permenetly flooded grow beds????

[kevclark]

I have a small floating raft grow bed where the roots work their way down to the water and the top half of the plant is dry. I got to thinking, what would happen is we had a gravel grow bed that was constantly flooded with the exception of 2 or 3 inches at the top. The plants could be planted in the dry gravel and be watered by capillary action.

Any Thoughts?

[Yabbies4me]

Hi Kev,

"Constant Flood" has been discussed at length, and comparison tests have been run, here and elsewhere. Some are in favour of it, some aren't. The end results were similar when compared to Flood & Drain using an auto siphon, and Timed F&D systems. It comes down to personal choice and how you want to set your system up.

You should be able to find the posts/threads quite easily using the search function.

Cheers, Yabbies.
.

[lefty]

I am running constant flood
another benefit of constant flood is that it keeps the total water volume higher than flood and drain without the need of a sump.

[Jens UK]

how do the worms like constant flood???

[benwalters]

i assume 'constant flood" and "continuous flow" are the same thing
plant growth may be comparable in these systems
but comparisons i have seen on forum do not measure the ability of the grow bed to host bacteria, and oxygenate water,

continuous flow may have energy benifits though

re. worms, the grow bed is not completelly flooded, and worms can apparentlly handle water if it is oxygen rich

ben

[kevclark]

Thanks folks. I really appreciate the input. I do have a place where I could set up a small grow bed and try it out, so based on your feedback I might give it a shot.

Thanks again.

[MrWright]

i assume 'constant flood" and "continuous flow" are the same thing
My understanding is that they aren't the same.

Constant flood is that the beds are always 'flooded' therefore there is no change in water level in the grow beds (and of course the fish tank/sump etc.) as well as there being no ebb & flow.

Continuous flow is that the pump does not stop running and the grow beds can either be constant flood or use auto-siphons to create the ebb & flow.

[RupertofOZ]

Indeed... and continuous flow is utilised in DWC raft systems.... or even NFT...

Constant flood... is a continuous flow method... but it signifies a level of flood.. as opposed to flood & drain, ebb & flow...

[benwalters]

so a constant flood situation needs a fair bit of flow to keep water from becoming stagnant,

the point i was trying to make before ,is that plant growth in a "ebb and flow" vs "constant height" gravel growbed may be more or less equal,

but ebb and flow could have advantages with regard to fish growth via increased oxygen input into water and better nutrient conversion in growbed therefore cleaner water?

cheers ben

[RupertofOZ]

Instinctively I would have thought that would be the case Ben... but the trials done at BYAP, and those Murray have done... tend to suggest that our AP systems are oxygenated well enough for both plant growth and nitrification...

As an aside... ebb & flow and flood & drain... aren't necessarily the same thing...

Ebb & flow... as sometimes applied in some hydroponics... often fills the container/media from bottom up...

Flood & drain almost always floods from top down...

[MrWright]

so a constant flood situation needs a fair bit of flow to keep water from becoming stagnant,
Not necessarily. Water is fed on the top of the grow bed (as per most set-ups) and the water is drawn from the bottom of the bed via the holes in the gravel guard and out via the standpipe. Having a higher rate of flow means that the water in the grow bed will recycle more often, but you also need to consider how oxygenated the water going in is.


the point i was trying to make before ,is that plant growth in a "ebb and flow" vs "constant height" gravel growbed may be more or less equal,
The jury is still out on that one. It almost depends on who is doing the testing... ;)


but ebb and flow could have advantages with regard to fish growth via increased oxygen input into water and better nutrient conversion in growbed therefore cleaner water?
Again, not necessarily.

[Murray]

The only thing we have ever observed is the development of tracking in the grow bed over time and because of that anaerobic areas developing and in some cases actual dry areas.
Also, to ensure good distribution of the water it is good to build a distribution grid around the outside perimeter of the bed on top of or just below the surface of the gravel/clay pebbles. This has holes drilled in it about 200mm apart and around 6mm in size. This sometimes needs maintenance as the small holes tend to block with algae and so on.

[benwalters]

Mr Wright,
i have water pumps that operate bell siphon and looped siphon in 2 setups, both have fish tank below growbeds (non-CHOP)

im interested in methods that reduce the energy used to move this water

a constant height, (constant flood) gravel growbed would require less flow , because pressure not required to operate siphons

therefore use less energy ,

but im assuming the greater the flowrate between GB and FT is better for fish health, certainlly in regards to oxygenation , but possibly better environment for bacteria

so if a reduced water pump size is utilized by 'Chop' or 'constant flood' technology , oxygenation will have to be boosted by another means

comparisons i have seen with different growbed configurations largely focus on plant growth , but this is only half of the purpose of these 'growbeds'
cheers ben

[Murray]

a constant height, (constant flood) gravel growbed would require less flow , because pressure not required to operate siphon

You do not require "pressure" to operate bell siphons. In fact we have found the exact opposite. In order to effectively distribute the water via the distribution grid for a constant flow / flooded system a lot more pressure or pump performance is required than is required for a bell siphon.

But look, to each his own. We are not talking about earth shattering differences.

[benwalters]

"In order to effectively distribute the water via the distribution grid for a constant flow / flooded system a lot more pressure or pump performance is required "
thats interesting Murray, so ebb and flow is an efficient method of delivering moisture evenly into a grow bed,

im still interested in the rate of water exchange between GB and FT, is the greater the flow the better for bacteria?, as water should be more airated

i have some growbeds that dump 10 +times per hour directlly into growbed from looped multi- siphon 1 meter higher than FT and it uses a 4500 water pump to do this, but i feel im getting a lot of oxygen back, but perhaps there are better ways,
all the best
Ben

[Gratilla]

"Constant Flood" has been discussed at length, and comparison tests have been run, here and elsewhere. Some are in favour of it, some aren't. The end results were similar when compared to Flood & Drain using an auto siphon, and Timed F&D systems.

Two rupiahs: I have to admit to being increasingly "aren't"; not only with respect to Constant Flood, but also E&F, F&D, Floating Raft and NFT ie pretty much all the hydroponic side of AP as they are currently practiced. The main reason being that I can't believe that terrestrial plants can grow optimally while their roots are permanently inundated. Even with the F&D systems - members appear to take pride in maximizing the number of F&D cycles per hour. Under these conditions the roots never have a chance to "drip dry" before the next flood cycle. ie They are permanently "breathing" through a film of water.

Consider:

- The maximum solubility (ignoring supersaturation) of oxygen in water (at atmospheric pressure and 25 deg C) is 8.3mg/l. That's 8.3ppm (parts per million). More at lower temps and higher pressures.
- The amount of oxygen in the atmosphere is around 21%. ie 210,000ppm
- That's 8.3 vs 210,000ppm - magnitudes of order greater.

Which would you prefer to breath while running a marathon?

Here is a quote I plagerized from http://www.indg.in/agriculture/agricultural-best-practices/sri/agri-best-sri. (The rest of this page also makes interesting reading.) It describes Jesuit Father Lelaunie's thinking in developing his counterintuitive principles of the highly productive System of Rice Intensification - SRI.

"Everybody believes that rice is an aquatic plant and grows best in standing water. Rice is not an aquatic plant; it can survive in water but does not thrive under reduced oxygen (hypoxic) levels. Rice spends a lot of its energy to develop air pockets (aerenchyma tissue) in its roots under continuous inundation. Nearly 70% of rice root tips get degenerated by flowering period."

Don't you find it amusingly ironic that while the rice-growing world is drying out its flooded paddies (to one F&D cycle per day), the aquaponics community is rushing in the opposite direction.

Is this heresy?

[Murray]

I guess we could talk about it all day, but the fact remains that plants grow extraordinarily well in AP grow beds and DWC and NFT systems. The rice paddy "standing water" would be very oxygen depleted.

Which would you prefer to breath while running a marathon
I guess this would be a useful comparison if we could find a way to get our plants to run alongside in a marathon....:) Sorry, I am not wishing to make light of your point here, but the comparisons between humans and plants re oxygen requirements and methods of oxygen take up is not in any way applicable.
Similarly, a rice paddy flooded with stagnant water bears little resemblance to a functioning AP system.

[joeyd]

Hi

I have 3 flood and drain grow beds in my green house. At the moment during the day when it is hot I set them to flood by removing the bells. This helps new seedlings with short root systems and enhances growth, it also stops them from wilting. When things cool down I simply return the bells.

Cheers

Joey

[RupertofOZ]

Likewise Joey, and at other times I vary the time duration of the flood & drain.. even leaving them off altogether overnight during winter...

But the key Gratilla... is that our systems are constantly re-oxygenated... they don't become oxygen depleted... and/or stagnant...

And you'll find oxygenation widely adapted in DWC and NFT... even in hydro operations...

[benwalters]

Joey- good idea to establish seedlings

Also interesting discussion re. optimum oxygen requirement for plant roots,
reminds me of the idea of growing plants in a fog with no medium, forgot what it was called ?, airoponics?

Anyway, the posts i have made on this thread were primarily to discuss the merits of various irrigation methods and the impact of these on fish health, (perhaps it is off-topic)
As soon as we are talking about grow beds everyone starts talking about plants, when the grow beds more vital function is to keep fish happy (fish are more fragile and costly)

I am not running a 100 watt pump 24hrs day, all year long for the purposes of irrigating 3 square metres of garden beds, to meet the needs of the plants
This is obviously excessive for plant needs
so im doing it because i believe the fish like it
so im wondering if various irrigation methods yield greater efficiency in reaping oxygen from the growbed, or are more efficient in providing the necessary conditions for our bacterial friends
I doubt, and feel free to correct me on this , that a constant height system, could provide as good aerobic conditions to host bacteria, this is partly common sense and partly my interpretation of Murray's comments above

whether there is a big difference, who knows?
what is the optimum ebb/flow or flood and drain cycle ??
i cant say, but perhaps experiments have been done that could make conclusion on the rate of nutrient conversion, and D.O. under different regimes, per unit of power


cheers,
ben

[Gratilla]

... the fact remains that plants grow extraordinarily well in AP grow beds and DWC and NFT systems.
It's difficult to have a constructive dialogue against unsubstantiated subjective hyperbole that's presented as fact. "Extraordinarily well"? "Extraordinarily well" implies that there's little room for further improvement, which is in fact not the case. Take for example another gas that is indispensible for plant growth, carbon dioxide. Current ambient around 390ppm (compared with 240ppm pre-Industrial Revolution). There are literally thousands of research documents showing that growth for most plants can be increased in excess of 50% by increasing the CO2 to 1200ppm. It's disappointing that no-one appears interested in quantitatively evaluating AP performance. "Extraordinarily well"? "Adequate" is more like it.

And what about this?
9431
The picture shows floating raft lettuce. How would you explain the lettuce in the center of the jpg that is directly over an airstone. The peripheral lettuce is over normally oxygenated water. If the latter are doing "extraordinarily well", how are the ones in the middle doing?


