Hydroponic Green Beans Question

11 years ago

last modified: 11 years ago

This is my second attempt at growing green beans hydroponically. Using the Kratky method except I do have a bubbler for more air. The issue I'm having is this odd leaf bleaching and discoloration.

Air Temp is 72, water temp is usually between 65 and 68. PH is 6.23 and the ppm is 350 this time. There are a total of 4 plants and all of them are exhibiting this to some degree. From reading it sounded like a mold or mildew, but its not powdery at all and it didn't seem to look like any of the pictures I saw.

Does anyone have any idea what might be causing this? Or what I can do to stop it?

Featured Answer

hydroveggiegrow

11 years ago

That's make sense if you're seeing some underdeveloped roots since a calcium deficiency can cause that. And with underdeveloped roots comes stunting of growth. And stunting of growth will cause lower transpiration rates which will cause less calcium uptake. It's a vicious cycle.

Calcium travels into the plant with water uptake and has to be in high concentrations in your nute solution in order to maximize that uptake. Nearly all commercial nutes I've seen are low in calcium. For the most part that's because if people are using them with soil or hydro and tap water, which usually contains a lot of calcium, they assume there is another calcium source. Somewhat the same thing with magnesium. Which is why many manufacturers specifically state that if you're using RO then you should use a cal-mag as well, and of course they make one! How convenient. I figure out the PPMs and have my own formula that increases Ca to almost around my N levels and Mg to at least 80% of K. Once I tweaked my ratios I haven't had any calcium or magnesium issues at all and overall better and faster growth.

But figuring all that out for most with dilution rates and whatnot is daunting so I would start by doubling your dose of cal-mag and get some air, if you don't already, blowing on those plants to increase transpiration (water uptake). Or you could use your cal-mag as a foliar spray...or both for that matter.

Dyna-Gro makes good products, I use a few, but it's weird that they have so much phosphorous in that mix. But having said that, it's not likely you would ever get a phosphorous toxicity and that would usually just cause some issues with some of the metals.

I'd give that a go. This is all assuming that you're changing your solution at the appropriate times and maintaining pH and whatnot. Too low of pH can cause Ca problems as well as some others.

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Comments (7)

hydroveggiegrow
11 years ago
If I had to hazard a guess I'd say calcium deficiency. I've seen something similar on my tomato plants before and it was calcium related. It's not only the necrotic spots but I can see some signs of it on other leaves - that slight crinkling and some distortion on some leaf margins.

What nutes are you using? How much Ca and NPK? RO water or tap?
Joshua Terry
Original Author
11 years ago
I've been using Dyna Grow which is 7-9-5 and adding Mag-Cal + for the calcium, magnesium, and iron. I only added about half the recommended Mag-Cal though since they were so young.

I normally use Rain Water that I harvest into barrels for the water.

I confirmed its definitely not White Powder Mold or Mildew. We have a bush outside with it and its nothing like it. The spots are completely devoid of color almost like its been bleached. It doesn't seem like its spreading to the new leaves yet.

One of the 4 plants seems oddly stunted as if frozen in time. I started all of them at the same time, but 1 of them seems like it just stopped growing after 2 leaves. It looks fine and healthy except that it appears about 2 weeks behind the others and has no visible roots from the bottom of the cup.
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Joshua Terry
Original Author
11 years ago
I did not realize you could use Cal-Mag as a foliar spray! I haven't used any sprays yet as I wasn't quite sure of their effectiveness. I will have to try this.

I will say that since I have increased the amount of Cal-Mag in the solution they do not seem to be getting worse. I had hesitated adding too much initial as I had read that a common beginners mistake is too add too much.
hydroveggiegrow
11 years ago
The damage on the leaves that's already there won't go away so just pay attention to new growth and growth that's undamaged and keep an eye on it.

Tell tale signs of calcium deficiency are "j-hooked" leaf tip, basically tips that curve left or right, distorted new growth, or cupped leaves (up or down, but I most the time see up).

I wouldn't worry about giving it too much cal-mag. I've never seen a calcium or magnesium toxicity in any of my plants and run high levels compared to most although some elements are antagonistic and will interfere with the uptake of others but generally nothing to worry about with Ca and Mg.

Give me an update after awhile if you don't mind. I'd like to know how it's working out.
Joshua Terry thanked hydroveggiegrow
Joshua Terry
Original Author
11 years ago
Your advice made a tremendous difference! I started adding more CalMag to the Nutrient solution as well as creating a foliar spray which I've been using on Beans, Tomatoes, and Peppers. I've seen improvement in everything since began using it.

Here's a picture of one Green Bean plants now. You can still see the one damaged leaf but all of the new growth appears very healthy with a good deep color.

Thank you very much for this advice, it has really helped!
hydroveggiegrow
11 years ago
That's great to hear. Glad I could help.