Saturday, January 22, 2011

Is Molasses an Iron Chelator?

Aquaponics systems are deficient in one essential thing, and that is iron. As anyone in AP will tell you, it is a metal you must add to your system periodically. Yellow leaves on your plants are usually a good indication that some sort of nutrient deficiency is occurring. Since iron is the one substance AP systems do not naturally contain, and because it has such a tight PH absorption window, it is usually the culprit.

For most people, adding iron is quite simple. Chelated iron is available in most countries at nurseries or from hydroponics suppliers. For most home systems, the amount to add ranges in the teaspoon-measurements range every few months, so it goes a long way.

Chelated iron is simply iron that is loosely bound to a chelating agent, which makes it more soluble and absorbent by cell walls. Commercially available chelated iron for agricultural applications, often uses ethylenediaminetetraacetate (EDTA) as the chelating agent. Chelated iron for human use, marketed as a dietary supplement, often uses an amino acid as the chelating agent.

The reason chelated iron is important is because free-floating iron is difficult for plant cells to absorb, though not impossible. If it is attached to an amino acid or other chelating agent, plant cell walls absorb it readily. Once inside, the chelating agent and iron atom disassociate and the iron can be used for cellular processes. It is especially important for the formation of chlorophyl (itself a chelate), which is responsible for photosynthesis and gives plants their green color. As for how iron is absorbed in nature, or chelated in nature, I do not know - any plant biologists, please chime in!

Some people, myself included, have rusty pieces of metal somewhere in their systems, constantly introducing some iron into the system all the time. I have a rusty chain hung over my tank wall dipped in the water, and I've buried several rusty nails in my grow beds.

If my PH were the perfect match for the iron absorption profiles and needs of all my plants, this should theoretically work. But as Yogi Berra once said, "In theory there is no difference between theory and practice. In practice there is."

The fact of the matter is that my spinach has suddenly turned a really bad yellow. So has one of my oregano plants, but to a much lesser extent. The strange thing is, everything else looks great. All my tomatoes are thriving, blooms coming out everywhere. The cuke plant must have tripled in size since last week. Everything else - all the herbs, lettuce, even the onion and radish which I didn't expect to do well, are doing great or at least look healthy.

So why just the spinach, and to a lesser degree, the oregano? I remember being told spinach is good for you because "it contains lots of iron". If that is true, I suppose it must need lots of iron as well. I'm just speculating, but that would make sense, wouldn't it?

My problem is I cannot find chelated iron anywhere around here. And despite the iron added by my rusty friends, there is apparently no natural chelator in the system to help get it into plant cell walls.

What I did find out, however, is that molasses, the sugar-cane extract, is supposedly a good iron chelator. That is according to this and this.

It is also supposed to itself contain a lot of iron, without any need to add it. I have no idea if this is true, but I am willing to try.

So, last night I sprayed some molasses on all my plants. I diluted it with water a bit. The reason I had some around is because I had once heard it works as a bug repellant. The sweet smell apparently is not liked by many bugs. I actually sprayed it back when I first started 4 months ago, so who knows, maybe I inadvertently added a chelating agent and possibly chelated iron to my system back then.

This morning, noticing the spinach plants were still quite yellow, I mixed some molasses with water (1:9 ratio) and poured it into a small bucket that had rusty nails and even a nice little pile of "rust dust" at the bottom. I am going to let that soak the rest of the day and apply some tonight and the rest tomorrow morning.

Will report back here with whatever the results are.

Tuesday, January 11, 2011

New Piping and Plantings

I forgot to mention in my last update that back in December, I ripped out all my 1/2" PVC piping and replaced it with 1" black irrigation piping. The difference in flow is fantastic. I think this is crucial due to the CHOP MARK II configuration I'm using. Since in this system, part of the water is always returned to the tank before going through grow beds, you need to move more water than you would in a "traditional" system in order to move the same amount of water-dissolved nutrients and fish waste through all the beds and any filters you may have.

When I had 1/2" PVC, the flow into the tank hardly made a splash. And that was with two 500-GPH pumps running simultaneously. Now the flow is fantastic. I haven't measured it yet (and didn't then), but suffice to say it disturbs the water plenty. If you think pump power is all that matters, think again. You'll get much more flow out of the same pump with a larger diameter pipe.

I did this the day before taking off for a two-week vacation, and was pleased to find the water crystal clear upon my return (yes, I do have someone around who checks on the system).

There is not a lot to update right now. I am waiting for a Matala filter system so that I can install some floating raft beds. Turns out my order (placed in early December) was lost and so I just reordered. I considered making my own filter system, but after checking out Matala's materials and their own purpose-built filter box for the filters, decided the cost-value of designing my own wasn't worth it. I'm getting the basic model, without the UV light. That's only necessary for aquaculture-only systems and don't think the bacteria would enjoy the UV light very much.

In the meantime, this weekend I removed all the basil plants in grow bed #1 and replaced them with lettuce and cabbage. The basil was ready to go and the only reason I ever planted as much as I did is because at the time I had to plant something and that's all I had. It will be interesting to see how the lettuce and cabbage grow in the gravel grow beds and then see how they do in the floating raft system.

Here's a video of the first basil plant coming out. I was impressed by the root system.

video


And here are some pics.


Purple Basil in Grow Bed #1


Me next to Grow Bed #2 (herbs, spices and lots of tomatoes coming up)

Me next to Grow Bed #1

This video is just a quick update on what I've been doing:

video


New 1" irrigation piping, and sump in background (note clarity of water)


Fish Tank. I know, the fish weren't cooperating, so they are not in the picture. But, you can clearly see the air diffusor disk at the bottom. This tank is 70cm tall (27") and the bottom and sides are a dull grey. If they were white, you'd really be impressed. :)

Tuesday, January 4, 2011

Quick Update

Finally got back to the farm today after two weeks away. The plants have really taken off and look great. The basil below is the largest I've ever seen and I've grown plenty of it over the years to know these are large basil plants.



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Here is the other grow bed with a variety of spices and now several tomato plants along the back. The tomato plants are all flowering so I should have some fresh pickings soon.




Not so impressive are my lettuces and especially the spinach.

I did get my hands on what I am told are tropicalized lettuce, cabbage and cucumber seeds, which have germinated (below). I will probably plant some this week and the rest when I get a floating-raft bed set up.


The fish look great and the tank water is crystal clear. PH is stable at 6.6. I'll probably go to once-per-week measurements on all variables now that the system has stablized. My fingerlings are now considerably larger - will get pictures soon. I should probably move them to the large tank soon as the sump does not have any emergency back-up pump installed.