... the comparisons between humans and plants re oxygen requirements and methods of oxygen take up is not in any way applicable.
Incorrect. In fact method of oxygen uptake by humans and plants is remarkable similar - via osmosis over a semi-permiable membrane using differential partial pressures. Humans can also successfully "breath" a liquid. Not water, which carries insufficient oxygen, but perfluorocarbons etc, which do.


Similarly, a rice paddy flooded with stagnant water bears little resemblance to a functioning AP system.
Which part of left field did "stagnant" come from. I have never heard of rice being grown in stagnant paddy; usually in fields with running water - in one end and out the other. Even ignorant uneducated peasants are aware that oxygenated water is necessary for rice to survive.

And if you really want to duke it out, groan for groan:

I guess this would be a useful comparison if we could find a way to get our plants to run alongside in a marathon....:)
What? You never heard of runner beans!

[RupertofOZ]

And what about this?
9431
The picture shows floating raft lettuce. How would you explain the lettuce in the center of the jpg that is directly over an airstone. The peripheral lettuce is over normally oxygenated water. If the latter are doing "extraordinarily well", how are the ones in the middle doing?


Gratilla, I for one am not opposed to mcuh further "quantatative research in aquaponics being undertaken...

But posting a photo of an obviously poorly designed and operated floating raft... just doesn't mean all such systems perform poorly...

Take the one below for instance... just one of many of thousands...

And the photo of the bridge... does it imply that all bridges are likely to fail... obviously not... the one behind, an example of a properly designed bridge... is still standing.. ;)

[Gratilla]

... posting a photo of an obviously poorly designed and operated floating raft... just doesn't mean all such systems perform poorly.

Rupert, could you be specific as to how the floating raft is "obviously poorly designed"?

And as for your floating raft - the guy in the background doesn't look too happy with his cauliflowers. And who could blame him?

The bridge? What's the difference in design between the two bridges? I can't see from the distance.

[RupertofOZ]

Rupert, could you be specific as to how the floating raft is "obviously poorly designed"?


No worries... the system is obviously under oxygenated... and attempts to alleviate the problem.. by the placing of a single aeration point... highlight it...

Seriously Gratilla... you can find hundreds of photos and youtube videos... that show consistant, even growth through raft systems... because they're obviously properly oxygenated...

And similar oxygenation requirements, and techniques are/have been widely known and used in NFT style hydroponics... :rolleyes:



And as for your floating raft - the guy in the background doesn't look too happy with his cauliflowers. And who could blame him?

What cauliflowers... the photo pictures bok choi... and the photo is from a trial research facility here in Australia...

And I can assure you that the operators are very happy with the results so far.. ;)



The bridge? What's the difference in design between the two bridges? I can't see from the distance.

One of the bridges was obviously poorly designed, had inherent design flaws... or the design was poorly implemented...

It fell down... the other is still standing... :(

The point I was making was that a single picture of a failed system... doesn't represent all such systems, or designs...

[SustainableHarvest]

Which part of left field did "stagnant" come from. I have never heard of rice being grown in stagnant paddy; usually in fields with running water - in one end and out the other. Even ignorant uneducated peasants are aware that oxygenated water is necessary for rice to survive.

:trout: Regarding Rice Paddies,

Perhaps its the rice paddies in rural Japan that you are referring to, with references being made with running water in and out - continiously. The Japanese farm leveled paddies and divert streams for that purpose. This is not a common practice in NE Thailand where soils are weak with low nutrition levels.

In 3 years my wife and I have managed 3 main rice crops, and one 2nd season rice crop. This year we had production in 3 locations (2 of which were shared cropping on a 1 year partnership). The paddies involved were either rain fed, or pump fed to hold a desired water level, No stream flow involved, no water exchanges involved, no access to government project irrigation water.

The paddies themselves had great yield. While the water in the paddies is stagnant, it was not low oxygen by any means. The paddies uptake oxygen from rain and from wind transfer on the surface. They also nightly condense water from high humidity conditions of the rainy season, fully saturated with oxygen at temperature equilibrium conditions. These aspects of the rice paddy eco system keeps paddys viable for rice cropping.

The paddies also form a light algae content, that generates oxygen by photosynthesis. The life forms in the paddies are very diverse, frog populations, fresh water crabs, mud fish, turtles, even field mice / rodents. Plenty of insects, spiders, and different predators abound. A rice paddy has its own eco system, whether it uses stagnant or moving water. They are not low oxygen environments.

The only time water moves through a paddies in Thailand, is because the water is passed through to fill another rice paddy. Once full, rice paddies are held at a desired level. Sometimes water is released due to heavy rainfalls and high levels in the paddy. That is about the extent of any water movement for many rice farmers in Thailand.

Even farmers who are lucky to have irrigation project water sources, take only the water they need to fill their paddies. They do not flow excessive irrigation water through their paddies.

Your understanding of rice cultivation and common practices is out of touch with the practices commonly used in Thailand, and much of SE Asia.

While many rice farmers in Thailand struggle economically, and have limited education. Any description such as "ignorant uneducated peasants" is a very unflattering and an unfit term to apply. That term imply's no culture or value system exists for them, when in fact quite the opposite is true.

Many farmers in my town are my friends. Life in a small rural farm community marches to a different pace, and revolves around a different set of values. People depend more on their neighbors and their family, because no social safety nets exist here.

My education level is beyond a masters level (measured by credit hrs). I am retired after a career where I carried large responsibilities. managed professionals, and had to execute critical judgments often. I hold a belief that there is something that can be learned and appreciated about almost everyone we meet over a lifetime.

Amid the global climate challenges, post peak oil energy challenges, Food security / prosperity challenges, and rising Geo-policitical tensions and polarizing public policy debates, perhaps its to shed some of the Elitist views. You should re-think your view regarding "ignorant uneducated peasants" before you toss that label out there to folks who farm for a living.

[tpilk]

Excellent post SH - you've summed up farming in SE Asia quite well.

As a part of my job, I regularly travel to 7 countries is SE Asia and work with many rural people. "Ignorant, uneducated peasants" is not a fair description or assessment for the many people who carve out a living from the land here. I have experienced local frustrations with the introduction of technology and outsiders trying to "Westernize" the locals. The bottom line is that they've taken what the have at hand and through knowledge passed down or in some cases modified due to unexpected challenges, they make it work.

As you know, this past year was extremely challenging. I expect the changes and/or "modernization" will come in the form of water management on a grand scale. This will be good. It will be interesting to see how things trickle down to local farmer and his way of life.

Cheers

[Gratilla]

Phew, obviously one can get into a lot of trouble from not using smileys! SusH, can I call you SusH? SustainableHarvest is rather a mouthful before my first coffee. You can call me Grats, if you like. Or even G; but I kinda draw the line at G Whiz, G Spot or G String. Of course, if you insist on formality, then SustainableHarvest it is. And you can call me by my full title - Gratilla the Pun. :)

<Deep breath!>

1) Stagnant: SusH/SustainableHarvest, you're not entirely wrong. :)

1a. In order to jump into the debate on "stagnant", you need to understand its context/use history in this thread. "Standing" water, not "stagnant", was first used (by myself) in a quote to contrast flooded vs non-flooded paddy. Murray unfairly converted :) this to "stagnant" and Rupert twisted the knife :) by repeating. In context, the latter implies "stale or foul from standing" [dictionary definition] with little or zero oxygen, which as debating tactics go is not entirely cricket. :)

Still grow your rice in "stagnant" water? Or "standing" water?

1b. For the past decade I've resided in rural Indonesia on the southern coastal plain. Rice here is grown "usually in fields with running water" during the rainy season, temporarily plugged during fertilizer application. I admit to being ignorant of how your friends do things in NE Thailand. Perhaps I'm just not interested. :)

2) Uneducated/Ignorant: No value judgement or insult intended, as I think is clear from the context. The poor farmers of Madagascar are often referred to as "uneducated peasants" when discussing their 10+ton/hectare yields ... in contrast to the educated pea ... rice farmers of Australia who can only average around 7tons/ha (FAO figures). I've already admitted ignorance of the detailed practices of the rice farmers of NE Thailand, but your assumptions in the second half of your post are pretty much off the mark (and also rather presumptious). <no smiley>

I prefer to let my words stand (or otherwise) on their merits (or otherwise) and don't make it a point to announce (and rest on) my educational laurels, my honorary titles or my (unpaid) public works ... but I assure you, you do NOT want to get involved in a pissing contest. <no smiley>

Now, judging from the planting patterns and pre-harvest panicle development in the pictures in your nicely done link (which requires some heavy proofing, BTW), I would infer that you're still using traditional planting methods and that your harvested results are rather modest.

Care to supply a figure? I'd be (pleasantly) surprised if you break 3tons/ha.

[RupertofOZ]

1a. In order to jump into the debate on "stagnant", you need to understand its context/use history in this thread. "Standing" water, not "stagnant", was first used (by myself) in a quote to contrast flooded vs non-flooded paddy. Murray unfairly converted :) this to "stagnant" and Rupert twisted the knife :) by repeating. In context, the latter implies "stale or foul from standing" [dictionary definition] with little or zero oxygen, which as debating tactics go is not entirely cricket. :).


Well actually... the first mention of "stagnant" was...

Originally Posted by benwalters


so a constant flood situation needs a fair bit of flow to keep water from becoming stagnant


You then went on to quote from a publication... which quoted "standing water"


Everybody believes that rice is an aquatic plant and grows best in standing water. Rice is not an aquatic plant; it can survive in water but does not thrive under reduced oxygen (hypoxic) levels.

Then addressed the issue/debate about "constant flood" with this observation...


Don't you find it amusingly ironic that while the rice-growing world is drying out its flooded paddies (to one F&D cycle per day), the aquaponics community is rushing in the opposite direction.

Is this heresy?


Several posts later..

Originally posted by Murray


The rice paddy "standing water" would be very oxygen depleted.


Murray did then go on to say... in the same post...


Similarly, a rice paddy flooded with stagnant water bears little resemblance to a functioning AP system.


I then responded to a post by Joey.. and addressed this comment to you... in response to your post, and query regarding "heresy"...

Originally posted by RupertofOZ


But the key Gratilla... is that our systems are constantly re-oxygenated... they don't become oxygen depleted... and/or stagnant...


So frankly, I think everyone has been entirely within context... and the flow of the context...

And indeed... in many ways... are saying the same things... perhaps just not to your liking...

I don't think I "stuck the knife" into you at all... but was merely following the flow of the discussion...

Your arguement seems to be that rice benefits from long drain, or non-flood periods... so that oxygenation doesn't become depleted... in a "standing" water body.. which would oherwise become "stagnant"...

And then infer that aaquaponic systems, including those that run a constant flood... would somehow also become oxygen depleted...

I, and others.. were merely suggesting that AP system are constantly re-oxygenated... to prevent this from occuring...

