with the aim to adapt and to improve where possible and to disseminate results and knowledge to other farmers in training sessions. With large amounts of light the potential yield in protected cultivation is huge. Lack of water might stimulate the use of hydroponics. For this more knowledge is required. Small steps forward can be easily taken by increasing the ventilation rate of traditional tunnels and to collect rainwater to improve the water quality given to the plants (especially in the Highlands) and to save water by using hydroponics. Training of farmers and cooperation between farmers and governmental bodies (research, consultancy) and suppliers are more challenging aspects. The traditional greenhouse single tunnel lacks ventilation capacity, which can be cheaply improved by making a slit of 20 cm after each strip of covering foil. Next steps would be a rolling-up sidewall ventilation with insect netting or a ventilation in the top of the tunnel (butterfly type). ReportinfoIn greenhouse horticulture, a rather poor water quality is used with too much salt and often other harmful elements. As being one of the driest countries in the world there are hardly alternative water sources. However, for changing the traditional growing system in the soil towards hydroponics water quality needs to be improved.First step to get good irrigation water is to harvest rainwater. In Jordan Valley only 250 mm of rain is available on a yearly base, but in the Highlands a substantial amount of 300-600 mm is accessible. Also the use of reverse osmosis water seems to be economical. If a hydroponic growing system is introduced, it can be advised to start with an open system in order to learn all details, after a few years recirculation of used water can be introduced as well. Even in an open system 10-20% water and fertilizers can be saved, while production and quality can be improved. A challenge will be the upgrade of current knowledge of growers. A hyd...

Competition for freshwater resources, and legal restrictions on discharge of agrochemicals (plant protection products and fertilisers) increase pressure on agricultural practice to improve water-use-efficiency of crop production globally. Zero-discharge greenhouse crop production can be an effective solution to both problems. Preliminary results of experiments with cucumber and sweet pepper on stone wool substrate in two greenhouse compartments showed that productivity did not significantly differ in zero-discharge growing compared to standard growing strategies. In this paper we present the final evaluation of the sweet pepper trial (December 2014 -November 2015). In the reference compartment a total amount of 465 m 3 ha -1 y -1 (169.3kg N) was discharged. In the zero-discharge compartment there was no discharge during cropping. The nutrient composition of irrigation and drain water was analysed weekly (compared to two-weekly in reference) and nutrient stock composition was changed accordingly. Drain water was filtered with a flatbed filter (no rinsing water) and upon changes in fertigation, the new fertigation solution was first distributed throughout the entire irrigation system by a circulation pump, before application. An irrigation strategy was developed for the end of the cropping season, aiming to drain substrate slabs and to empty drain tanks as much as possible and reduce the amount of remaining nutrients in the slabs, without compromising productivity. Water-use-efficiency of the zero-liquid discharge strategy was lower than in de reference strategy, due to a more vegetative crop growth.