Calcium deficiency in flower?

So I’m dumb. I was trying to figure out what was wrong with one of my plants. Originally I thought it was caused by a faulty PH meter, and although replacing it didn’t seem to help, it was still a good idea, but by this point the plant looks terrible. TONS of rust spots everywhere. Luckily there’s less than 3 weeks left but I was just curious how much that will affect the quality and also really hoping it doesn’t just flat out ruin it the harvest.
I’m currently growing in some cheap coco since I couldn’t get something better at the time. I guess double buffering wasn’t enough.

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O.k. do you have calibration solution to calibrate and check your ph meter?

What is the ph coming out of the bottom of the pot what is your runoff ph?

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I do have calibration solution as well as storage solution and I tend to calibrate it before every use just in case. I however do not check the Ph of my run off. I was told it didn’t matter during my first grow and to rly only focus on the ppm of the run off. I use the G.H. flora series and feed at 5.8. the one time i did check my run off though (during my first grow) it was coming out around 5.3.

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The runoff pH is used to determine the pH in the soil, so if it is off then the soil could be locking out nutrients. 5.3 was on the bottom edge of the range.

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Alright, I’ll have to check today when I water them but I feel like according to that chart I should be aiming closer to 6.0? I’ve come across a few different ones so I’m not sure which to go off. But then I guess once I figure out my numbers do I feed with a higher ph if the soil is too low or is it better to flush then feed?

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Agree. 5.8-6 is your target. The best way to get your pH right is feed full strength at the target until it is right and then dilute, not try to move the pH with water and then add. There is no buffering capacity to change the pH in water.

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How about a picture of the plant in natural light? Overall shot and some showing the issue.

Sure, I’m just not great with a camera and also can’t do it in natural light but still better than nothing, maybe.

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So I just fed one of my two plants and the PH of the runoff was 5.1 from feeding at 6.0. That plant isnt the one pictured above but is now starting to show the same signs when the lights came on. But are you saying I should basically be flushing it with full strength feed until the runoff matches?

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Just keep on as you’re doing with waterings and feedings at the high end (6.0 is good) and that will help. Are you using cal mag because you should unless the nutes say you don’t in coco.

What is your feeding/watering cycle? It should be feed/water/feed/water at this point. It gets tough to identify the proximate cause of a problem this late in flower when deficiencies are expected lol.

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I mean, if I know what I’m talking about, I use the Lucas formula just 4-4-8 calmag, micro, bloom. But I personally feed with every watering, basically a manual drain to waste system with about 50% runoff. Though I really only focus on the numbers of very last bit of it, usually about the last cup or so out of a gallon. Probably making a few mistakes there but this is only my second grow so I’m still trying to figure out a system.

I use coco and what I found is it’s best the completely flush every 2 weeks instead of what I was previously flush every 4th week, as coco holds onto the salts in the nutes a lot more than soil, I started doing this on my current grow and it’s turning out to be my best grow so far.

Yeah that’s what I had originally discovered as well. I found myself flushing once every week or 2 as the ppm kept rising but this way the initial runoff is coming out maybe 500 over what I’m feeding but the last bit is only 50-100 over. Though I may have to go back to flushing for my next one just to actually compare.
Either way thank you for all the information. It at least sounds like I shouldn’t worry too much at this point but maybe pay a little more attention the next time around.

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