[benwalters]

Hi ,i have found this post interesting,
Good to have debate without too much personal jives
We all come from different backgrounds and can get the wrong end of the stick from time to time...
I think debate about oxygen requirement is interesting
plants can obviously grow very well in all sorts of situations
Has anyone got any feedback on my reference to 'Airponics' i found some on youtube, not sure if it is a commercially viable, but it does indicate that moisture can come in may forms

also interested in a response on the concept that in backyard AP the grow bed main function is as a filter for fish, plants requirement are not as critical, (running pumps for sake of fish not so much for plant needs) but i suppose fish and plant health go hand in hand

I'm still interested if anyone has any input as to frequency of flood and drain cycles and how it impacts on the health of the biological filter, particularly in regard to energy efficiency.
I.E. Do bacteria prefer flood and drain?, any tests done?, maybe the bacteria prefer long gaps between flooding?
Perhaps this is better address in a new post, of maybe i should search old posts.....

anyway good to here from all you all wherever you may be, peasant or otherwise
cheers
ben

[RupertofOZ]

Ben.. the BYAP trials show little difference between frequent fast fill / fast drain bell siphons... constantly flooded... and timed (15/45) overflow standpipe...

As to Aeroponics... it was a bit of a fad... but just not that practical... and unless the nutrient mix was well filtered... prone to blockages... and /or root problems...

And that was in hydroponics... :wink:

[benwalters]

Ben.. the BYAP trials show little difference between frequent fast fill / fast drain bell siphons... constantly flooded... and timed (15/45) overflow standpipe...
John, does the above comment refer to bacterial ability to process nutrients, and impact on irrigation regimes on D.O in water after being in GB?
if so were measurements taken to assess this, or was fish / plant health the measure?






As to Aeroponics... it was a bit of a fad... but just not that practical... and unless the nutrient mix was well filtered... prone to blockages... and /or root problems...

And that was in hydroponics... :wink:

interesting, i imagine the technology required to produce a fine mist is high tech and not easy to maintain, but i guess it shows growth can happen with many different moisture application techniques
But no great rush to apply those techniques to ap !!
thanks for info
cheers
ben

[RupertofOZ]

Ben... ph, ammonia, nitrites, nitrates, water usage... and comparative plant growth were all tracked...

Judge for yourself... http://www.backyardaquaponics.com/forum/viewtopic.php?p=253752#p253752

[Gratilla]

Moving along from (but not ignoring the main issue of) your context analysis in the first two thirds of your post:

Your arguement seems to be that rice benefits from long drain, or non-flood periods... so that oxygenation doesn't become depleted... in a "standing" water body.. which would oherwise become "stagnant"...

The argument is not argument any more; it is scientific fact, that rice benefits greatly from getting its oxygen from the 210,000ppm in air rather than the 9.1ppm or less in DO. As Jesuit Father Lalaunie stated, "rice can survive, but not thrive in flooded paddy" (DO unspecified), implying that rice/plants cannot thrive or reach their full potential while inundated. Greatly reducing the flood period is one of the central tenets of SRI, a system that is gaining increasing popularity in SE Asia.

... in many ways... [we] are saying the same things... perhaps just not to your liking...

You're right, what is being said is not to my liking for the very reason that we are not saying the same things. I am trying to say that without comparison, without quantitiative metrics, it is impossible to say whether AP growbeds experience adequate, average, optimum or whatever results.

I have been providing comparisons: a) rice before and after SRI, b) lettuce directly above an airstone and not, whereas you have been showing attractive pictures but no context. Your pak choi could be impressive, but not if it were supposed to be cauliflower (you missed that one), or it were supposed to be a meter high, or if it had been growing for 6 months. Did the Research Institute look at root slides under a microscope? How do they oxygenate their water? An airstone under each plant? I don't know. Do you?

The only other person I remember giving comparative observations (and I apologize if I missed someone) was Trout and his measurements that showed his plants in wicking beds (ie not inundated) far outperforming the plants in his various AP (inundated) GBs.

Oh, and BTW:

I don't think I "stuck the knife" into you at all...

Please, I didn't say, "stuck the knife", I said "[twisted] the knife :)". Hardly comparable. [See the :)?]

[benwalters]

John , wow ,thanks for pointing me to the tests, i haven't read it yet, but it occurs to me that they should harvest all the fish at some point and weight them!
but then again, i see there is a recording of feed used in each system, Based on this, timed flood and drain is marginally in front , with constant flood second and autosiphon 3rd. but not much in it.
I would have expected autosiphon to generate the most oxygen, but this appears to be wrong
quote from a member in conversation with john. -
"the more time the water is exposed to the media and bacteria, the more efficient and productive the nitrification."
hence F & D more contact with gravel, better result,
so if using autosiphon it may be best to slow down cycles

but i need to read entire post from BYAP

In my mind it would be interesting to see an experiment that was linear , i.e measure fish water out( different size fish, age, feeding habit)after a week , cycle in separate plant system for a week , see how much garden bed strips out of water in a given time frame (measure water , dump it ). maybe just use one plant like mint in growbed to rule out any ups and downs in growth, maybe then cut mint weigh it, do it all again
this could give some data on stocking density require for given yield
i believe if we understand how many fish we need to grow a crop it would be beneficial
anyway , have a good night all
cheers ben

[RupertofOZ]

The argument is not argument any more; it is scientific fact, that rice benefits greatly from getting its oxygen from the 210,000ppm in air rather than the 9.1ppm or less in DO.

As Jesuit Father Lalaunie stated, "rice can survive, but not thrive in flooded paddy" (DO unspecified), implying that rice/plants cannot thrive or reach their full potential while inundated.


I'm not arguing the validity of the study Gratilla... very few plants perform "while inundated".... as most of the oxygen uptake is through the lateral oxygenating roots.... (not through the "210,000ppm air" through the leaves)...

Nature provides such a "flood" (rain) and "drain" (seepage/drying)... for exactly that reason....

And it's exactly the simulation of that natural system/design... that "flood & drain" aquaponics is based upon...

I too was surprised as to how well constantly flooded systems performed... and can only conclude that it is due to the constant reoxengenation of the system.. by aeration from water return and/or additional air pumps...




I am trying to say that without comparison, without quantitiative metrics, it is impossible to say whether AP growbeds experience adequate, average, optimum or whatever results.


Compared to what.... from my own experience.. in relation to soil gardening, hydroponic growing, and aquaponic growing... (I've done all three... and often at the same time)....

Aquaponics out grows, out yields, and out performs timewise... in relation to the others...

Have you actually tried aquaponics yourself....

And if not, then looking through the 1000's of member systems online throughout the world... how do you explain the prolific growth...



I have been providing comparisons: a) rice before and after SRI, b) lettuce directly above an airstone and not, whereas you have been showing attractive pictures but no context.

But your comparisons are invalid Gratilla.... you compare a soil based culture system... to a very poorly designed and implented raft system... and totally ignore the directly relevant (contextually) raft system example I provided...

It's not overly surprising to me that a plant crop... in this case rice.... benefits from adoption of exactly the irrigation/drainage techniques that are usually applied to almost all agricultural cropping...

But you then make bold assumptions, and assertions... or at least direct inferences... that this is due to increased oxygen intake from the atmosphere... when in fact, your own example supports the theory that it's actually due to improved oxygen uptake through the plant lateral roots... (demonstrated by the fact that when inundated rice attempts to trap air around it's roots...

And totally ignore other possible factors... such as for instance... that the increased oxygen availability may be significantly aiding hetrotrophic bacterial breakdown of what would otherwise be submerged detrius... allowing mineralisation/fertilisation/"fertigation" of the crop... increasing yield...




Your pak choi could be impressive, but not if it were supposed to be cauliflower (you missed that one),


No I didn't... it is definitely pak choi.. not cauliflower...



... or it were supposed to be a meter high, or if it had been growing for 6 months. Did the Research Institute look at root slides under a microscope? How do they oxygenate their water? An airstone under each plant? I don't know. Do you?


Well yes I do actually... the fish tanks supplying the water are highly oxygenated... as are the solids digesters... and the rafts themselves have "soaker" type aeration through out the length of the rafts...

And I can tell you Gratilla... that the very first thing I look for... to determine the health of the plants, and efficiency of the system... in either raft style aquaponics, or hydroponics (and I have many years of experience commercially)...

Is the state of the ROOTS.... and specifically how white, clean and pristine they are... and the picture I posted is a perfect example...

But it could have been a picture of one of 100's of raft or DWC systems... and I have 100's of them.. both aquaponics, or hydroponics... and there are 100's of them posted all over the internet...



Please, I didn't say, "stuck the knife", I said "[twisted] the knife :)". Hardly comparable. [See the :)?]

True you did say "twisted" the knife as opposed to "stuck"...

Which just goes to show how meaninglessly pedantic you are being...

Gratilla... build whatever system you want, or feel comfortably with...

Or better yet... build a series of parallel systems implementing different techniques... re-invent the wheel to your own liking.. and then make your judgments and post them if you wish...

At the moment... most of your comments are actually just "speculations"... and at times IMO... misinterpretations...

[Gratilla]

... very few plants perform "while inundated".... as most of the oxygen uptake is through the lateral oxygenating roots.... (not through the "210,000ppm air" through the leaves)...

Exactly. But when I quoted Dudley Harris' requirement to leave an air space at the top of the roots as necessary for supplying oxygen from [the 210,000ppm in] air, you poo-pooed it as being outdated and superceded by oxygenated DWC systems, which inundate roots with 9ppm oxygen at best. (The "leaves" is a left-field distraction; we're discussing exclusively roots.)


Nature provides such a "flood" (rain) and "drain" (seepage/drying)... for exactly that reason....

And it's exactly the simulation of that natural system/design... that "flood & drain" aquaponics is based upon...

Nonesense. Nature doesn't F&D @ 4 cycles/hour. If nature wanted to permanently inundate roots and demand that they got their oxygen from DO, it would have allowed them to evolve into aquatic plants. Perhaps the aerenchyma cells are just an evolutionary response to asphyxiation.


I too was surprised as to how well constantly flooded systems performed...

Compared to what...
Ah yes, F&D, DWC, etc ... but not a system that allows roots to be fully oxygenated.


Aquaponics out grows, out yields, and out performs timewise...[soil gardening and hydroponic growing]
But not, apparently, wicking beds which yet again you [in]conveniently ignore.


It's not overly surprising to me that a plant crop... in this case rice.... benefits from adoption of exactly the irrigation/drainage techniques that are usually applied to almost all agricultural cropping...

But you then make bold assumptions, and assertions... or at least direct inferences... that this is due to increased oxygen intake from the atmosphere... when in fact, your own example supports the theory that it's actually due to improved oxygen uptake through the plant lateral roots... (demonstrated by the fact that when inundated rice attempts to trap air around it's roots...

WTH do you think I've been saying for the last umpteen msgs??? At least I can be thankful that you accept that I can support my own "theories".


True you did say "twisted" the knife as opposed to "stuck"...

Which just goes to show how meaninglessly pedantic you are being...

If I were "pedantically" correcting your lack of attention to irrelevant detail, then maybe you'd have a point. However, it was your ignorance of the smiley (ie netiquette) I was drawing your attention to. Obviously you missed that one too.

