아쿠아포닉 구성요소 2 화단(grow bed)
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2. 화단 (grow bed)
화단 grow bed 는 식물이 자라는 곳을 말한다. 우리말 직역이 어색해, 여기서는편하게 화단으로 통칭하겠다.
화단 깊이는 최소한 30cm는 되어야 식물이 뿌리내리고 살기에 적합하다. 시일이 경과하게되면, 식물의 뿌리가
생각외로 많이 번지게 되어, 벨사이폰 시스템을 막아 물의 순환을 어렵게 하곤한다 아쿠아포닉의 특징이며,장점
이라고 할수있는 밀식을 하게되면 이종식물들간에 뿌리가 엉키곤 하는데. 이는 화단의 깊이가 얕은곳에서 종종
화단에는 흙대신 자갈등 입자가 굵은 고정물을 담게되는데, 이는 물이 잘빠지고, 필터역활을 잘할수있는 것으로
하는것이 좋다.그리고 수조에서 펌프로 올라오는물을 주기적으로 흘러 내리게하는 사이폰시스템이 자리잡는다.
세부적인 내용은 다음순서에 기술하기로 한다.
필자의 각종화단을 소개하면 아래와 같다.
위 사진과 같이 다양한 형태의 화단을 구성할수 있다. 아쿠아포닉의 장점인 협소한 장소, 농지가아닌 사막이나, 흙이
없는 옥상등 농업행위를 할수없는곳에서 농업을 행할수있는 장점이므로 , 그장소에 알맞는 모양을 구성하면된다.
화단 역시도 경제성, 효율성, 디자인등에서 많이 달라 질수가 있다.
쉽게 생각하면, 요즈음 많이 이용하느 수경재배의 화단을 생각하면된다. 아쿠아포닉은 고기양식과수경재배의 결합
이므로, 식물부분은 수경재배의 양액만 빼고, 수경재배와 같다고 생각하면된다.
외국의 화단모양을 몇가지 에시해 보겠다.
위와 같이 각종 아쿠아포닉에 따라 다양한 모습을 가지게된다. 역시 경제성과 효율성을 먼저 감안하는 것이 좋다.
*참고: 아래글은 일본 아쿠아포닉 사이트에서 소개한 화단(grow bed), 일본에서도 아쿠아포닉 활동은 왕성 합니다
잘 정리된 일본 아쿠아포닉 사이트를 소개하면서, 화단(grow bed)부분을 번약해 첨부합니다.
Types of Growing areas used
Aquaponics systems use several common components and the growbed (the hydroponic part of the system) is obviously one of the most crucial. The choice of growbed is also much debated, with newcomers to aquaponics often wondering what they can use, re-purpose, build, scavenge or buy for use in their backyard aquaponics systems. Before looking at some of these choices we should note that there are three main types of growing systems that are usually used:
• DWC or Deep Water Channels, which are long, deep troughs that hold floating rafts
• NFT channels (Nutrient Film Technique) which are usually found in hydroponics set-ups.
• The final type is the media filled growbed, and this is the type that we will concentrate on in this article.
Types of Filtration
An aquaponics media filled growbed is simply a suitable container that is filled with a growing media such as gravel, hydroton or lava rock, and is the most commonly used type of growbed as it neatly performs four separate functions in an aquaponics set-up. Firstly and most obviously it provides support for the plants up and provides somewhere for the roots to take hold. In addition to this, the media provides three separate filtering functions:
• Mechanical Filtration - the media helps to filter the solid waste in the water and to trap it in the bottom of the growbed.
• Mineralization - this is the process whereby the solid waste breaks down and is returned to the water so that the plants can use it.
• Biological filtration - the media provides extensive surface area for the beneficial bacteria to colonise.
As the media filled growbed performs all of these functions in one single place, it is one of the easiest, most space-efficient and also one of the most cost-effective ways to set up a new system. This is of particular concern to newcomers to aquaponics who may not feel comfortable with more complicated filtration systems, or who want the most hassle-free way to start supplementing their diets with fresh, nutritious produce grown via aquaponics.
