[permaculture] Natural hydroponics, aquatic foodweb & quality food
toby at patternliteracy.com
Sun Apr 7 14:52:08 EDT 2013
I'm appreciating this thread. I have mixed feelings about hydroponics, like aquaponics and many other tech-heavy forms of food production (which is most of modern ag: How much of your food uses a tractor?) Hydroponics makes sense to me in limited cases, such as where soils are toxic and organic matter, access to land, and the other pieces of "natural" agriculture are limited, and where tech resources are easy to get. Cities, in other words. Hydroponics and such can't be considered regenerative, so I can see why anyone slightly purist would loathe them. But as one strategy for increasing local food production, getting techies on board, and using abundant surplus resources like used plastic pipe, blue barrels, swimming pools, pumps that use fewer watts than one light bulb, and such, they seem like useful transition technologies while we clean up soils and tear up pavement. I would like to see us all growing food in healthy soil, but right now I see growing healthy people via nutrient-rich foods a more important goal than being organo-purists. I don't want to see city people growing food in lead paint chips. The healthier people are, the less I see them watching TV and believing propaganda. Organic doesn't automatically mean healthy.
In (narrow) terms of nutrition, soil is a delivery medium to get minerals into plants. It stores the minerals. Water-based systems don't need storage, they rely on flow. In natural systems, microbes degrade organic matter to get the energy stored in carbon bonds, eat some of the minerals there, and release a lot more minerals into the soil water, where they are adsorbed by clays and humus, and then taken up by plants. In that old refrain of chemical farmers, the plants don't care where the minerals come from (the soil does, the microbes do, and the earth does, though!). But there is very little natural about farming, even when it's done in soil. Broccoli, carrots, corn, and cauliflower are not found in nature. To manage these highly bred cultivars, we need to pump a lot of minerals into them. Soilless culture is a highly effective way to get those minerals into them. I know that a lot of hydro growers overuse nitrogen and get overpumped plants, but that's just poor management and not an intrinsic flaw in the method.
I slightly prefer aquaponics to hydro because it is a microbe-based food system, unlike hydro which is salt-based. But I'm not wild about the fish-in-prison aspect of aquaponics. Both deliver much higher and faster yields than soil systems, and there is a place for that: In energy- and resource-dense environments that are far from good soil.
I'm really starting to shift my viewpoint on organic purism.At our home, organic matter has been trucked in for 30 years--two feet of it overlaying an acre of rocky shale/silt. It's shockingly low in minerals, and the incredibly high CEC (50-80!) means I just have to pour in minerals to get any of them to the plants. Rock dusts will work long term, but to get nutrients now, I'm using lime, gypsum, bone meal, fish and grain meals, plus a bit of calcium nitrate, mono-ammonium phosphate and trace elements. Like Wm Albrecht, Carey Means, Steve Solomon, and Michael Astera, I'm no purist: I want nutrition-dense food now.
People here have said hydro and aqua food seems lifeless to them. Well, I've seen a lot of mediocre food come off of organic farms. Just adding compost and manure, and even rock dusts won't add critical minerals--the essence of healthy food--if they are not present in the composts and dusts. A lot of organic food strikes me as nitrogen heavy. We've badly depleted our soils of minerals (P, K, S, Ca, Mg, Fe, Cu, Bo, etc) through farming, and anywhere the rain is over 25 inches, minerals may have leached beyond roots ability to get them. I think that's why we're seeing research that says there is no health benefit to eating organic. Just as chem farmers have erred in forgetting about organic matter, many organic farmers have forgotten about minerals. Balancing both is key. So if I only have a choice between chemically grown mineral-dense food and manure-pumped organic, as long as neither is sprayed, I might take the chemical route. For now. Until we get all those mineral cycles nicely closed up and looped into our technosphere. When we're all living in closed-loop, fertility-cycling, humanure-using food forests, we can build art out of the hydroponics systems.
Apologies, as usual, for the long rant.
On Apr 6, 2013, at 9:55 PM, venaurafarm wrote:
> On 4/7/2013 12:40 AM, venaurafarm wrote:
>> On 4/7/2013 12:25 AM, Steve Hart wrote:
>>> On the subject of hydroponics I do recall a recent debate raging about
>>> acquaponics which like hydroponics has little to do with
> You participated in that discussion.
