Aeroponics - Can plants grow without soil?

aeroponic-tower-netcup aeroponic-tower-tank-filter
Net cups filled with old coir. Rs.10 tap filter on outlet and inlet.
Filters are excellent. In 2 hours of operation nozzles never clogged. But outlet filters clogged with coir residue resulting in water accumulation in tower. Inlet clogged with dust causing pump inlet of soft pvc to pinch.
Switching 30s on-off reduces problem substantially. But inevitably it will clog.
So coir is out and clayballs will have to be substituted.
@TechNife suggested gravity based trapping (say contained overflow pots) help reduce clogging ?
The towers already have a head of 25mm. I was hoping it would precipitate particles. It does not. Probably the falling water causes sufficient turbulence.
@TechNife I feel some centrifugal + gravity based jugaads incorporated into the flow should yield the most interesting affordable automagic reductions in clogging the filters on the main flow paths. Trials & errors I guess continues.
@vvcstemplay " I also suspect a centrifugal input will considerably reduce the problem. Very cheap faucet extensions have nice little plastic fans in them, moulded on a metal pin. Inserting one in the inlet will set up a nice vortex, that should throw the lightweight coir fragments away from the nozzle."
I was about to test the above suggestions including purchasing some filters from Amazon. But lazy me cooked up a new hightech filter. A HoleeGram Filter
image
A bottle punctured with holes and a sock.
aeroponic-sock-bottle-filter
Pipe is fitted in a hole in the cap.
The ensuing conversation on telegram
@TechNife , [08.12.20 19:10]
[In reply to VicKram Crishna]
showerHeadCentrifugal

@TechNife, [08.12.20 19:10]
@vvcstemplay , Is it this :point_up_2:?

@vvcstemplay [08.12.20 19:52]
[In reply to TechNife]
Yes, I also use one like this in the taps. It prevents water splash, by diffusing the flow.

@vvcstemplay , [08.12.20 19:57]
Of course, the coir particles won’t be removed. So, at some point, you’ll either have to redesign the entire tank system so that the excessively particle filled water is led into a wastewater settling tank, or start using either throwaway or washable filters.

The trouble with a simple settling tank is that the pump evidently causes too much turbulence, and the particles don’t settle under their own weight, or else are less dense and will never settle. If the latter, you can’t use a settling tank at all, and must think about a filtration system.

JT D, [08.12.20 20:45]
[In reply to VicKram Crishna]
Dual tank system. Ideally with a recirculating filter pump. The problem is the higher cost.
However the sock holeegram filter is working well. I removed the outlet filters, so all the debris falls straight into the tank. The much larger surface area spreads the particle trapping and the lower speed stops sucking the larger bits which settles down or floats. Tomorrow i will make 4 more for the outlets. I simply punctured holes with a solder iron. Which catches the sock, making removal a irritant. Tomorrow will drill proper deburred holes. So changing socks becomes simple. Even so not very scalable.

JT D, [08.12.20 20:52]
Changing the bottle and sock together is extremely easy. Just unscrew the cap and screw on a second. If it can function without cleaning for several days, it would drastically reduce routine cleaning.

Three hours of nonstop running without problems. Tomorrow I will make 5 proper HoleeGram Filters with deburred holes and fix 4 on the outflow pipes and one on the inflow of the pump.
@Pneb will also add the electronic control to turn on/off the pump and some level control and alarms.
The PSU used is a PC SMPS used to power Intel Atom motherboards. It is a 400W psu and the 12v section can deliver 20A, well in excess of the 6A required when both motors on the pump is running.

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This entire narrative is so exciting. It takes so many skills to grow plants when we deviate from the natural way. Each parameter needs to be controlled. Whether we grow food from these vertical farms or not, we will grow lots of knowledge from these epistemological gardens.

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Meanwhile others build the instrumentation to read natures encrypted signals.

Abstract

Precision agriculture requires new technologies for rapid diagnosis of plant stresses, such as nutrient deficiency and drought, before the onset of visible symptoms and subsequent yield loss. Here, we demonstrate a portable Raman probe that clips around a leaf for rapid, in vivo spectral analysis of plant metabolites including carotenoids and nitrates. We use the leaf-clip Raman sensor for early diagnosis of nitrogen deficiency of the model plant Arabidopsis thaliana as well as two important vegetable crops, Pak Choi (Brassica rapa chinensis) and Choy Sum (Brassica rapa var. parachinensis). In vivo measurements using the portable leaf-clip Raman sensor under full-light growth conditions were consistent with those obtained with a benchtop Raman spectrometer measurements on leaf-sections under laboratory conditions. The portable leaf-clip Raman sensor offers farmers and plant scientists a new precision agriculture tool for early diagnosis and real-time monitoring of plant stresses in field conditions.
https://www.nature.com/articles/s41598-020-76485-5

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The coir used for filling the netcups is a great attraction for sparrows and a huge problem for us. The sparrows yanks dislodges lots of coir strands, several of which fall inside the tower clogging the drain. So we have to replace the coir with baked clay balls. The ball size is 8mm to 15mm and will fall out of the bottom of the netcup. So we use this vegetable packaging net to line the inside of the netcup. Glass beads being used as a test substitute, since clay balls are yet to arrive.
image

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ATTINY2313 micro running aeroponic pump. Cycle time 30 sec. Duty cycle 50%.
JT D, [17.12.20 18:29]
On the left is a pc psu that powers the board and pump. Pump controlled with relay. Wouldn’t a MOSFET be preferable?