So what can you use for a growbed?
The short answer is almost anything, but there are a number of things you should take into consideration, including whether your growbed will be located inside or outside. It goes without saying that the growbed needs to be waterproof, but you need to make absolutely certain of this.
It also needs to be strong enough to hold the media and the water - depending on the size of the growbed this could equate to a fairly significant amount of pressure... an important consideration if you decide to make a growbed yourself.
Any watertight, food-safe, fish-safe container can be used, and depending on the size of your whole aquaponics system that will leave you with several choices.
•Small systems can use food containers, plastic containers from the DIY store or IKEA, wooden boxes with a suitable liner - almost anything that will fit the size of your fish tank.
•Medium sized systems can use cut up IBC totes, Rubbermaid-type water troughs, animal feed troughs, concrete mixing troughs and similar things.
•Larger sized systems can use multiple units from above, hand built and lined wooden growbeds, and of course, commercially available aquaponics growbeds.
Aquaponics Growbed Materials
A growbed can be made out of a wide variety of materials but care should be taken to make sure it fulfills certain criteria. A growbed should be safe to use first and foremost, and should be made of a materials that will not leak unwanted chemicals into the water, or that will affect the pH of the water.
A growbed should ideally be made of a material that blocks out the sun, as direct sunlight can promote algae growth and can be detrimental to plant roots. If the growbed is being used outside then it will also need to be UV stabilized to ensure that it will not degrade in the sunlight and leach chemicals into the system.
Commonly used materials would be certain plastics, wood, fibreglass and anything with suitable waterproof liners. Concrete can also be used but care needs to be taken to seal the concrete first as concrete can affect negatively affect the water chemistry of your system
Growbed depth and Size
An aquaponic growbed needs to be the right size to fit your fish tank volume. It needs to be able to provide adequate mechanical filtration and biological filtration for the nutrient-rich water, and so you should always consider the growbed and the fish tank together and use appropriately corresponding sizes.
A common rule of thumb is to use a 1-1 ratio. The growbed volume should be equal to the fish tank volume. This is by no means a hard-and-fast rule but serves as an outline guide.
The plants in your system are also part of your filtration process and so you must ensure that you have adequate surface growing area relative to the same of your fish tank. As a rule of thumb, if 1000 litres of water needs approximately 1 meter cubed of growbed media volume for filtration, then if your growbed is 25cms deep you will need a surface area of approximately 1m x 4m to ensure that there is approximately 1 meter cubed of media volume.
•The surface layer (5cms) - this is above the waterline and should not be wet - this reduces loss of water through evaporation.
•The root layer (20cms) - this is where your roots will be growing and where most plant activity will take place. This is layer is normally regularly flooded and drained.
• The solids layer (5cms) - this is where the solid waste will collect in your system and which will usually be constantly flooded with water.
From these layers we can work out a kind of 'ideal depth' of 30cms or 12 inches. Whilst this depth has been proven to be highly effective it is by no means then only depth that can be used. Aquaponics systems have been shown to work equally well with growbed depths of as little as 10cms or so - but care needs to be taken to always ensure that you have sufficient volume to provide adequate filtration for your system.
At the end of the day, don't feel that you have to use a specific size and type of growbed. As long as it is safe, strong and appropriately sized for the system that you are building, then it will be worth trying out.
If you can build a growbed that is 30cms deep then you can be confident that this is a tried-and-tested depth that has been proven to provide very effective results - but you can also rest assured that a shallower or deeper growbed is also likely to give you good results.
Keep in mind that of the four functions that a growbed traditionally performs, three of those are related to filtration, and so your main consideration when choosing a growbed size, is to ensure that it is able to provide adequate filtration for your own aquaponics system, including adequate planting area.
Don't be afraid to be creative - as long as you can follow the guidelines noted above, then try anything that you have to hand - or anything that you think would look great. Put safety first and you can't really go too far wrong.
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