>>>>> Which the way I understand hydroponics: There's no soil, no
>>>>> soil-food-web, no soil biology - it's not even agriculture (much less
>>>>> permaculture), which helps explain why I become distempered if I eat
>>>>> even a little (something which I would not knowingly do).
>> There is no soil, there is aquaculture foodweb and biology. Read the
>> thread on this and pay attention to Toby's input. That will explain all.
>> Then Google the subject for more detailed information.
> Here you go:
> Toby Hemenway toby at patternliteracy.com:
> Well-aerated, nutrient-rich water can grow vastly more microbes than any
> soil. I used to run a fermentation lab, so I've done it, easily. This is
> why wetlands are so important--and they work because wetland plants pump
> out oxygen at far higher rates than most terrestrial plants, and
> nutrient diffusion rates in water are far higher than in soil. Plus soil
> is mostly rock or carbon, which displaces bacteria, while water doesn't
> displace them--the sheer density of microbes in water can be far higher.
> The few billion bacteria per gram of healthy soil are a fraction of what
> a healthy wetland or an aquaponics system can achieve.
> Like any system, aquaponics is not appropriate for every situation. But
> in places where land is scarce (cities), conditions are unreliable (many
> places), technical resources are more available than soil, and a number
> of other situations, aquaponics can allow food--and dense protein--to be
> grown where it otherwise can't.
> You can get rid of fungi and other diseases more easily than in soil
> because you can circulate a treatment through the entire system very
> quickly or even replace the water, unlike soil.
> I'm grateful to Kathryn K for staying so level-headed and reasonable in
> the face of some assumptions not well based in fact. I used to have a
> strong prejudice against aquaponics, but it pretty well dissolved after
> I learned more about it. I'm awfully fond of soil-based systems, but
> aquaponics has its advantages in some places. It's a useful tool.
> I, like most people, have a strong preference for working in the dirt
> instead of using a bunch of tanks and pipes to grow food, but, then,
> soil ag, too, is pretty mechanized these days.
> To sum up: there is nothing special about soil, in one sense: it is a
> medium for the propagation of the microbes that convert manure and other
> non-available nutrients into plant-available nutrients, and it can hold
> water and air. Same with water. Instead of a rock-based medium to hold
> microbes and nutrients, aquaponics uses water as the medium, which is a
> nice stacking of functions, if you think about it, because soil has to
> be kept wet for microbes and plants to grow, while water doesn't, and
> most of the nutrients that plants use are water soluble, converted into
> that form from insoluble form by microbes. The carbon, the energy source
> for the microbes, is provided by the OM in the fish manure instead of OM
> from insect frass and animal manure.
> And aquaponics has a couple of advantages over soil systems, because a
> water medium can transport nutrients to microbes and plants much more
> quickly than soil. In soil, water moves by diffusion, and once the
> water, or the nutrients in it, are used up in one area, the organisms
> must wait for more to diffuse in before they can feed or get moisture,
> and that can take time--and sometimes it doesn't happen, and the plants
> or bugs die. Same with oxygen, which can't travel well in compacted soil.
> But in a water medium, nutrients are constantly being circulated to
> where they are needed, as is air. That's one reason that growth rates in
> aquaponics is much faster than in soil.
> To make it clear: Aquaponics is not hydroponics plus fish. Hydroponics
> uses water-soluble nutrients from the get-go, with no microbes in the
> mix. Aquaponics, just like soil ag, relies on microbes to convert manure
> into plant-available form. Big difference--the former is chemistry, the
> latter is an ecosystem.
> One thing to keep in mind about aquaponics is that bacteria and other
> microbes are as critical a part of the system as in soil. The fish
> manure is not some liquid fertilizer that goes straight to the plants.
> It contains N primarily in the form of ammonia, and the usual bacteria
> are present in the gravel beds (which are best made with lava rock or
> some other high-edge substance) to convert it to nitrite and nitrate.
> Many of the nutrient-releasing processes are the same as in soil. As
> long as your fish food comes from a balanced source, a good nutrient
> balance will go to the plants. (I agree that you probably don't want to
> make aquaponics your exclusive vegetable source.)
> People also complain about the embedded energy in these systems, which,
> indeed is higher than the energy footprint of a soil bed. But since most
> farming is done with tractors and other equipment, and chickens live in
> coops made with manufactured materials that have a high energy
> footprint, and we drive to the store to buy our food, etc, etc, I think
> that argument goes away.
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