Passive Hydroponics Thread

[Eric Warwick]

This is a thread for theoretical musings on passive hydroponics that I am combining with a question I have for a couple of systems. I figured any talk about my system plan would spawn a purely theoretical discussion, so I wanted to keep this all on one thread—to make it easier to come back to it. Anyway, past this is my system question, which you can skip if you like.

The above is a crude diagram of the two systems I doodled while in class. The perlite culture is similar to a raised bed with sub-irrigation, except its medium is perlite. The 190L tank feeds the perlite culture with fresh nutrients based on the volume in the tank, using a float valve. Every once in a while (say once a week) I’ll mix fresh nutrients*, and the reservoir will be refilled. The plants planned to be grown range from root crops (radish) to eggplant, to tomatoes, to greens. I’m either going to build it with a shallow strip of H₂O at the bottom, and a capillary mat to separate the two, or more cheaply, with just perlite. The dimensions of the bed are undetermined, but will be dependent on the outflow.

The second system is more self-contained, but needs automation. It stems from a successful experimental design from last year, 2/3 media and 1/3 H₂O. (I was also thinking of DWC.) Since I plan on growing ~20 tomatoes and however many peppers and… I need to get a self-watering system. I was thinking of connecting them with PVC to common reservoir of about 100L, all at equal height. What do ya’ll think of this? Any suggestions? Oh, and don’t worry, I’ll make an aquaponic system eventually, just not this summer. 

*"Organic" nutrients from Fox Farm

[Bart]

I bought a Rubbermaid 30L tote on the weekend and I seeded 8 romaine in 2" net pots so I'm start my little test.
I plan to use the aquaponic water but I am concerned that it will start to smell, did you notice any smell coming from the test you did with the aquaponic water?

[Ted Ansink]

Mine was kept on the back porch and I never noticed any smell coming from it whatsoever.

Bart said:

I bought a Rubbermaid 30L tote on the weekend and I seeded 8 romaine in 2" net pots so I'm start my little test.
I plan to use the aquaponic water but I am concerned that it will start to smell, did you notice any smell coming from the test you did with the aquaponic water?

[Ted Ansink]

Added time lapse pictures of a non-circulating water system using water taken from a commercial aquaponics grower.  No  idea what the nutrient level was when I started, but I have to say that it was easy.

[Bart]

The pics look pretty good to me - definitely worth giving it a shot. I went through the pics a few time, both the hydro and the aquapoinic based ones. it seemed like the aquaponic lettuce grow slowed up towards the end whereas the hydro seemed to be a little more consistent. I'm wondering if there was a bit of an N shortage going on towards the end of the 40 days. They were different variety of lettuce so that might be the explanation I guess. Just wondering if maybe I should plan to swap out the water 2/3rds of the way through the growth to crank up the N level when the plant is nearing the finish line. I guess the key would be to not fill the tub beyond what the water level was so I don't drown any of the oxygen loving roots...........just thinking out loud.................that is usually dangerous

[Ted Ansink]

Bart - I guess the idea of changing the water would depend on what you are doing with the lettuce.  If you are just using it for yourself, you could start with a deeper tote so there would be additional nutrients still in the water at the end.  If you are only doing it like I am for my own consumption, you could just let it go and eat it when it gets to a pickable size and have another one coming up behind it.  I just like having the ease of growing without having to change water or chemicals and I have to admit that I had more lettuce than I needed last summer.  I do agree that if you are going to change the water towards the end of the growing, you should not fill the tub any higher than the water level is when you change it.

[Ted Ansink]

Another non-circulating hydroponics try with Pak Choi.  I let it get carried away and it has started to flower.  I am not sure what is the best way to cook it, but I think I have to do something soon.  For certain veggies the non-circulating way is the easiest way to go.  

[Eric Warwick]

If it's too bitter or tough for a salad, boil it and then put it in a stirfry. Sorry, that was off-topic.

Ted Ansink said:

Another non-circulating hydroponics try with Pak Choi.  I let it get carried away and it has started to flower.  I am not sure what is the best way to cook it, but I think I have to do something soon.  For certain veggies the non-circulating way is the easiest way to go.  

[Vlad Jovanovic]

I've noticed some varieties of Pac Choi seem to bolt/flower sooner than other varieties, if the grow area gets too warm and/or there's too much light. Mei Qing Choi seems to bolt quicker than the Joi Choi I've grown. There's a third variety that I'm just about to try out that is supposed to be somewhat heat tolerant. Guess I'll see in the coming warmer months. Bok Choi is turning out to be one of my favorite inter crops for raft production.

[Eric Warwick]

Well, "baby" bok/pak choi is better tasting, so I don't think bolting is a big problem. Also, can't you put the passive system in a cooler environment? To grow lettuce in Florida, they use chillers--of course you'd use a more sustainable solution.
Vlad Jovanovic said:

I've noticed some varieties of Pac Choi seem to bolt/flower sooner than other varieties, if the grow area gets too warm and/or there's too much light. Mei Qing Choi seems to bolt quicker than the Joi Choi I've grown. There's a third variety that I'm just about to try out that is supposed to be somewhat heat tolerant. Guess I'll see in the coming warmer months. Bok Choi is turning out to be one of my favorite inter crops for raft production.