I'll pass ... on the gratuitous insults, but might I suggest that once you've calmed down you visit a wicking bed forum and demand that they waterlog their growbeds with (highly oxygenated) water. Report back with their response. We could do with a good :(

[SustainableHarvest]

Phew, obviously one can get into a lot of trouble from not using smileys! SusH, can I call you SusH? SustainableHarvest is rather a mouthful before my first coffee. You can call me Grats, if you like. Or even G; but I kinda draw the line at G Whiz, G Spot or G String. Of course, if you insist on formality, then SustainableHarvest it is. And you can call me by my full title - Gratilla the Pun. :)

<Deep breath!>

1) Stagnant: SusH/SustainableHarvest, you're not entirely wrong. :)

1a. In order to jump into the debate on "stagnant", you need to understand its context/use history in this thread. "Standing" water, not "stagnant", was first used (by myself) in a quote to contrast flooded vs non-flooded paddy. Murray unfairly converted :) this to "stagnant" and Rupert twisted the knife :) by repeating. In context, the latter implies "stale or foul from standing" [dictionary definition] with little or zero oxygen, which as debating tactics go is not entirely cricket. :)

Still grow your rice in "stagnant" water? Or "standing" water?

1b. For the past decade I've resided in rural Indonesia on the southern coastal plain. Rice here is grown "usually in fields with running water" during the rainy season, temporarily plugged during fertilizer application. I admit to being ignorant of how your friends do things in NE Thailand. Perhaps I'm just not interested. :)

2) Uneducated/Ignorant: No value judgement or insult intended, as I think is clear from the context. The poor farmers of Madagascar are often referred to as "uneducated peasants" when discussing their 10+ton/hectare yields ... in contrast to the educated pea ... rice farmers of Australia who can only average around 7tons/ha (FAO figures). I've already admitted ignorance of the detailed practices of the rice farmers of NE Thailand, but your assumptions in the second half of your post are pretty much off the mark (and also rather presumptious). <no smiley>

I prefer to let my words stand (or otherwise) on their merits (or otherwise) and don't make it a point to announce (and rest on) my educational laurels, my honorary titles or my (unpaid) public works ... but I assure you, you do NOT want to get involved in a pissing contest. <no smiley>

Now, judging from the planting patterns and pre-harvest panicle development in the pictures in your nicely done link (which requires some heavy proofing, BTW), I would infer that you're still using traditional planting methods and that your harvested results are rather modest.

Care to supply a figure? I'd be (pleasantly) surprised if you break 3tons/ha.

Your reply post to mine is a fair reply. I dont come to this board to have pissing contests, like most people my time is more valuable that wasting it on that. Perhaps I judged you too harshly and quickly, but I have to tell you that your post which made degrading references to rice farmers angered me. Your comments on rice production is inaccurate for much of SE Asia.

I take it at face value that you meant no disrespect to rice farmers. I dont normally step up on a soap box to tout my education or experience, but from the language of your post I felt compelled to make clear that you I do not fit the mold of the rice farmer you referenced. I do not rest on academic laurels, carry honorary titles, or perform unpaid public services.

If you were standing in any rural Thai village addressing the public and referred to rice farmers the same way as your post....Most locals would step up and give out a bad beating.

I do not think your recognize the tone of the other two portions of your post before you comment on rice production.

In your first quote, you grill Murray's quotation, inferring that his puts out unsubstantiated subjective hyperbole as facts, devoid of quantitative evaluation. Pretty harsh slap, for someone who pays the freight for the discussion board.. Don't you think ?. They you quote a well known statistic about CO2 and plant growth, and take a slap at many on the thread by saying you are disappointed that it appears that no one is willing to apply quantitative evaluations to AP performance.

You read FAO, you've seen the protocols used for their studies, obviously you know a quantitative evaluation requires rigor across disciplines, and trials with controls to be accurate and totally objective. Most people using this board, do not have the time to devote to that.

In your next quote, you shoot down another poster with a quote about the human and plant oxygen demand and uptake processes. You say point blank they are wrong, and that Humans and plants are very similar, because they share the same gas transfer across a semi-permeable membrane. Clearly Humans and plants oxygen demands and processes are far more dissimilar than similar. The membrane issue is a very small part. When was the last time you saw a human take in a net positive uptake of C02 for many hours of a 24 period to support physiological processes ? What about humans discharging oxygen on a net basis for the other portion of a 24 hour period, also for their physiological benefit ? The answer it has never. The poster you quoted was correct, there is no similarity between humans and plants for oxygen demand or processes they experience. You toss on more extemporaneous facts about preflourocarbon fluids that are pretty meaningless to the posters quote. This tactic is pure misdirection, it if far removed from the quote you dispute.... like a magician performs for his audience to achieve his illusion.

The tone and point of view displayed in your response to this first two quotes, sets a perception.... that you are confrontational and take no prisoners in discussions. Your tone was out of balance with the sentiments and observations offered by others. You were on the attack.

When I read the first part of your post - those thing stood out. Not really enough of an item to react to... but the next quote that involved some universal view of rice production and those engaged in farming that crop... It was a item, I felt needed correction.

These 3 items collectively caused me to cast a label on your point of view. Likely unjustified as I do not really know you. It is good that you choose to stand by your words whether they hold merit or not, that is what most people do. Did you thing I expected some kind of retraction here ???? This is an open public forum, where everyone is entitled to their opinion, and should act with civility and discretion. I crossed the line, in response to the posture you displayed here.

I will admit to overstepping my bounds, and will watch myself in the future. People who have read this board a lot longer than I have, likely know all your contributions here and accept the way you choose to communicate. No problem - they will form their own opinions as well

Regarding your direct questions.

My rice paddies hold standing water, not stagnant water.

Regarding rice crop yields:

Crop 1: 0.70 T/Ha. Drought year, poor water mgmt, scatter planted, 3.52 ha in production. Other area farmers averaged 1/3 of normal yield as well

Crop 2: 2.23 T/ Ha Drought year, average water mgmt, transplant method, 3.52 Ha in production. Crop was stressed from abnormal wet season.

Crop 3: 3.33 T/ Ha, Dry season, irrigated 2nd crop, 1.2 Ha in production, Rice type: Regular Thai White Rice (shorter cycle than Homily rice)

Crop 4a: 3.03 T/ Ha, Great water mgmt, machine planted, 1.12 Ha in production, Rice type: Thai Fragrant Rice "Homily"

Crop 4b: 2.72 T/ Ha, good water mgmt, scatter planted, 0.32 ha in production, Rice type: High Glutenous rice "Sticky rice"

Crop 4c: 1.22 T/Ha, Dry year, no reserve water available, scatter planted. 4.8 Ha in production. Rice type: Thai Fragrant Rice "Homily"

Crops 1, 2, 3, 4a were grown on my farm. 4b grown in same town, 4c grown 5 hours away. Moving ahead with the current systems used, my rice yield will remain similar to Crop 4a. Comparing farming in NE Thailand (on the Korat plain) to Malaysia, is like comparing Apples and oranges. It will be interesting to see what you have to say about these rice yields.

It is far better not to stray this far off topic.

[Murray]

But not, apparently, wicking beds which yet again you [in]conveniently ignore.

That is only one members report (Trout I believe) and that is fair enough, that has been his experience. For me, my AP system outperforms wicking beds consistently, but I have to say, not by all that much. Wicking beds are pretty good , but not as good as AP, IMO. But it is for a different purpose, I use my wicking bed/s to grow sweet potato and the like. When I have grown trials of lettuce etc, the AP system outperforms the wicking bed, easily. I would not even attempt to grow sweet potato and the like in AP.

That is not to say anything bad about one system or the other. A smart gardner will employ several methods and enjoy the benifits of each on his dining room table at meal time.


I dont come to this board to have pissing contests (from SustainableHarvest)

So true, argument is futile in the end. This is a place to share ideas and each of can gain and share valuable info.

[SustainableHarvest]

That is only one members report (Trout I believe) and that is fair enough, that has been his experience. For me, my AP system outperforms wicking beds consistently, but I have to say, not by all that much. Wicking beds are pretty good , but not as good as AP, IMO. But it is for a different purpose, I use my wicking bed/s to grow sweet potato and the like. When I have grown trials of lettuce etc, the AP system outperforms the wicking bed, easily. I would not even attempt to grow sweet potato and the like in AP.

That is not to say anything bad about one system or the other. A smart gardner will employ several methods and enjoy the benefits of each on his dining room table at meal time.



So true, argument is futile in the end. This is a place to share ideas and each of can gain and share valuable info.


Comments above are well said. Adapting growing techniques for specific crops seems to be goals everyone is looking for, and understanding at a deeper level. Improving the processes used, to maximize resources, minimize energy footprints, benchmarking plant & fish yield are all very worthwhile discussions of the highest order.

I have found the brief comments on this thread connected to rice and it growth process with a roll-out comparison pointing to different AP processes to very interesting and deeply thought provoking. Causing me to review in my own mind 3 years of observations from growing rice from my farms changing experience, and from what I have seen in practice on other farms from traveling the secondary roads and looking at paddie work and seasonal preparation.

Grat's reference to SRI and a hint of its foundation, as well as his challenge for me to state my crop yields (in T/Ha) has been very eye opening. In 2008 I took a short look at an article that pointed to a possible emerging new practice for rice. It seemed focused on water scarcity and the concept of single seedling planting to save resources. My perception was these "concepts in testing", were not really suited for SE Asia. Dismissing that article viewed in 2008 and rejecting it usefulness was a mistake on my part.

Looking into SRI today, reading for several hours, published details reveal SRI techniques have become a well proven process. I have not seen them in use on any rice farm here. Even the government rice research farm 25 km from my home concentrate on rice strain development testing only.

Despite many perceptions, rural Thailand agriculture operates with a labor shortage most of the time. Rainfall intensity in Thailand's principal rice season make it a challenge to keep fields in a non flooded state. These issues make full SRI methods difficult to deliver here. None the less it is worth time and effort to see what aspects of SRI can be introduced in my area with some adaptation. SRI was discussed at lunch today, with my partner and we have agreed look at and adapted SRI trial on one section (about 50%) of the 1.12 ha farm plot committed for rice next year. That cycle will begin in May.

In all, this is a direct spin off of the dialogue from this single thread, on this board. I have to pass on a great gratitude to the voices from this thread, for having a powerful impact on things that come under the radar for consideration. Thank you. BR - Pat

[Mr. Mik]

..
...
In all, this is a direct spin off of the dialogue from this single thread, on this board. I have to pass on a great gratitude to the voices from this thread, for having a powerful impact on things that come under the radar for consideration. Thank you. BR - Pat

Very interesting how the most acrimonious threads often become the most useful ones...:p

Mik

[RupertofOZ]

Ok.. I've been off doing a bit of research before replying... and the reply isn't intended as a"pissing match".... but to correct what I think are some misassumptions...


Exactly. But when I quoted Dudley Harris' requirement to leave an air space at the top of the roots as necessary for supplying oxygen from [the 210,000ppm in] air, you poo-pooed it as being outdated and superceded by oxygenated DWC systems, which inundate roots with 9ppm oxygen at best. (The "leaves" is a left-field distraction; we're discussing exclusively roots.)


Firstly... you didn't quote "Dudley Harris" anywhere that I can find... I looked through all my hydroponics books, which are in storage since my move... and couldn't find my "Dudley Harris" books to check your claim...

