Early Phosphorus or Calcium Deficiency? Or Phosphorus Lockout?

[Kazman420]

Problem: Brown/Rust colored spotting resembling burn marks.

Medium: 70% Canna Coco Professional Plus (Brick) / 30% Perlite in a 5 Gallon pot. (3.75 'real' Gallons) [I did not wash/buffer the coco].

Feed: General Hydroponics Flora Series - 6ml Micro / 9ml Bloom + 2.5ml TPS CalMag OAC [Per Gallon]. Manually Feeding 2x Day @ 5.8 pH and 375ppm [.5 Scale] (5-0-1 Micro, 0-5-4 Bloom, 0-0-0 CalMag).

Water: Distilled. Fertigating to 20~30% runoff.

Strain/Age: Mephisto - Forum Stomper @ 39 Days

Light: 400w HPS @ 12 inches. 20/4.

Climate: 55~60% RH / 81° Under Lights / 78° Leaf Temp

Additional Info: I first noticed the problem a couple of days ago on the two smaller fan leaves in the picture below. I started researching but didn't want to make any changes right away since I had recently switched over to the 6/9ml Micro/Bloom on Day 30. Previously I was using 1:1:1 (Micro:Bloom:Gro) for Veg. Today I noticed the larger fan leaf is starting to exhibit early symptoms.

It's also worth noting that I didn't use any CalMag for the first ~12 days or so, until the plants starting developing a fairly obvious Magnesium deficiency. I have been using it since.

Initially I was thinking Phosphorous or Calcium deficiency, but Calcium doesn't make sense since Canna Coco Bricks are supposed to be buffered and there is plenty between the Flora Micro and TPS CalMag. (Unless the Coco is stealing all of it). I'm actually starting to worry there is too much Calcium and it's locking out the Phosphorus.

 

[namvet25]

Your light might be a little close causing heat stress. Do not follow recomended dose on bottle but go half strength and and add cal/mag at 5ml per gal and feed every other week

 

[Kazman420]

Your light might be a little close causing heat stress. Do not follow recomended dose on bottle but go half strength and and add cal/mag at 5ml per gal and feed every other week

Thanks for the reply @namvet25!

I raised the lights to 15 inches. I'll recheck the temperature in a couple hours when I fertigate. It never occurred to me that it could be heat from the light. Weird though since there is a lot of leaves higher up that aren't burned. In fact the middle of the plant where those leaves are is significantly lower than the rest of the canopy.

I don't follow the bottle, I'm used Head's formula, which is a modified Lucas formula. I dilute down to 375ppm (.5 Scale). That's a little less than half as the 6/9ml of Micro/Bloom is about 600ppm. I've tried pushing 400ppm but the girls don't like it.

5ml of CalMag is twice as much as I am currently using. I know coco can do weird things with certain elements and requires additional Calcium and Magnesium. I was worried that I had to much Calcium in there and it was locking out the Phosphorus. I'm guessing there is no (easy) way to check for that and you just have to see how the plant reacts?

 

[tronN00dles]

I'm not sure about the Head's/Lucas formula stuff, but why not follow the actual feedchart straight from GH? It has changed dramatically in the past couple of years, and is now better suited for autos IMHO. It's a more "balanced" formula that is better for scaling down to auto-level ppm's. I notice the formula you're using is modified and doesn't include FloraGro?

Have you seen the new GH feedcharts straight from the manufacturer? If not, here's the lo-down: the "old" GH charts were broken out into "Recirculating" and "Drain-to-Waste", and you could add the 'extras' willy-nilly, however, this might throw off N-P-K's at those lower ppm's autos prefer. The new feedcharts are offered in 3-, 6- and 10-part formulas, which are meant to be used-as is in their entirety. Only the 6- and 10-part contain Cal-Mag, so these would be better suited for coco. Anyway, the formulas are now broken out by "light, medium and aggressive". For autos, I typically follow the 6 or 10-part "light" series, and scale down to ~500ppm or so, depending on the strain.

Here's the new and improved charts: https://generalhydroponics.com/resources/floraseries-feedcharts/

-tronN00dles

 

[Kazman420]

I'm not sure about the Head's/Lucas formula stuff, but why not follow the actual feedchart straight from GH? It has changed dramatically in the past couple of years, and is now better suited for autos IMHO. It's a more "balanced" formula that is better for scaling down to auto-level ppm's. I notice the formula you're using is modified and doesn't include FloraGro?