JT D, [17.12.20 18:30]
Timer is interrupt driven.

@Kush_agra_wal, [17.12.20 18:38]
Relay would give perfect isolation between controller and pump hence i guess in this case relay will be a better option and also the selection would depend on how much current is to be switched that depends on pump and i think relay can switch or control more current than MOSFET?

Kushagra Agrawal, [17.12.20 18:39]
Not sure of it👆

JT D, [17.12.20 18:53]
[In reply to Kushagra Agrawal]
True that isolation is excellent. The relay’s inherent isolation is 3.5kv. But PCB layout is very important to achieve that.

JT D, [17.12.20 18:54]
Current draw is 8A. Voltage is 12v.

JT D, [17.12.20 18:56]
There is a rs485 driver so that i can connect to a server like Raspberry PI. Should i use rs232 instead?

Kushagra Agrawal, [17.12.20 19:15]
[In reply to JT D]
But then to draw this max amount of current we would need a high gate voltage to control the switching so it may be possible that micro controller been used won’t supply this through its I/O port? Means again it would need configuration, if possible, to be used?

Kushagra Agrawal, [17.12.20 19:17]
And in this aeroponic farm the data is collected from multiple points or a single point?

JT D, [17.12.20 20:22]
[In reply to Kushagra Agrawal]
Multiple.

JT D, [17.12.20 20:32]
[In reply to Kushagra Agrawal]
To drive the relay we use a transistor. The relay requires 12v. The transistor is TIP122 connected to 12 v. So a gate drive of 12 v is quite feasible. We will save space and have a far longer life for a transistor, but it probably wont save us any money.
#Design optimisation- cost, space, reliability, manufactureability, serviceability…
If we were making several thousand, it would definitely be a MOSFET.

Kushagra Agrawal, [17.12.20 20:42]
[In reply to JT D]
Then rs485…cause i think with rs232 you can connect only one device. Like rs232 was used with db9 cable for printer and computer connection.

Kushagra Agrawal, [17.12.20 20:45]
And selection would also depend on basis which proto is faster among rs485 and rs232 as data would be transferring.

JT D, [17.12.20 21:01]
[In reply to Kushagra Agrawal]
Yes. RS485 is a balanced line multi drop system.
Speed will be slower than a RS232 as it is half duplex - unless we separate the tx and rx lines. However the amount of data is very sparse. So a very low speed would be perfectly ok.

@Anool jokingly suggested a 555 timer
Anool Mahidharia, [17.12.20 18:54]
[In reply to JT D]
Looking good.
Although, a 555 would have done the job !!
:wink:

JT D, [17.12.20 19:04]
[In reply to Anool Mahidharia]
:slightly_smiling_face:. Yes. Unfortunately water level and rs485 link are likely to mess up a 555, though we could implement a 556 level control.

Anool Mahidharia, [17.12.20 19:05]
LOL, just kidding. gotta get in a 55 joke at every opportunity.

JT D, [17.12.20 19:10]
[In reply to Anool Mahidharia]
:grin:. But seriously a fully discrete transistor implementation would be fun.

JT D, [17.12.20 19:11]
After all blokes are building cpus with transistors :wink:

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We now have a fair indication of evaporation from the 160 grow holes on 4 towers.

The volume of water between the lowest permissible level - pump sucking air - and maximum water level is 2.4 li.
In the morning and evening evaporation is approximately 500ml/hr. Midday it climbs to 1.2li/hr. This is at the current peak temperatures of 30^oC. We thus have a peak evaporation rate of 7.5ml per hole per hour. We now have some figure to calculate transpiration as plants grow.

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image
First shoot emerges 4 days after planting Vigna_unguiculata aka chouli. This one uses glass beads. Two more have clay balls as the medium. A few seeds planted Yesterday 22/12/2020. Let’s see how many sprout.
The green mesh vegetable packing net is expected today. This will enable the replacement of the coir with clay balls and planting all the grow holes.

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5 days later (28/12/20)…
image

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image
Vigorous growth. Roots are as long as 15 cm inside the tower.
Replaced coir with clayballs inside a wide meshed packing net placed inside the mosquito net cup on one tower. Planted 10 black eyed beans in each. Replacing coir and planting on all towers in progress. Hopefully this task will be completed by today.
Will add NPKM to water once planting is complete on all towers.
Also removed the socks filter on the 4 outlets, leaving it on the inlet only.

