Q & A format. An edited extract from my Aquaponics Discussion Forum where very experienced Aquaponics and regular gardening practitioners contribute.
Here's a question that gets asked of me privately by a lot of Permaculture people of Aquaponics. "Are all the nutrients that are needed by the plants grown in Aquaponics available to it?"
The idea is that an "organic" dirt garden has a plethora of nutrients available to the plant at any moment. The perception is that there are few if little available to the plants grown in an Aquaponics system. This question is raised continually by people who are a little suspicious of things grown in tubs and out of their soil environment and I saw this question raised again today on one of Murray's YouTube video clip responses.
The reader asks politely,
"I am all for organic and chemical free but when it comes to Aquaponics, do the plants receive *all* the nutrients they really need? Soils have an enormous number of elements to them. Despite the artificially created tastes made by the advertisers, variation is a good thing - especially if you are allowing the plants to take up as wide a variety of nutrients as possible. The plants know what they need the best in any given environment. Does anyone know if Aquaponics accounts for this?"
In AP systems I add sea salt and Seasol (seaweed extract) so there are more trace elements than most soils. And with worms mineralising waste in the GB's, in greater numbers than soil. And the plants growing faster and looking and tasting better, my guess is if we are missing something its probably not needed any way.
I regularly make and add compost tea to my Aquaponics systems. It is my firm belief that in order to be an effective gardener of any sort, to have nutrient dense vegetables one must become a master composter.
I think the idea that a dirt garden "has a plethora of nutrients available to the plant at any moment".... is both a fundamental fallacy... and at the same time... an answer to the question...
Dirt gardens have a periodic... and unregulated "flood & drain" regime... i.e rain... and as such, most of the nutrients needed, which are water soluble and motile.... are often unavailable... unless a watering regime is in place...
Similarly, the whole concept of "companion planting"... besides disease/pest considerations... is based upon the understanding that certain plants have different nutrient needs... and that one plant might deplete the needs of another etc...
Then there's the whole "fertilising"... and crop rotation philosophies.... to replenish and provide the necessary trace elements/nutrients so that a plant nutrient and trace element needs are available at all times.
In aquaponics.... we meet all the nutrient needs... of all the plants.... all the time.... within limits of pH lockout of things like iron...
We could go on for hours about this I am sure, but I feel it has been mostly answered in the two previous posts. (above)
How could comparison scientific trials be done ? It would be difficult. An AP garden would be very consistent whereas the best dirt garden would experience a lot of variation in nutrient availability over time.
Gardening of any sort is almost a religious experience....people develop a strong belief that their particular gardening method is the best. Maybe that is not such a bad thing, but strongly held belief systems (paradigms) can sometimes limit logical thought.
I have been asked the same question as Frank outlines, every single time I have presented AP at a Permaculture gathering.
I find that once these people understand just how AP works, particularly a closed loop model such as most of us practice ....flood and drain with worms etc....these folk quickly understand and become just a little excited at the possibilities that a AP system inclusion will bring to their Permaculture vision.
AP inclusion will bring even more balance to an overall food production system, as will the inclusion of wicking beds and so on.
There are a couple of mental barriers to AP, in the minds of Permaculture type purists.
One is the soil....you must have soil with worms and compost to have a proper garden. (we have heaps of worms in gravel grow beds doing what worms do)
Two is the fish food....commercial pellets are made from by-catch and the making and using of them is destroying the ocean fisheries, which is seen as ecological vandalism and unsustainable. (this problem will be solved and there are some very exciting developments as of now 2014. Re sustainable fish food.)
I believe these barriers can be and are being dealt with very effectively and we will see a gradual shift in attitude, and AP will be seen as a very viable and even necessary part of a Permaculture plan/garden...
The name aquaponics can be deceiving. The hydroponics portion of the name implies growing solely in water but in a way, aquaponics grows in water and soil. Dust from the air and other sources will find it's way into the GB. Fish waste will break down into an organic fertilizer that together with the dust and dirt will create an organic soil in the GB. With a regulated flood and drain cycle the plants will also have all the water and air they need, without the loss of water one would expect from a soil garden.
As far as by catch goes, or to be more accurate, fish waste from fish processing such as the heads, gut and skeleton, it's better we use it or else it goes into a landfill.
I believe that the presence of composting worms in AP system grow beds provide the completion of the nutrient question. I have worm feeding stations fitted to most of my grow beds now. Veggie scraps and other compostable material is added to these regularly to provide even more diversity of nutrient source to the AP system. The exciting thing is that in an AP system the nutrients do not get leached away as does happen in a regular dirt garden. The nutrients and minerals are retained in the AP system and evenly distributed.
Let's remember that there is a myriad of bacteria and microbes at work in a mature AP system breaking down and processing material to create a marvellous natural system that is by its very nature, organic.