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Introduction to hydroponics
The principles of hydroponics Hydroponics is a method for growing crops without the use of soil, and with nutrients added to the irrigation water (so called fertigation) (Figure 1). The main differences between traditional in-ground growing techniques and soil-less techniques concern the relative use of water and fertilizer, and overall productivity. Soil-less agriculture is also typically less labour-intensive, supports monocultures better than in-ground agriculture, and can be used on non-arable land (Somerville et al.
· Aqu@teachIntroduction to aquaponic technology
Today, as a result of rapid population growth, increased food requirements and urbanization, the amount of agricultural land is rapidly declining and our oceans are overfished. To meet future demands for food, there is a need for innovative, space-saving, and ecological food production technologies. Aquaponics is a polyculture (integrated multi-trophic production system) consisting of two technologies: aquaculture (a fish farm) and soil-less (hydroponic) cultivation of vegetables. The primary goal of aquaponics is to reuse the nutrients contained in fish feed and fish faeces in order to grow crops (Graber & Junge 2009; Lennard & Leonard 2004; Lennard & Leonard 2006; Rakocy et al.
· Aqu@teachIntroduction to aquaculture
Aquaculture is the captive rearing and production of fish and other aquatic animal and plant species under controlled conditions (Somerville et al. 2014). Due to overfishing and the consequent decline of wild fish stocks, aquaculture has become increasingly important in the past few decades (Figure 1), and may become even more so in the future as wild fish stocks face immense pressure from climate change (Gibbens 2019). Figure 2: In 2016 aquaculture accounted for around 47% of total global fish production (FAO 2018)
· Aqu@teachIntroduction
More than 150 different vegetables, herbs, and flowers have been grown successfully in aquaponic systems. Plants suited to aquaponic systems are typically fast growing, have shallow root systems, and a low nutrient demand, such as leafy greens and herbs. Fruiting vegetables, such as tomatoes, cucumbers and peppers, also do well but they have higher nutrient demands and are more appropriate for established systems with adequate fish stocks. But there are some plants that don’t grow well, some that don’t make sense in terms of economics, and some that probably won’t work well due to space restrictions.
· Aqu@teachImportant parameters in aquaponics
In addition to monitoring the general physico-chemical parameters that are important for maintaining water quality in aquaponic systems, and the biological parameters that indicate the system’s performance and reveal potential problems with water quality, it is also necessary to carry out regular check ups on the performance of the technology (filters, water, air pumps, etc.). Technology Solids removal OPERATING PROCEDURE: A major consideration in aquaponics is the retention time and the removal of large particulate matter.
· Aqu@teachHydroponic systems
There are three main types of hydroponic systems (see also Module 1). In media bed hydroponics the plants grow in a substrate. In nutrient film technique (NFT) systems the plants grow with their roots in wide pipes supplied with a trickle of water. In deep water culture (DWC) or floating raft systems the plants are suspended above a tank of water using a floating raft. Each type has its advantages and disadvantages which are discussed in more detail below.
· Aqu@teachHistory of aquaponics
The concept of using fish excrement to fertilize plants has existed for millennia, with early civilizations in both Asia and South America using this method. The most well-known examples are the ‘stationary islands’ or Aztec chinampas set up in shallow lakes in central America (1150–1350 BC), and the rice-fish aquaculture system introduced in Asia about 1500 years ago, and still used today. Both the rice-fish aquaculture system and the chinampas were listed by the FAO as Globally Important Agricultural Heritage Systems (Koohafkan & Altieri 2018).
· Aqu@teachHACCP system
Food safety management consisting of prerequisite programmes (GAP and GHP) and upgraded with a HACCP (Hazard analysis and critical control points) system is a roadmap for aquaponic producers for reducing the risks that may jeopardize product safety. A comprehensive HACCP plan describes procedures for all aspects of production and processing. It also provides a structure for assessing an operation, and serves as a reference for workers during training. Because a HACCP system always has to be adapted to each individual set-up, a generic approach is presented in Table 4.
· Aqu@teachGrowing towers
Growing towers are vertical tubes through which nutrient-rich water is diffused from the top, usually through a drip emitter, thereby creating ‘rain’ inside the tower as it drips over the plant roots that are suspended in the air. The towers, or columns, may either be hollow or filled with a substrate that provides support for the roots and aids in water dispersal. In its simplest form, a growing tower may be a section of PVC pipe with holes cut into the sides.
· Aqu@teachGreenhouse control systems
Control systems include those for lighting, heating, cooling, relative humidity, and carbon dioxide enrichment. Whilst it is helpful to have a fully controlled environment, aquaponic cultivation can also thrive without it, or with only some of the parameters being controlled. Light Maximum light transmission, of the appropriate quantity and quality (PAR, 400-700 nm), is crucial for optimal photosynthesis, growth and yield. If there is too much light in the summer, shade paint or white wash can be sprayed on the outside of the greenhouse.
· Aqu@teach