But regardless....

Yes, it is correct to say that the oxygen of air can be stated as 210,000ppm...

And yes the oxygen content of most bodies of water... typically ranges from about 5-9ppm...

Factually the oxygen content of water (ignoring super saturation as you did previously)... can range from 0-14.... depending on atmospheric pressure, elevation (a direct relationship between the two)... and temperature...

And yes oxygen is taken in by the plant leaves during photosynthesis.. and could be said therefore to be at a concentration of 210,000ppm...

But oxygen uptake by roots is a function of osmotic diffusion... i.e the oxygen uptake is via moisture/water... (and nutrient uptake- closly related - plant root systems require oxygen for aerobic respiration, an essential plant process that releases energy for root growth and nutrient uptake.)...

This is shown by the first sign of inadequate oxygen supply to the roots... as wilting of the plant under warm conditions and high light levels.... Insufficient oxygen reduces the permeability of the roots to water and there will be an accumulation of toxins, so that both water and minerals are not absorbed in sufficient amounts to support plant growth.

As you've already said... and science attests to.... water typically, has a fixed DO content... that isn't even a fraction of 210,000ppm...

You challenge me...



I suggest that once you've calmed down you visit a wicking bed forum and demand that they waterlog their growbeds with (highly oxygenated) water. Report back with their response. We could do with a good :(

But as you are the one that questions the proposition... Well Gratilla... I'd actually like to challenge you...

Setup three wicking bed containers based on the following criteria...



300mm deep
Fill with a loose fast draining media - allowing plenty of air void spaces... I suggest either hydrotron expanded clay, or blue metal gravel
In the first - Install a standpipe, with two small holes at the base of the standpipe...
In the second - Install a standpipe without any holes...
In the third - install a bell siphon
Install a media gaurd around all three standpipes...
Collect the drainage water in a tank
Aerate the collection tank
As the media is basically inert - you'll need to supply some nutrients for the plants.. I suggest using fish...
Flood the first system to about 25mm below the media surface.. (adjust the standpipe height accordingly)... for 15 mins every hour... use a timer to initiate the pump on/off cycles
Flood the scond system to about 25mm below the media surface.. (adjust the standpipe height accordingly)... by continuous pumping
Flood the third system to about 25mm below the media surface.. (adjust the standpipe height accordingly)... by continuous pumping
Plant the same vegetables in all three beds
Observe, note and report results


If you aren't able, or willing to undertake this experiment... but would like to see the results of exactly such a trial...

See this link...http://www.backyardaquaponics.com/forum/viewtopic.php?p=253752#p253752

:D

[Gratilla]

Ok... I've been off doing a bit of research before replying... ... to correct what I think are some misassumptions...

Firstly... you didn't quote "Dudley Harris" anywhere that I can find...

Firstly, what I said was (different thread, but in a dialogue with yourself):

From "Hydroponics" by Dudley Harris Ch 3 Section on Water Culture:
"It is important to leave an air-space of about 12 to 25mm between the bottom of the frame and top of the nutrient solution. As the roots of the plant grow, the volume of the nutrient can be reduced slightly until a 50mm air-space exists. This space is necessary for supplying oxygen to the roots of the plant."
and I stand by this. The quote is verbatim (the underline is mine) from:

Hydroponics - The Complete Guide to Gardening Without Soil by Dudley Harris MSc, ISBN 1 85368 193 8, 1998 reprint, page 23, last paragraph

And if you really really pretty please, I'll scan you a bladdy copy and email as an attachment! :) [NB Pls note the smiley.]

Secondly, what misassumptions? I'm assuming (but that might be a misassumption) that you mean my misassumptions, but it looks more like a list of agreements while you correct your misassumptions. The first hint at a possible disagreement is the "But oxygen..." halfway down your post, but what follows is perfectly reasonable and not at odds with what I've been saying.


You challenge me...

But as you are the one that questions the proposition... Well Gratilla... I'd actually like to challenge you...
Although a) your timing is good (we're in the final stages of completing 18 circular 2m diameter GBs from what used to be shrimp tanks) and b) I'm usually up to a good challenge, why would I want to (Now how did you put it? Ah yes.) reinvent the wheel when you kindly give results of the experiment in your message?

BTW, what was the "proposition" again?

[Gratilla]

Your reply post to mine is a fair reply.
Thanks. There are a few (actually quite a few) things in your post I disagree with, but nothing worth falling out over. Moving on.


Regarding rice crop yields:
The yields on your harvests are disappointing, but with scope for significant improvement. The last time I looked, average yields for developing countries was in the order of 3+T/Ha and for developed countries (who could throw a lot of capital, fertilizer and chemicals at their crops), just over 7T/Ha, but at this point they hit something like a brick wall with diminishing returns on increasing inputs - one of the major reasons reports of the yields being gained by the uneducated Madagascans were treated with disbelief. The IRRI (International Rice Research Institute) in the Philippines even went so far as to have a peer-reviewed article in Nature Magazine published declaring that one of the reasons for the reported high yields was poor record keeping (cf uneducated peasants! Geddit?) - after they themselves had failed to reproduce similar crop levels. They were immediately attacked in the next issue by a group of agriculture scientists blaming the IRRI of poor science (and implying hidden agendas). All good stuff.

My personal classification of rice growing methods is 1) traditional, 2) Modern (IRRI), 3) Aigamo/Pati and 4) SRI.

IRRI is characterized by hybridization and strain selection in addition to GMO development, although reportedly not for commercial release. High capital availability, artificial fertilizers and agricultural chemicals.

Traditional lacks much/most/all of the above.

Aigamo/PATI: This integrates rice, azolla, ducks and (optionally) fish. Rice/ducks/fish invariably beats rice/ducks/azolla (personal communication - by a Belgian University professor doing research in the Philippines, so properly quantitative). Paddy, planted in the usual way, is inoculated with (fast-growing) azolla and (once the rice plants have recovered from transplant stress) ducklings are added. The ducks eat weeds, insects, golden apple snail (a major pest in our areas) and azolla. The do NOT eat the rice plant, much to the surprise of farmers. They do, however, eat rice florets and, of course, the grain, so need to be taken out of the paddy before the flowers emerge. By this time they are just about ready for market, providing a secondary income for farmers. English translation of the founders original book in Japanese available from the Permaculture Institute in Tasmania.

SRI: Characterized by heavy use of organic fertilizers/composts, single plant seedling per hill at transplant and wider spacing (to minimize/eliminate root competition), no long-term flooding (to maximize aeration of roots). The target is to produce strong single plants with maximum number of tillers and panicles, high polished grain to raw rice ration and stronger grains minimizing income loss from cracked seeds.

SRI and Aigamo, I believe, can be successfully integrated eg SRI does not stress pest control, so I feel ducks would be of benefit - in addition to the second income, etc, etc, etc.

Lots more, but times short. :)

[RupertofOZ]

and I stand by this. The quote is verbatim (the underline is mine) from:

Hydroponics - The Complete Guide to Gardening Without Soil by Dudley Harris MSc, ISBN 1 85368 193 8, 1998 reprint, page 23, last paragraph

And if you really really pretty please, I'll scan you a bladdy copy and email as an attachment! :) [NB Pls note the smiley.]

No need Gratilla... I can assure that I not only have that book by Dudley... but all of the rest of his works... and those of many others...

(I just couldn't find that particular reference in amongst the stuffed stored...to check it...

But from memory... the system the work referred to... was not a system that was aerated... and with the raft floated directly on top of the water... prevented any natural air diffusion that might assist oxygenation...

There are 1000's of other hydroponic, and aquaponic systems.. that attest to the success acheivable.. by the oxygenation of the nutrient supply...

And flood & drain methodology...

Even the early works of J Sholto Douglas and "The Bengal Method"

Used 300mm beds
Used gravel as a medium
Used a flood and drain methodology




Secondly, what misassumptions? I'm assuming (but that might be a misassumption) that you mean my misassumptions, but it looks more like a list of agreements while you correct your misassumptions. The first hint at a possible disagreement is the "But oxygen..." halfway down your post, but what follows is perfectly reasonable and not at odds with what I've been saying.


Gratilla I was/am challenging your assertion, or inference.. that plants extract their oxygen needs from the air... at a concentration of 210,000ppm... through their roots... and that therefore, as you incorrectly postulate.. that all F&D, DWC, NFT systems.... even if aerated are likely to fail, or be less productive...

Likewise, your interpretation of the SDI rice trials... as proof of the assertion that plants uptake their oxygen needs from the 210,000ppm in air... is flawed...

The article you linked to states...



under reduced oxygen (hypoxic) levels. Rice plants spend lot of its energy to develop air pockets (aerenchyma tissue)


But this is true of all plants in reduced oxygen (hypoxic) levels....

As is the statement that "root growth is massive. It receives nutrients from deeper layers of the soil."....

It is the normal response by plants under low moisture, low oxygen conditions... to spread and/or deepen their roots ... to find the greatest availability of nutrients, and water.. to, along with oxygen, transport the nutrients...

Likewise, the increased seed head formation observed... is typical of all plants placed under stress... at the first opportunity, or more favourable conditions... as a survivial and reproductive response...

You only have to peruse the cannibis growing forums to see this in action...

The study you linked too doesn't have "drained" root exposed conditions at all...



Under SRI paddy fields are not flooded but kept moist during vegetative phase. Later only one inch water is maintained..


So again your assertion, or misinterpretation that exposing the plant roots to 210,000ppm air... is not correct....

The technique also quotes less plants/area, higher labour maintence costs...

Yes it does suggest higher yields, and less water usage.. all good things...

But the rest of your extrapolations aren't valid... especially when you attempt to use them in comparisons to hydroponic and/or aquaponic F&D techniques and results...

Build an aquaponics system Gratilla... and prove to yourself.. that the methodology does work... even if in the end you feel that the yield, costs, time etc for other methods ... i.e wicking beds... is better...

[Gratilla]

I sometimes feel like I've entered the twilight zone.

Gratilla I was/am challenging your assertion, or inference.. that plants extract their oxygen needs from the air... at a concentration of 210,000ppm... through their roots... and that therefore, as you incorrectly postulate.. that all F&D, DWC, NFT systems.... even if aerated are likely to fail, or be less productive...
The underlined words are about the only ones that are vaguely close to anything I've asserted.

What I said was that plants that are permanently inundated, even with water oxygenated to the maximum, cannot reach their full potential.

Before I gave up on your repeated mis-assertions completely, I went over to http://aquaponicscommunity.com to try to find the "lettuce circle" thread and stumbled on this first: http://aquaponicscommunity.com/forum/topics/trough-aeration-increases?groupUrl=raftdeepwaterculturegrowers&groupId=4778851%3AGroup%3A28261&id=4778851%3ATopic%3A34512&page=1#comments. I thought I'd died and gone to Heaven. I found sentences and phrases like:

"- I have seen several aquaponic farms in the area that have been adding supplemental aeration in their troughs and getting dramatic increases in plant growth in the immediate area of the aeration. ..."

- O2 is directly related to growth rates so the higher the better.

- etc, etc.