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Planted all the grow holes 2 days ago. The general practice is to germinate and grow until a few leaves appear in a nursery bed, then transplant to the tower. However this is a very tedious process as far as I can tell. So we simply threw 10 seeds into each net cup - first some clayballs, then seeds. then cover with clayballs.
Some problems cropped up with the crop. Sprouts have appeared in all holes. However seeds at the bottom of the conical net cup sprouted inside the tower. This is a major problem as there is very little light inside. These sprouts fall into the tower and clog the drain. Approximately 25% of seeds have germinated inside the tower. Which means poor eventual yields. Also noticed that roots growing thru the mosquito mesh net get constricted somewhat. I had kept the bottom and the seam of the cone open. This proves to be a disaster as some of the sprouts simply grow vertically thru the seam gap, instead of following the cone contour towards the mouth. One cannot correct now as pulling out the cups damages the fragile roots. So will grow this for a few weeks and harvest.
One will require a better method of planting to prevent the seeds from dropping to the bottom of the cone thru the gaps in the clayballs. Also direct the roots towards the open bottom of the cone instead of through the mesh.
More to follow…

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Fascinating. Looking forward to updates.

If you’re using sprinkler nozzles and recycling water and the problem is water pooling, clogging, etc why not put the sprinklers on a timer and not recycle the water? You can use weaker nutrient mix that will keep your nozzle and pump healthier too. 5 min off, 5 sec on, etc - on a cyclic timer. Time it so that roots are moist but there is very little runoff - discard it. No fuss, no clog. Saves electricity too. Occasionally you can run the mist for a longer time with plain water as a rinse.

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Mosquito net is too fine for roots. May be simpler to simply germinate in water and zip-tie the seedlings into place leaving the roots in the air in the tower. Will vary by plant I guess. They will grow to cling to support on their own. Or standard net pots with bigger holes.

The problem isn’t the medium, it is the pot. Some debris will always happen so no point obsessing over planting medium. As plants grow, there will be roots, possibly insects and etc too, so whatever the system is, it will have to be debris friendly. Getting rid of coir won’t solve clogging long term. As support, it is better than marbles, etc.

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Also aeroponics may not be a suitable choice for low budget growing. This tower, for example, could be converted into a much easier to maintain earthworm composter plus growing bin that composts household waste, grows plants and needs no electricity or additional fertilizer. Will try to draw a diagram.

IMG_20210112_013950_compress89

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I immediately checked out to see if I can buy the Raman sensor … Costs more than my plant collection. :joy:

But so useful!

One day,…

I have currently stopped growing vegetable crops sold by local farmers and but from them instead to support, but I have seeds of cyclanthera pedata available if you are interested. Interesting vegetable vine grows similar to cucumber and can be cooked too. Tastes slightly like Shimla mirch but milder. Can be stuffed too. Google it up.

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Isn’t it too short duration for a pump? Or I must be missing something.

I am using sprinkler nozzles with a pesticide spray pump that has two motors. The pump is on for 15 s and off for 30 secs. After 10 cycles stays off for 60 secs. The recycle container holds about 5 liters.
To prevent clogging of nozzle I made a filter out of a plastic bottle and a old sock. Works well - so far no nozzle clog.
https://metastudio.org/uploads/default/original/2X/2/233bd06b1a794902a401b58e43a4ca73f8ef0a21.jpeg

In my case it is both. The cup being circular leaves gaps at the side of the elliptical grow hole pocket. This elliptical hole is an artifact of my construction method and has mostly advantages in the support it provides over a regular hole. However with regular netcup it allows light to leak in and will cause algae growth. It also leads to runoff at the ellipse edge. The mosquito net being conical and very squishy plugs very very nicely into the elliptical blocking light very very well and only very occasional runoff.

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To avoid germinating in a bed and then transplant, an extremely tedious process even with 160 grow holes, never mind the 1000+ setup that I plan, I want to plant in the netcup itself. This works very well subject to avoiding the seedling growing inside the tower.
In order to provide space for roots - especially thicker ones - the net cone is stapled at only one point. This allows the seam to widen to more than 35mm, a property that cannot be achieved with a regular cup. But it also leaves a small gap along the seam, causing the seedlings to grow through the seam INSIDE the tower. A regular netcup will also have the same issue unless it is filled with cocopeat.
The drain clogging is best solved by using 1.5" pipe instead of the 16mm drip irrigation, which I will do at the end of this cycle. The large dia will allow debris to flow into the reservoir where it can be removed easily. Adding a port hole should help too - just stick hand in and clear any clog.

The method we figured to allow growhole planting and avoid all the above problems is to anchor the seed at the ideal spot, which is 10mm before the netcup inner lip edge, using a material that can last multiple grow cycles. We can use cotton gauze or fishtank foam pad or @Pneb idea of using a piece of loofa image .
What better than a natural, spongy, water resistant mesh in which you can just push seed.
However the price is very steep at Rs.30-40 a piece in volumes of 200. Hence the PM to you @Vidyut

I have planted one cup with cotton gauze. It seems to be working. Will know in a day or two.

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No. These are dc motors driving a diaphragm and blocking back flow. If there is back flow, water from the pipe and sprinkler will flow back into the tank. The pump will then have to recharge the pipe before water reaches the nozzle and 10 s will be too short. As there is very little back flow, stopping the pump for several minutes results in spray out of the nozzle in under 2 secs.

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