Magacrop Deficiency Issue?

[Jerry Tyson]

Hi Everyone, I've spent a lot of time reading posts and everyone on here is amazing. So many talented growers with years of experience. I started my first grow. After reading through a lot of posts I decided MegaCrop (2020 version) would be the easiest and most straight forward approach for a new inexperienced grower like myself. I'm growing Cinderella XX from Brother's Grimm Seeds in a 4x4 tent with a quantum board LED light. It was off to what I thought was a great start. Day 37 picture shows the plants they seem healthy and happy. I have not been PH'ing my water as I've read with MegaCrop's chelated formula with low alkalinity minimizes PH swings and Promix BX has a buffering agent in it. I started early on at 1G/Gallon and worked my way up to 5G/gallon as they have gotten larger and shifted up to 5 gallon fabric pots (their final size). Around day 41 they started to show some leaf issues and has progressed to what they look like now (day 45). My initial thought was the bright LED light and RO water along with the way the leaves are looking make me think I may have a Calcium Magnesium deficiency. The seed package does say the plant likes extra cal/mag. I started adding 3 ml/gallon Bontanicare Cal/Mag Plus and in the most recently watering, I upped it to 5ml/gallon (the high range of their suggested). I do know I have a small amount of spider mites, which I am in the process of ordering something to treat that, but I don't suspect this type of leaf damage is solely from that? I've read a lot of posts from some experts on MegaCrop and growing as a whole like @Emilya but unfortunately I'm struggling to recover. Any insight or help anyone has would be very much appreciated. Thanks!

 

[Pennywise]

Let’s see if @MrSauga or @InTheShed might know what’s up.

 

[InTheShed]

Thanks for the shout Penny!

I've read with MegaCrop's chelated formula with low alkalinity minimizes PH swings and Promix BX has a buffering agent in it.

Just to set the record straight, amino chelating the micronutrients in the MegaCrop makes no difference to pH, nor is there any alkalinity in MC that effects pH either. You might be confusing the fact that the alkalinity content (not the pH) of your water can change the pH of the ProMix over time.

In terms of your leaves, I would start with a slurry test of the ProMix and see what it comes back as. A slurry test is when you scoop out some of the dirt at root level (not just off the top) and mix it with distilled water (not RO). Stir it every 15 minutes for at least an hour and then check the pH of the mix.

I usually go with 10g of soil and just enough distilled water to get it into stirrable form, to make a thick slurry.

If it's not 5.8, then the pH of your ProMix has shifted, and if it's far off then that is probably the cause of your leaf issues.

Also, using RO water can result in cal-mag deficiencies as you mentioned. But I'd start by making sure your ProMix is close to factory specs.

 

[Emilya Green]

I suspect that my opinion will not be shared by the others, but I see the common problem with MC that happens when you use outside supplements as well as too much MC. MC comes with a lot of Mg and Ca in the base mix, and the instructions tell us that if we see deficiencies to add more MC. What is not clear is that adding more MC can also cause lockouts of K, since N, Ca and Mg all have negative interactions with K, and with all three of them in excess, it locks out the K. Your problem looks like a K deficiency, but I submit that it is instead a K lockout. Stop the additional calmag and reduce your MC down just a bit, and it is my belief your lockout will go away.

 

[Pennywise]

Thanks Shed.

 

[Pennywise]

Thanks Emily, i see a K definetly. Wasn’t sure about his ph levels though.

 

[PK]

i notice this problem more often now when people are using MC and adding additonal supliments and not rducing the MC. Emilya and the shed got it to the point. Deffinitly a K lockout. Slury mixture is your step one as the shed mentioned. While checking your PH also check your PPM if you happen to have a pen reader. Also, 4.5g per gallon is where the sweet spot is for MC. If you are planning on adding anything else to mix you need to reduce the MC
I would also stop taking any deffected leaves off as it wll just make the other leaves go bad. Once your lockout is fixed then take them away.

 

[Pennywise]

I just don’t see a need to use additives with MC especially when first using it.

 

[PK]

well thats where the problem is becasue the internet is full of content with adding different additives to fix deffeciency and when they add (ex) cal/mag which in this case it will boost the (K) which will overexceed and lockout.

Penny this round im doing nothing but MC however, i would like to find something to give the buds better taste

 

[InTheShed]

Confectioner's sugar! Shows up well in pics too .

