No abstract

A recent study related to aquaponics has shown that hydroponic lettuce grown in aquaculturederived supplemented water grew significantly better than lettuce grown in a conventional hydroponic system. The principal objective of this study was to verify this finding in a larger setup. Even though the aquaculture water that was added to the aquaculture-based hydroponic system contained relatively high amounts of sodium, we were still able to observe an enhanced growth performance of the lettuce in that system compared to the lettuce grown in the conventional hydroponic nutrient solution. The lettuce final fresh weight was 7.9%, and its final dry weight even 33.2% higher than the one of the hydroponic control.

Aquaponics -the co-production of fish and plant products -is gaining interest both by entrepreneurs and researchers. This article evaluates both the technical setup as well as the economic potential of aquaponic systems and is aimed at identifying relevant knowledge questions for further improvements. Using system requirements for hydroponic systems and aquaculture, the aquaponic system was compared to a typical Dutch rockwool system. Aquaponics was found to be an improvement on current practices when using Deep Flow Technique (cultivation in a flowing thick water layer), resulting in better nutrient availability for the plants and re-use of nitrate. However, the technical challenges of the direct linkage between the two production systems in terms of needed technology and disease management was found to make the total system suboptimal when compared to conventional practices. The technological advantages of efficiency in use of land and energy and re-use of nutrients were found to be a marginal cost reduction of 1.2%. The article concludes that the added value of aquaponics can be found in the total business concept of producing in an urban environment with direct relationship with consumers. Further improvement of aquaponics can be found in improved disease management of the system -through management or improved design. INTRODUCTIONUrban farming creates value through the production of small scale, sustainable and local produce, often in direct interaction with the consumer. Sustainability is achieved through the re-use of waste streams of water, nutrients and energy by combining different (agricultural) activities. A sustainable, applicable and small scale system for such re-use is the combination of fish production in Recirculating Aquaculture Systems (RAS) and horticulture -so called Aquaponics. For professional aquaponics to take off in Europe the production systems need to have added value, be robust and easy to use. Research has focused on plant aspects (nutrients and quality; Pantanella et al., 2012) and fish production (densities, diseases) and technology. But less on the business rationale and design structure. However, designing for such complex systems requires a systematic approach, where an analysis of functions and quantified requirements is used to select and improve on the technical lay-out. Functions and requirements are based on insights and needs from both researchers and experts as well as users and stakeholders -in the case of urban farming city planners and the general public. However, such analysis has only recently been developed for both hydroponic systems and aquaculture, but not for the combination of the two nor the application in an urban setting. This paper describes the system requirements for both aquaculture as well as horticulture that would apply for aquaponics in an urban environment.

No abstract

Soilless cultivation suggests a closed system of water flows, of which (drip) irrigation, evaporation andin more high-tech systemscondensation water are the main flows. However, in practice growers discharge water during the process of filter cleaning and actively discharge water due to high levels of sodium or contamination with chemical or biological components. On average in the Dutch greenhouse situation 2-5% of the annual irrigated water is discharged, spread over the year. These discharges lead to pollution of surface water with nutrients as well as (residues of) plant protection products (PPPs). This awareness led in 2008 to the start of a working group that aimed to develop an risk evaluation tool for pesticide authorisation in Europe. The evaluation tool consists of a modelled approach for determining expected concentrations in surface water based on a reference scenario per crop i.e. a description of an actual situation including the technical layout of the glasshouse, the climatological year and the receiving ditch.

No abstract

No abstract

When chrysanthemum growers change soil for a soilless growing system they aim for labour cost reduction, quality and yield improvement and reduced emissions of nutrients. Because many attempts to come up with a viable soilless system failed, improvements and systemizations of the design process were examined. The design methodology chosen uses goal setting based on stakeholder engagement, systemised quantification of a set of conditions for the final system, and a systemised choice of competing systems and quantification of the properties of the competing systems. The set of conditions is assembled upon consultation of a wide variety of growers and experts in fields of plant protection, plant physiology, water management, substrate characteristics, economics and nutrition. The conditions and properties correspond to each other to the extent that both are based on the same measuring methods and expressed in the same units. Thus matches between conditions and properties can be scored. After the complete set of conditions and matching properties is scored, the average of the scores is taken as a measure for the suitability of the whole system. Because properties are quantified, the process is based on knowledge, and gaps in knowledge are identified. Favourable combinations of properties may be applied to systems lacking these properties in order to improve them. This design methodology was used to select and improve a set of 11 competing systems. The resulting 4 improved systems were built and used for growing in experiments. Systems included a soil bed, a sand bed, a peat bed and a cassette bed. The soil bed was a 70 cm deep bed of the original soil on a water impermeable foil with a drainage system. The sand bed was a 15 cm layer of coarse sand with a 5-10 cm under layer of coarse clay pellets including a drainage system which also supplied irrigation water i.e. sub irrigation. The peat bed was a 25 cm peat layer on a sub irrigation bench. The cassette bed was a 130×3×15 cm (length × width × height) container filled with peat. The cassettes were hung on a sub irrigation bench. Chrysanthemum press pot plants were planted on soil and sand beds and bare chrysanthemum cuttings were planted in the peat based systems. Chrysanthemums were grown for the first of 6 crop cycles. Results showed a 5-15% increase in dry matter production and 3-5 days shorter growing period in the peat beds and cassette beds. However, the economic performance is still marginally poor. Nevertheless, the systems tested are environmentally sound and comply with plant requirements for optimal growth. The sand bed and cassette bed may be further optimised by respectively EC control and top down irrigation.