And then I found this picture (thumbnail below). I rest my "proposition".

Thumbnail Text: This trough has 3 soaker hoses running down the length. The middle hose has clogged up and is no longer putting out bubbles. The difference in growth is very apparent.

[RupertofOZ]

I'm glad you found some of the many, many 100's of DWC floating raft systems that when correctly oxygenated... work extremely well Gratilla.... even when the roots are constantly inundated....

Perhaps now you understand that the original picture you posted... is an aberation... not the norm... even when the rafts are floated directly on the water surface... unlike the "Dudley"method....

Likewise, I can assure you that F&D systems work just as well... and even NFT benefits from oxygenation...

I'm glad that you've finally come to agreement...

[Yabbies4me]

So when's the engagement party?... :D
.

[Gratilla]

So when's the engagement party?... :D
.

You're welcome to join us at the head-against-a-brick-wall bash. :D

[Gratilla]

I'm glad ...

(Bio)Chemistry 101: The rate at which a chemical reaction proceeds is determined by the concentration of the reactants; the reaction rate will increase/decrease with increasing/decreasing concentration.

Similarly, plant productivity is determined by the concentration of certain reactants.

For example, increasing CO2 ambient concentration will increase productivity; decreasing CO2 ambient concentration will decrease productivity.

You've already admitted that decreasing the concentration of oxygen in water has an adverse impact on plant health and productivity, so you must also admit that increasing oxygen concentration in water increases plant productivity. However, you apparently believe that productivity hits a brick wall at the maximum solubility of oxygen in water. I don't. I believe that injecting bubbles into the water allows plants in the immediate vicinity to take advantage of the increased concentration of oxygen in the air in the bubbles when the bubbles adhere to the roots.

Just as Einstein believed that the maximum velocity of an object was limited by the speed of light, you apparently believe that the maximum productivity of a plant is limited by the maximum solubility of oxygen in water.

You're BOTH WRONG!

Live with it.

[tpilk]

Rather than the "Google" science lesson, what is YOUR AP setup showing you?

[RupertofOZ]

Oh dear... indeed a science lesson might prove beneficial...


Similarly, plant productivity is determined by the concentration of certain reactants.
In general... true... but lets address the two points you make in seperate posts...

Firstly...


For example, increasing CO2 ambient concentration will increase productivity; decreasing CO2 ambient concentration will decrease productivity.
Well you might think so... and conventional wisedom has suggested this is the case...

New research suggests that sure, increased CO2 will make crops more productive, but the quality of the crops may be degraded.

Much of the data on the effects of enhanced CO2 on plants come from so-called chamber experiments, where a plant is grown in a greenhouse or closed container with varying levels of CO2.

The advantage of such experiments is the ability to carefully control the plant’s growing conditions. The disadvantage is that the growing conditions are artificial and we can’t be sure if the plant’s behavior resembles what would occur in the real world.

To address this issue, scientists have developed an open-air approach called the Free-Air Carbon Dioxide Enrichment (FACE) experiment, in which field crops (or forest stands) are exposed to continuous high levels of CO2.

These free-air, real-world experiments provide a bridge between the more controlled chamber experiments and what the future might hold.

Without question, wheat is a staple crop. How wheat responds to enhanced CO2 is a big deal, and FACE study results are not encouraging: while wheat yields increase, its protein content drops.

Take a recent German study published in Plant Biology for example. Petra Hogy of the University of Hohenheim and colleagues compared wheat grown under today’s conditions (with CO2 levels at about 387 parts per million) with those projected for the year 2050, with CO2 levels around 550 ppm.

Hogy’s team found about a seven percent drop in protein content, noting several other changes in nutritional value:

amino acid concentrations decreased, with greater reductions in non essential rather than essential amino acids;
minerals such as potassium, molybdenum, and lead increased;
minerals such as manganese, iron, cadmium, and silicon decreased; and
sugars including fructose and fructan increased.


A number of other (mostly chamber) studies suggest that the toxicity of some crops will increase with rising CO2 levels. Of particular concern is cyanide.

About 60 percent of today's crop plants are cyanogenic, meaning that when their leaves are chewed or crushed, cyanide is released as a defense mechanism.

A series of papers by Roslyn Gleadow of Monash University and her colleagues find that many cyanogenic plants will have greater cyanide toxicity when CO2 concentrations are higher.

While we humans don’t usually eat clover, foraging animals like cows and sheep do, so how clover responds to elevated CO2 is of interest.

A recent study led by Gleadow, published in the Journal of Chemical Ecology, found that while cyanide levels in clover grown under ambient (360 ppm) and elevated (700 ppm) CO2 levels did not rise, protein content dropped some 25 percent — in other words, the cyanide-to-protein ratio increased.

This is important because the ability of livestock to tolerate cyanogenic compounds depends on their protein intake. The more protein they take in, the more cyanide the animals can handle and vice versa.

In controlled greenhouse experiments, Gleadow’s group found that the relative ratio of protein to cyanide dropped by 30 percent or more, suggesting that livestock will be exposed to greater amounts of cyanide in a CO2-enhanced world.

This could also mean that livestock may need to forage more to get the same amount of protein to combat the cyanide, which could lead to other downsides like more waste and methane production.

Cassava, also called manioc, is a cyanogenic staple that supports hundreds of millions of people. The starchy tuber’s leaves and roots are critical to tropical populations in Latin America, Africa, and Asia, despite its harmful amounts of cyanide.

A Gleadow study published in Plant Biology found that while growing cassava at CO2 levels of 710 ppm had no effect on the cyanide in its root, it doubled the plant’s cyanide levels in its leaves and shrank the tuber’s size.

To remove the cyanide and make it safe for eating, cassava is generally rasped, fermented and dried, but residual amounts remain. In a typical year, for instance, flour in Mozambique markets has been found to have cyanide levels ranging from 20 to 40 ppm but in a drought year (cassava is a very drought-resistant crop), cyanide levels have been found to be as high as 100–200 ppm. The World Health Organization recommends a limit of 10 ppm cyanide in food.

Cyanide poisoning, which can be fatal, can disrupt normal endocrine function and impair neurological function. Konzo, a form of cyanide poisoning that causes leg paralysis, already affects nine percent of Nigerians.

Not a good situation, and one that could grow unless alternate cassava varieties are developed with lower concentrations of cyanogenic compounds. (And strangely at present, according to the Encyclopedia of Food and Culture, ''many farmers prefer to cultivate the high-cyanide varieties for reasons that are not entirely clear.'')

All these studies at the intersection of crop nutrition and enriched CO2 levels illustrate the complex ways that the natural system can respond to changes and perturbations which in turn can have serious ramifications for humans.

[RupertofOZ]

Now.. let's turn to oxygen, and oxygenation... as this is continually where you seem to make continuing assumptions... or misinterpretations based on either mis-assumptions, or mis-understandings of principles...


You've already admitted that decreasing the concentration of oxygen in water has an adverse impact on plant health and productivity, so you must also admit that increasing oxygen concentration in water increases plant productivity.
Well I certainly agreed that raised levels of oxygenation promoted plant productivity... so let's accept the above...



However, you apparently believe that productivity hits a brick wall at the maximum solubility of oxygen in water. I don't. I believe that injecting bubbles into the water allows plants in the immediate vicinity to take advantage of the increased concentration of oxygen in the air in the bubbles when the bubbles adhere to the roots.



The amount of air that can be dissolved in water increases with the system pressure and decrease with the temperature.

The solubility of air in water can be expressed as a solubility ratio: Sa = ma / mw (1)
where
Sa = solubility ratio
ma = mass of air (lbm, kg)
mw = mass of water (lbm, kg)

Henry's Law

Solution of air in water follows Henry's Law - "the amount of air dissolved in a fluid is proportional with the pressure of the system" - and can be expressed as: c = pg / kH (2)
where
c = solubility of dissolved gas
kH = proportionality constant depending on the nature of the gas and the solvent
pg = partial pressure of the gas

The solubility of oxygen in water is higher than the solubility of nitrogen. Air dissolved in water contains approximately 35.6% oxygen compared to 21% in air.

Solubility of Air in Water

Temperature (oF) Gauge Pressure (psig)
0 20 40 60 80 100
40 0.0258 0.0613 0.0967 0.1321 0.1676 0.2030
50 0.0223 0.0529 0.0836 0.1143 0.1449 0.1756
60 0.0197 0.0469 0.0742 0.1014 0.1296 0.1559
70 0.0177 0.0423 0.0669 0.0916 0.1162 0.1408
80 0.0161 0.0387 0.0614 0.0840 0.1067 0.1293
90 0.0147 0.0358 0.0589 0.0750 0.0990 0.1201
100 0.0136 0.0334 0.0536 0.0730 0.0928 0.1126
110 0.0126 0.0314 0.0501 0.0699 0.0877 0.1065
120 0.0117 0.0296 0.0475 0.0654 0.0833 0.1012
130 0.0107 0.0280 0.0452 0.0624 0.0796 0.0968
140 0.0098 0.0265 0.0432 0.0598 0.0765 0.0931
150 0.0089 0.0251 0.0413 0.0574 0.0736 0.0898
160 0.0079 0.0237 0.0395 0.0553 0.0711 0.0869
170 0.0068 0.0223 0.0378 0.0534 0.0689 0.0844
180 0.0055 0.0208 0.0361 0.0514 0.0667 0.0820
190 0.0041 0.0192 0.0344 0.0496 0.0647 0.0799
200 0.0024 0.0175 0.0326 0.0477 0.0628 0.0779
210 0.0004 0.0155 0.0306 0.0457 0.0607 0.0758

Example - Calculating Air Dissolved in Water

Air dissolved in water can be calculated with Henry's law.

Henry Law's Constants at a system temperature of 25oC (77oF)
• Oxygen - O2 : 756.7 atm/(mol/litre)
• Nitrogen - N2 : 1600 atm/(mol/litre)
Molar Weights
• Oxygen - O2 : 31.9988 g/mol
• Nitrogen - N2 : 28.0134 g/mol
Partial fraction in Air
• Oxygen - O2 : ~ 0.21
• Nitrogen - N2 : ~ 0.79
Oxygen dissolved in the Water at atmospheric pressure can be calculated as:
co = (1 atm) 0.21 / (756.7 atm/(mol/litre)) (31.9988 g/mol)
= 0.0089 g/litre
~ 0.0089 g/kg
Nitrogen dissolved in the Water at atmospheric pressure can be calculated as:
cn = (1 atm) 0.79 / (1600 atm/(mol/litre)) (28.0134 g/mol)
= 0.0138 g/litre
~ 0.0138 g/kg
Since air is the sum of Nitrogen and Oxygen:
ca = (0.0089 g/litre) + (0.0138 g/litre)
= 0.0227 g/litre
~ 0.023 g/kg
Calculating air dissolved in water for some other pressures at temperature 25oC (77oF) can be summarized to:
Pressure, abs (atm) 1 2 3 4 5 6
Dissolved Air in Water (25oC) (g/kg) 0.023 0.045 0.068 0.091 0.114 0.136


How does O2 dissolve in water?