 

[Pennywise]

Hahaha water with Dr. Pepper!

 

[Fuzzy Duck]

Seems odd to get K or potassium def in veg...

But in the early days of growers using LEDs most seem to have reported Ca/Mg defs as well & the seed brand mentioned that on the packet !

I'm not sure on what to think about it at present... depends on how long you have been using Ca/Mg supplement as well, this will not automatical make the leafs better again as once damage are more less fceked apart from N def which is to sort out.

At a hunch - lock out, not sure how often you add Ca/Mg supplement which in turn could lead to problems, nutrients are often acidic in nature so over feeding may of caused PH swing as well in the medium leading to lock out...


Mmm test the soil PH which ever way you find best !

If out of sink a heavy flush may be required.


Another question it appears Megacrop is granule nutrient did you get ratio right ?

 

[Jerry Tyson]

Thank you everyone for your quick response! @InTheShed I have a soil sample taken and have it in distilled water stirring every 15 minutes and will follow up with my results as well as PPM @PK1 . I had been running just MC until I started having leaf issues at which point I supplemented with the CalMag but didn't decrease MC. That being sad, at that point I was up to 5g/Gallon which very well may have been to much to @Emilya point. @Fuzzy Duck I took the MC from the larger bag into a mason jar and then weigh out on a 0.01 gram tolerance scale.

 

[EhCndGrower]

I too just use Mega Crop for my nutrients and have had/seen the leaf issue with my past 2-3 grows. I found my issue got better adding the Cal/Mag supplement to my feeding, and watering every other day. I usually could go 3 days before watering my plant but upping my watering seem to really improve my situation. Also helped that I would have more Mega Crop and Cal/Mag to feed their needs too. Always using Pro Mix All Purpose in 7G felt grow bags for my grows

Love MC, even with these little issues with my grows.

 

[Jerry Tyson]

@InTheShed my slurry test shows a PH of 6.4 and 1020 PPM. I will admit the Promix BX bale I got was left over from a friends father from last year and I know the makers of Promix say " A growing medium should be used within nine to twelve months of its manufacturing date to ensure that the pH of the unused growing medium is not too high." Is 6.4 high enough to exert that type of damage by falling out of the ideal absorption range? If so, any way to bring it back in? @EhCndGrower those are interesting observations, especially the watering every other day. Thanks everyone!

 

[InTheShed]

6.4 shows that the pH has drifted up, but I'm not sure it's high enough to cause those kind of issues. I would go with Emilya's suggestion of lowering the MC and cutting the cal-mag, but with a clear-out first. I'd go with 2x the pot size with plain tap water followed by 2 gallons of MC at 4.5g/gallon.

You might also see if you can get your hands on some 20-10-20 powdered fertilizer that isn't all nitrate (like MC) which will lower the pH of the ProMix. I used GrowMore Orchid Fertilizer (with ammoniacal and nitrate N) for three waterings and it dropped my pH by over a point (I was at 7.4 in my old ProMix ). If you go that route, I'd put two gallons through a 5 gallon pot each time so it's completely saturated.

 

[PK]

@InTheShed my slurry test shows a PH of 6.4 and 1020 PPM. I will admit the Promix BX bale I got was left over from a friends father from last year and I know the makers of Promix say " A growing medium should be used within nine to twelve months of its manufacturing date to ensure that the pH of the unused growing medium is not too high." Is 6.4 high enough to exert that type of damage by falling out of the ideal absorption range? If so, any way to bring it back in? @EhCndGrower those are interesting observations, especially the watering every other day. Thanks everyone!

i think you found your prob

 

[InTheShed]

i think you found your prob

If you think that's high enough to create the lockout then the 20-10-20 with ammoniacal N is the way to fix it. Got that info directly from ProMix and it worked for me.

 

[PK]

@InTheShed i thought due to his stage of plant and added MC with 5ml calmag at 1020ppm would be a bit excessive, but you know more then i do and if the promix guys have mentioned it to you and you have tested it then he should perform this to save the plant.

you know i am against flushing most of the times but wouldn't that help in this case instead of buying another additive?

 

[InTheShed]

It's hard to know what deficiencies will show up when with pH drift without some testing, but I'd say the fastest fix is to lower the pH. Flushing and resetting at a lower PPM can take some time to show results, where you can do another slurry test in a week and have your answer on the pH.