Calcium or Phosphorus?

[OzbudboY]

I have this issue always come up at the same time, in weeks 3-5 of bloom. I always thought it was a calcium deficiency. Can anyone confirm this? Im using AN pH perfect in dwc. Advanced Nutients say not to ad any other products with it so im not sure how i can add more calcium when it says not to, i dont want to screw it all up.

 

[Emilya Green]

where is this damage on the plant? part of the diagnosis of this will be a careful analysis as to whether this is happening in the old lower growth, middle of the plant, top of the plant or all over.

you say that this consistently happens weeks 3-5... what happens then? Does it continue to get worse or go away or just become a non issue?

this sort of issue is why I don't like systems like AN has, where they claim a one size fits all sort of strategy. Not all pot is the same, not all growers are the same, not all soils are the same, and no one has the same exact environmental conditions. I can not wrap my head around a claim that the same set of nutes in the same proportions will work for Aunt Susie down the street growing under a couple of cfls, and at the same time be fine for me with my crazy bright lights and ridiculous airflow. Then, if that disparity isn't enough, there are hundreds of different varieties of pot, some needing lots of nutes, others very timid when it comes to them. How is it that one set of rules is supposed to work in all cases? It must be a pretty good system that they have there though, because lots of people like the stuff, and it isn't exactly cheap.

I agree that your deficiency looks like calcium is lacking and if these were tomato plants I would predict some black dot disease on your fruit. Whether you should adjust for it is the question, and I think the answer to that is in the answer to my previous question... in cannabis, does it resolve itself later, when other AN nutrients are brought into the mix... or has it become a progressively worse problem in these previous grows? If the latter, despite their warnings not to, I would try supplementing lightly with a good ready to use calcium source.

 

[OzbudboY]

I first noticed the damage towards the middle/bottom on one of the largest leaves, then more appeared around the mid level and now a week or 2 later a very little on the upper half of the plant.
Its hard to tell if it gets better at all, it seems to just slowly get worse until i harvest.

Thank you

 

[Emilya Green]

I first noticed the damage towards the middle/bottom on one of the largest leaves, then more appeared around the mid level and now a week or 2 later a very little on the upper half of the plant.
Its hard to tell if it gets better at all, it seems to just slowly get worse until i harvest.

Thank you

This makes sense and confirms the diagnosis. Calcium is semi-mobile in the plant but generally tends to stay where it is put. This makes it look like it is affecting the entire plant, and will tend to center the damage on areas that are actively growing... leaves that are getting a lot of light, etc.

Logically, the existence of this deficiency proves that AN is not supplying everything that is needed in your particular situation. This is not surprising, as there could be multiple reasons why the Ca is not available to the plant... pH, something else out of proportion blocking it, etc...

My suggestion is that you identify the cause and the solution with an experiment. Take one plant, and start giving it an additional calmag+ supplement along with your nutes. I would also check the pH of the water you give it between nutes, and the actual pH of the nutes/water combination that you use... and again, despite what AN claims about not having to adjust, if your ph was much lower than 6.2, I would adjust it. Calcium simply can't be uptaken at a lower pH than that. If your plain water is out of the range of 6.2-7.0... I would adjust it too. See if this one plant responds to the treatment, and then you will have your answer.

 

[OzbudboY]

I'm doing hydro btw, so i think my pH is too high at 6.2 but i thiunk that is where AN say it should be...I'm going to add the cal mag to one plant like you suggested and see what happens thanks.

 

[Emilya Green]

I'm doing hydro btw, so i think my pH is too high at 6.2 but i thiunk that is where AN say it should be...I'm going to add the cal mag to one plant like you suggested and see what happens thanks.

In hydro, calcium is best absorbed by the roots in the 6.2 - 6.5 pH range and in hydro, it's generally recommended to keep the pH between 5.5 - 6.5, but calcium specifically tends to be best absorbed above 6.2)


After a calcium deficiency is cleared up, the problem (brown spots and unhealthy new leaves) will stop appearing on new growth, usually within a week. Leaves which have been damaged will probably not recover or turn green, so you want to pay attention to new growth for signs of recovery.