The oxygen has to cross the air/water interface- a process known as diffusion... often a slow process.

Just how slow depends on whether the water is still or running, how much surface is in contact with the air, what's dissolved in the water, and whether any films (like soap, or broken bacteria or algae cell walls) are floating on the surface.

Once the oxygen crosses the surface, it is caged by water molecules.

Where the air and water meet, this tremendous difference in concentration (and related pressure)... causes oxygen molecules in the air to dissolve into the water.

More oxygen dissolves into water when wind stirs the water; as the waves create more surface area, more diffusion can occur.

(A similar process happens when you add sugar to a cup of coffee - the sugar dissolves. It dissolves more quickly, however, when you stir the coffee.)

Another physical process that affects DO concentrations is the relationship between water temperature and gas saturation.

Cold water can hold more of any gas, in this case oxygen, than warmer water. Warmer water becomes "saturated" more easily with oxygen. As water becomes warmer it can hold less and less DO

Dissolved oxygen concentrations are most often reported in units of milligrams of gas per liter of water - mg/L. (The unit mg/L is equivalent to parts per million = ppm).

DO - % saturation

Oxygen saturation is calculated as the percentage of dissolved O2 concentration relative to that when completely saturated at the temperature of the measurement depth.

Recall that as temperature increases, the concentration at 100% saturation decreases. Elevation, the barometric pressure, and the salinity of the water also affect this saturation value but to a lesser extent.

The DO concentration for 100% air saturated water at sea level is 8.6 mg O2/L at 25°C (77°F) and increases to 14.6 mg O2/L at 0°C.

See the charts below...

[RupertofOZ]

So what's it all mean Gratilla.... in terms of your arguments....

Plants absorb oxygen through their roots... by osmotic diffusion... of oxygen dissolved in water.... not from oxygen contained in air pockets around roots... or from air contained in bubbles (more in a minute)...

Oxygen is dissolved in water by diffusion.... and relates to pressure, elevation, and temperature.... but there are physical limitations to solubility of oxygen (from air) in water...

Oxygenation/diffusion occurs at the surface interface of the water and air.... and is greatly increased by agitation....and proportional to the surface area of the water exposed to the air...

This is why paddlewheels are so efficient as aerators... and..

This is why finer bubbles from air stones are preferred as opposed to larger bubbles... because they disturb a greater surface area of the surface of the water... allowing a greater amount, and rate of diffusion...

The bubbles DO NOT aerate the water as they rise... to exchange any air inside the bubble they would have to break.... they don't...

Now still bodies of water... still conditions, whether by meterology, or plant cover, (like say a rice paddy).... or by say... floating raft type systems.... .... that prevent, or limit the diffusion of air exchange to water.... are likely to result in declining, and depleting DO levels... UNLESS OXYGENATED....

Not supposition... but scientific FACT...

(There are also possible detremental effects from limitation of offgassing of CO2 with rafts floated directly on top of the water... again alleviated by oxygenation...)


Just as Einstein believed that the maximum velocity of an object was limited by the speed of light, you apparently believe that the maximum productivity of a plant is limited by the maximum solubility of oxygen in water.

You're BOTH WRONG!

Live with it.

Sorry Gratilla... I might not be an Einstein.... but you're the one that's wrong... totally wrong...

[Yabbies4me]

:eek:... OMG you guys!

Roll on Feb 17th hey Rupe!... :p
.

[RupertofOZ]

Yeah... temperature should be beginning to decline... leading to higher DO levels... and availability of trout...

And the plants will just keep on growing... unless I suffocate them... by sucking the oxygen out of the water.. by too many fish, too higher levels of feed vs too little filtration... or by low flow rates and stifling air exchange at the surface of the water... with say, a floating raft...

But it's OK.... I'll just add an external aerator.... and raise the DO in my water... I've heard it works... from about xxxxxxx people...... :rolleyes:;):D

[Yabbies4me]

You could just try adding a few glugs of Hydrogen Peroxide! :D


Roll on Feb 17th hey Rupe!...

http://www.afl.com.au/nabcup/fixture/tabid/15297/default.aspx

Then at least you'll have something to occupy your currently under stimulated mind! :p
.

[RupertofOZ]

Yeah... I knew you meant the footy was starting Yabs... just trying to keep the thread on topic... ;)


You could just try adding a few glugs of Hydrogen Peroxide! :D


And please don't go throwing stuff like that into the equation.... we'll probably end up having a discussion about whether or not dogs look better with blonde hair...

[Yabbies4me]

Yeh... I knew you knew... I was just trying to change the topic! :D
.

[trout]

The bubbles DO NOT aerate the water as they rise... to exchange any air inside the bubble they would have to break.... they don't...



Hi Rupe

This statement has been repeated numerous times and every time I see it, it
doesn't sound logical.

Firstly oxygen will transfers from air to water as long as there is a gradient and
will do so until an equilibrium is reached.

secondly, the air/water interface is the same regardless whether it's at
the surface or 100 metres under water.

thirdly, air bubbles consist of 78% nitrogen and 21% oxygen (with some minor other stuff) so even if it could transfer all its oxygen the bubble size would
reduce to 79% of its original size but not break as you stated.


fine bubble diffused aeration is able to maximize the surface area of the bubbles and thus transfer more oxygen to the pond per bubble. Additionally, smaller bubbles take more time to reach the surface so not only is the surface area maximized but so are the number of seconds each bubble spends in the water, allowing it more time to transfer oxygen to the water. As a general rule, smaller bubbles and a deeper release point will generate a greater oxygen transfer rate.[6]

ref http://en.wikipedia.org/wiki/Water_aeration

Now the quote above makes sense to me.
But Wiki being Wiki you need something else.

http://techalive.mtu.edu/modules/module0001_alt/OxygenMassTransfer.htm


The rate of oxygen mass transfer , i.e. from the gas (air bubbles) to the liquid phase (water) is governed by the terms described below.


dC = Kl . a . (Cs-C)
dt

where
Kl is liquid film transfer coefficient for oxygen (m•d-1)
a is the ratio of bubble surface area to water volume (m-1)
Cs-C is the oxygen deficit (g•m-3)

As you see the surface doesn't come into the calculation at all.
It's all about surface area and the oxygen deficit gradient.

I would appreciate some links you have that proves this one way or the other.

cheers Lou

[bigdaddy]

Hi folks,

You may have answered the post in simple terms and I have missed it,... but all I can see right now is reams and reams of Gobblygook, and I can't understand the answer, or have forgotten it... So to recap...The answer to Kev's first post is?......In everyday garden variety language I mean...Whistling:):24locos:

Cheers.

[benwalters]

Hi, Bid daddy, ive been following this post and i think that the answer to kev's question is -
constantly flooded beds have been tried and they work,
in fact they MAY work better than other methods
especially in cycling systems
some plants don't grow as well in these systems, but others do very well
according to tests done by BYAP mob
http://www.backyardaquaponics.com/forum/viewtopic.php?f=51&t=8621&sid=8d08996de04f25ca0aa9756f70080eca



It may be that the flooded bed need good flow rate and oxygenated water to be successful
I think it would be good if flooded systems are periodically fully drained by taking out stand pipe

In the long term some systems may turn out to have advantage over others
Plants seem to grow in lots of different irrigation types
(Im not sure what the implications of various methods for fish growth)

basically it all works

cheers
ben

[RupertofOZ]

Lou, what you say, and link to is valid and true.... but the crux, and understanding lies in the parts which you didn't underline... rather than that which you did...

Yes the air in a bubble will diffuse into water... according to the "surface area and the oxygen deficit gradient"....




fine bubble diffused aeration is able to maximize the surface area of the bubbles and thus transfer more oxygen to the pond per bubble

Yes, finer/smaller bubbles do take more time to reach the surface so not only is the surface area maximized but so are the number of seconds each bubble spends in the water, allowing it more time to transfer oxygen to the water....

But diffusion is a slow process.... and the amount of diffusion that occurs as the bubble travels up from an aerator (usually only a metre at most)... in the time it takes for the bubble to reach the surface, usually only seconds.... is effectively only miniscule...

The majority of the diffusion and oxygenation occurs at the surface...


Most of the "diffuser" style aerators that are referred to, especially those employed in aquaculture.... are utilised more for the purpose of lifting and mixing low oxygen deeper water to the top... where the increased surface area of the bubbles... and diffusion oxygenates the water.... and by mixing the lifting water increases DO throughout the pond...

Paddlewheels are so efficient as aerators... because of the vast surface area of water they expose to air as they toss the water into the air...

And likewise... running mountain streams, rapids etc... are so highly oxygenated... for the same reason...

[Gratilla]

I have a small floating raft grow bed where the roots work their way down to the water and the top half of the plant is dry. I got to thinking, what would happen is we had a gravel grow bed that was constantly flooded with the exception of 2 or 3 inches at the top. The plants could be planted in the dry gravel and be watered by capillary action.

Any Thoughts?

The two would be equivalent, IMO.

The capillary action of gravel is not that great - the smaller the gravel size, the better. I don't see the relevance here, unless you're trying to dampen the top part of the roots. More important would be maximum aeration of the water. Bubbles help, IMO.

Keeping the top part of the roots dry(ish), to allow full aeration of the lateral roots, is in line with professional opinion. Some people prefer to submerge the full root, which is not optimum IMO.

[Gratilla]

Oh dear... indeed a science lesson might prove beneficial...

<sigh> Well, if you really really insist.

Lesson 1: Seek first to understand... [Stephen Covey: "The 7 Habits..."].

I'm largely familiar with the studies you quote. Your extensive references to these would be more credible, though, if you had bothered to read (and understand) beyond the "sound bites" of the summaries. Example:


Without question, wheat is a staple crop. How wheat responds to enhanced CO2 is a big deal, and FACE study results are not encouraging: while wheat yields increase, its protein content drops.

What the full text tells us is that protein content remains statistically the same in absolute terms; carbohydrates (understandibly) increase in absolute terms, thus in relative terms carbohydrates increase wrt protein and, of course, proteins decrease proportionally. And this is exactly in line with scientific expectations (carbon dioxide being a precursor to sugars, carbohydrates, etc <We don't need to do Photosynthesis 101, do we?> and contributes nothing directly to proteins).

Your version is misleading. Intentionally?

Lesson 2: Laminar Flow vs Turbulent Flow:


More oxygen dissolves into water when wind stirs the water; as the waves create more surface area, more diffusion can occur.


At high (turbulent) wind velocities, the contribution of increased water surface area to rate of oxygen diffusion is modest. A much greater contribution to the rate of oxygen dissolution would be from the oxygen depleted air at the water surface being replaced by fully oxygenated ambient air. At low (laminar) airflows, contributions from increased surface area would be ... ZERO. Pls get it right.

Lesson 3: Gold



A number of other ... blah, blah, ... cyanide ... blah, blah, ...<yawn>

If you're going to throw EVERYTHING into a friendly discussion, including the kitchen sink, then you may as well include the fact that as cyanide in cassava rises, the incidence of gold nanoparticles in the periphery of the leaves increases. Perhaps you could now add a scientific explanation as to why. You do know why, don't you?