Have you seen the new GH feedcharts straight from the manufacturer? If not, here's the lo-down: the "old" GH charts were broken out into "Recirculating" and "Drain-to-Waste", and you could add the 'extras' willy-nilly, however, this might throw off N-P-K's at those lower ppm's autos prefer. The new feedcharts are offered in 3-, 6- and 10-part formulas, which are meant to be used-as is in their entirety. Only the 6- and 10-part contain Cal-Mag, so these would be better suited for coco. Anyway, the formulas are now broken out by "light, medium and aggressive". For autos, I typically follow the 6 or 10-part "light" series, and scale down to ~500ppm or so, depending on the strain.

Here's the new and improved charts: https://generalhydroponics.com/resources/floraseries-feedcharts/

-tronN00dles

Hi tronN00dles, thanks for linking those charts!

I hadn't noticed GH had a chart based on growth phase. That's pretty neat! I'm going to have to look into these. The Lucas/Head foruma is fairly popular and works 'as is' with Autoflowers in Coco (with the addition of CalMag). That's why I had initially picked it. The lack of Flora Gro is intentional. Somebody worked out that you get everything you need from just the Micro and Bloom. But it's best if only used during Flowering.

 

[MassMom]

I'm not sure about the Head's/Lucas formula stuff, but why not follow the actual feedchart straight from GH? It has changed dramatically in the past couple of years, and is now better suited for autos IMHO. It's a more "balanced" formula that is better for scaling down to auto-level ppm's. I notice the formula you're using is modified and doesn't include FloraGro?

Have you seen the new GH feedcharts straight from the manufacturer? If not, here's the lo-down: the "old" GH charts were broken out into "Recirculating" and "Drain-to-Waste", and you could add the 'extras' willy-nilly, however, this might throw off N-P-K's at those lower ppm's autos prefer. The new feedcharts are offered in 3-, 6- and 10-part formulas, which are meant to be used-as is in their entirety. Only the 6- and 10-part contain Cal-Mag, so these would be better suited for coco. Anyway, the formulas are now broken out by "light, medium and aggressive". For autos, I typically follow the 6 or 10-part "light" series, and scale down to ~500ppm or so, depending on the strain.

Here's the new and improved charts: https://generalhydroponics.com/resources/floraseries-feedcharts/

-tronN00dles

The new charts say 1.9 or 3.8 or 4.7ml...how in gods name do you measure that? I have enough trouble measuring to the line with my syringes, never mind "points"! Can you just "round up" and dilute down if the ppm's come out a little high?

 

[tronN00dles]

The new charts say 1.9 or 3.8 or 4.7ml...how in gods name do you measure that? I have enough trouble measuring to the line with my syringes, never mind "points"! Can you just "round up" and dilute down if the ppm's come out a little high?

Yeah they're annoyingly precise. My guess is the older charts were all based on fairly round numbers per gallon, but the to-metric conversions meant dividing everything by 3.79 rather than 4.0, so now we get this decimal point. Personally, I use a combination of bigger and smaller pipettes/syringes. I have some 3mL pipettes that are accurate to 0.5mL and I eyeball the in-betweens. I also usually assume there 20-25 drops per mL, i.e., 2 drops per 0.1mL or so.

That being said, the 1.9, 3.8 etc. are often nice ratios like 1:2, so you could just follow the ratio like that and scale up your water appropriately too. If that makes sense. Anyhow, I'm sure if it calls for 1.9mL and you give it 2.0mL, it won't turn to poison

It makes me think of nute recipes that call for "a half teaspoon" per gallon. I bet if you measured up 100 different half-teaspoons they'd often find themselves within a few points of 2.5mL. No way they're getting exact every time.

-tron

 

[Kazman420]

Personally, I use a combination of bigger and smaller pipettes/syringes. I have some 3mL pipettes that are accurate to 0.5mL and I eyeball the in-betweens.

This is exactly what I do. A 1ml and 3ml plastic pipette gets me close enough to any dose. I keep one of each attached to each bottle of nutes by a rubber band, hehe. Surprisingly my nute mix comes out to within ~5% ppm each time. Sadly the only way to buy them on Amazon was in a package of 100, so now I've got a lifetime supply of them.