Plants absorb oxygen through their roots... by osmotic diffusion... of oxygen dissolved in water.... not from oxygen contained in air pockets around roots... or from air contained in bubbles...

Tell that to Dudley Harris.


The bubbles DO NOT aerate the water as they rise... to exchange any air inside the bubble they would have to break.... they don't...

Huh!?


Sorry Gratilla... but you're the one that's wrong... totally wrong...

In general [Gratilla]... true...

Make your mind up Rupert. Which is it?


I might not be an Einstein....

Well, you certainly got that right.

Now, you'll have to excuse me - tadpoles have got at my duckweed again.

[Yabbies4me]

o…
......

[Yabbies4me]

m...
......

[Yabbies4me]

g!!!...
......

[RupertofOZ]

:(:(:(:(:(

Too funny for words.... I particularly love the "Laminar Flow vs Turbulent Flow" bit....

I'm going off to get a bowl of water and a straw.... I'll record what happens when I blow throught the straw compared with stirring the water with the straw....

With particular reference to the distribution of the gold nanoparticles.... :(:(:(

[RupertofOZ]

At high (turbulent) wind velocities, the contribution of increased water surface area to rate of oxygen diffusion is modest. A much greater contribution to the rate of oxygen dissolution would be from the oxygen depleted air at the water surface being replaced by fully oxygenated ambient air. At low (laminar) airflows, contributions from increased surface area would be ... ZERO. Pls get it right.


In light of these new found facts... I've gone and turned off the paddlewheel aerators in the pond... and erected wind breaks around the pond...

Seems they're a complete waste of time... and the pond will just reoxygenate by itself...

I've also ripped up all the plants in the garden... and pegged them out on the clothsline... where they can breathe properly...

I'll hose them down with some seasol solution every now and then...

Bob's ya uncle... thanks mate.... to think for years I've been doing it all wrong... when it was all so simple.... :(:(:(

[ZooRod]

you sure worms will be ok in a constantly flooded grow bed? I'd like to add some soon and well wouldnt want them to run away or die.


i assume 'constant flood" and "continuous flow" are the same thing
plant growth may be comparable in these systems
but comparisons i have seen on forum do not measure the ability of the grow bed to host bacteria, and oxygenate water,

continuous flow may have energy benifits though

re. worms, the grow bed is not completelly flooded, and worms can apparentlly handle water if it is oxygen rich

ben

[RupertofOZ]

As long as the system is oxygenated... the worms will be fine Rod.. trust me... ;)

[Gratilla]

New found facts? It's the way clothes dry on a washing line - faster when there's a wind. NB The wind does NOT increase the surface area of the clothes - capiche?

Nowhere in your looong spiel do you mention paddle wheels, etc, etc. What you do say is:


More oxygen dissolves into water when wind stirs the water; as the waves create more surface area, more diffusion can occur.

implying that wind-created waves result in the greatest contribution to increased oxygen diffusion. Which, of course, is nonesense. Paddle wheels are a different matter entirely.

And you, understandably, completely avoid the many (painfully) inconvenient issues.

Your looooong (and largely irrelevant) contribution to a very simple concept reminds me of something. Ah, yes.

Ximinez: NOBODY expects the RoZ Inquisition! Our chief weapon is diversion ... diversion and digression ... digression and diversion ... Our two weapons are digression and diversion ... and irrelevance ... Our *three* weapons are digression, diversion and irrelevance and bluster. Our *four* ... no ... *Amongst* our weapons.... Amongst our weaponry ... are such elements as bluster, irrelevance ... I'll come in again. Oh, and frilly pink knickers.

[From Monty Python - slightly amended]

I don't need a slew of smileys; one will do. :smiley-taunt001:

Have a nice weekend.

[RupertofOZ]

Thank god my clothes are made from gold nanoparticles... they should dry regardless of wind, or oxygen... probably even in a vacumm....

Digression, diversion, irrelevance, bluster... and frilly pink knickers.... :(

I reckon you've got a big girls blouse as well Gratilla... and a man bag as well.... :D

[Castaway]

implying that wind-created waves result in the greatest contribution to increased oxygen diffusion. Which, of course, is nonesense.I'm going to agree with Rupe on this one. Havent read the whole thread so forgive me if I'm off track.
Scroll through to the 7min 40sec mark and listen in on Dr Wilson Lennard a biologist speaking about how water bubbles oxygenate the fish tank. I used to think water bubbles diffused oxygen into the water column as they floated up but apparently that is not correct.

Rupe is as usual with his frilly pink knickers on - is occasionally correct.

iitanQgsk2I

[RupertofOZ]

Rupe is as usual with his frilly pink knickers on - is occasionally correct.


:eek: ... Put your stamp collection away Castaway... philately will get you nowhere.... :D

[fishman]

i have worms all amongst the plant in the raft system and even though it gets a bit manky down the bottom the worms are doing great.every time i pull out a pot the fish geta nice treat.i did not even put them in there,i think they must have crossed over from adjacent beds.
i dont even have aeration inthose beds yet but i have not taken into account the permeablilty of blue barrell plastic to o2 molecules.
sorry i will go back in my hole now
Byron

[Castaway]

Put your stamp collection away Castaway... philately will get you nowhere.... :D

Anyone who wishes to cross swords with Rupe - may I suggest an easier subject like Global Warming or Politics. He has an Achilles heel you know! :D

[Yabbies4me]

Oh!... it was swords they were crossing?... I had an entirely different mental picture going on! :D

[Castaway]

Frilly knickers can hide a lot...

[RupertofOZ]

I wouldn't know about that Castaway... but do tell... :tongue:

[Redneck]

problem with dealing with kiwis is they know all, the only thing that will ever change that is we must tow NZ to antarctica and export all that have ever left the islands back to them and put up a big wall. They are great nieghbours but they visit to often.drinkanimdrinkanimdrinkanimdrinkanim:p

[RupertofOZ]

They are great nieghbours but they visit to often.drinkanimdrinkanimdrinkanimdrinkanim:p

Someone has to do the work Redneck... :D

And the all the good beer is now made in OZ.... by Kiwis... :( drinkanim

[Redneck]

Yes its hard work for me working out which ones the most useless this week and must be replaced.

[trout]

Lou, what you say, and link to is valid and true.... but the crux, and understanding lies in the parts which you didn't underline... rather than that which you did...

Yes the air in a bubble will diffuse into water... according to the "surface area and the oxygen deficit gradient"....




Yes, finer/smaller bubbles do take more time to reach the surface so not only is the surface area maximized but so are the number of seconds each bubble spends in the water, allowing it more time to transfer oxygen to the water....

But diffusion is a slow process.... and the amount of diffusion that occurs as the bubble travels up from an aerator (usually only a metre at most)... in the time it takes for the bubble to reach the surface, usually only seconds.... is effectively only miniscule...

The majority of the diffusion and oxygenation occurs at the surface...



Hi Rupe

The way I see it, the bubbles take a couple of seconds to reach the surface.
Once they hit the surface they break up usually in a lot less time.

The question I would like answered is:

What process magically occurs at the surface to facilitate O2 transfer.
Because I can't see any difference between the air in the bubble underwater
and at the surface.

you say:
"but the crux, and understanding lies in the parts which you didn't underline... rather than that which you did..."

OK, you'll need to explain this to me as I thought I underlined the correct parts.

This study is quite interesting


Analysis of Oxygen Transfer Performance on Sub-surface Aeration
Systems
Kossay K. Al-Ahmady*

International Journal of
Environmental Research and Public Health
ISSN 1661-7827
www.ijerph.org
© 2006 by MDPI

www.mdpi.com/1660-4601/3/3/301/pdf




if the airflow rate is kept
constant, oxygen transfer capacity (OC) is directly
proportional to submergence. At 0.5 m submerges, the
oxygenation capacity is ranging within a narrow limit
between 18-34 grO2/m3water.hr depending on the (f/B)
ratios. With increasing the depth, the oxygenation
capacity is increased to about 160 grO2/m3water.hr at the
4.6 m submerges.

So, this experiment shows that an aerator at 0.5 metre depth will
oxygenate the water to 18-34 grO2/m3water.hr .

But if you put the aerator at a depth of 4.6 metres it will give you
a DO of 160 grO2/m3water.hr,

that's an increase of 4.7 times.

If oxygen transfer only occurred at the surface these two figures should
be the a lot closer about 47.6 grO2/m3water.hr but not 160 grO2/m3water.hr,

Castaway posted the youtube of Dr Lennard stating that oxygenation
occurs at the surface.
I have emailed him requesting verification of that statement, hopefully
he will reply but it is Christmas. Furthermore, gas diffusion and bubble
formation is more fluid mechanics and physics than biology.

So far all the studies I've managed to find suggests and calculates the
diffusion rates of the bubbles to the surrounding water.
None that I've found have ever stated that gas transfer occurs only at
the surface.

In my opinion this last point is very telling.

cheers Lou

[jakesebastin]

Very good information here regarding permanently flooded grow beds. This kind of information is very much helping to the newcomers like me and the others a lot.

[Gratilla]

Seeing as Jake has kindly (although possibly unwisely :D) bumped this thread, I have a question prompted by Jesuit Father Laulanie's quote below:

"Everybody believes that rice is an aquatic plant and grows best in standing water. Rice is not an aquatic plant; it can survive in water but does not thrive under reduced oxygen (hypoxic) levels. Rice spends a lot of its energy to develop air pockets (aerenchyma tissue) in its roots under continuous inundation. Nearly 70% of rice root tips get degenerated by flowering period."

How many members practicing Constant Flood, Ebb & Flow, Flood & Drain, Floating Raft and/or NFT have examined the roots of their plants for aerenchyma tissue (examples can be seen by Googling Images of aerenchyma tissue). Would members who haven't, be willing to take a peek and report presence or absence? Obviously the best time is at harvest.

[Murray]

Interesting Gratilla,
We had a thread going some time back on the possibilities of growing rice in a flood and drain AP system. I actually obtained some certified rice seed but have not made an attempt at it as yet.
A visitor to my place who is a Pakistani guy said he believed that places in his homeland achieve 1kg of rice yield to 1 sqm
Is that a likely prospect ?

Can't find the thread by a quick search.

[Gratilla]

One kg of rice per sq m is equivalent to 10 tons per hectare (ie 10,000 kg/10,000 sq m), which is what the uneducated peasants of Madagascar practicing SRI (System of Rice Intensification) have been getting. Jesuit Father Laulanie, the developer of SRI, before he died (God Rest His Soul) and the more experienced farmers had/have been getting over 12 tons/ha; (the world record being in the order of 27 tons/ha equivalent).

When these figures were first made public they were met with incredulous ridicule, particularly by IRRI who went through a period of denial. SRI methods, however, have now been confirmed and the system is slowly spreading throughout the rice-growing world. I personally believe the method is applicable to other crops, particularly cereals.

More info on SRI at http://sri.ciifad.cornell.edu/ .

I think you'd get good results growing rice in an F&D AP system.


edit:
>>> Can't find the thread by a quick search.
Actually, rice growing was discussed earlier in this thread.