Question regarding Ca uptake in early flower and VPD

[ButterflyEffect]

So, this is something that's been on my mind for a while now.

What is the recommended VPD for early stretch/flower? The suggested range is 1-1.4. That's a fairly wide range, IMO. Assuming a static temp of 80F/27C, which is where my rooms are, a VPD of 1.0 puts me at 65% and a VPD of 1.4 puts me at 55%.

That all said, I was under the assumption that I'd at want to have the VPD be lower(higher humidity) in stretch at least, and then adjust more toward a VPD of 1.4 by mid-flower. What makes me rethink all of this is I know I'm seeing mild Ca defs by day 10, or so. I'm seeing not only the tell-tale signs on a few lower leaves but also fans snapping off far too easily and even some branches snap far easier than they should. It's making me think that the low VPD is reducing transpiration and thus reducing the flow of water through the plant, which naturally lowers Ca uptake.

Am I on to something here or chasing whims?

One more thing to add. I'm using stacked bare 315CMH lamps vertically. PPFD is about 7-800.

 

[Piff_cat]

I've found foliar of dolomite lime kelp and humic acid at 7 ph does wonders for plant in this stage. Calcium is the limiting factor for new vegetative growth being non mobile. Altho deficiency should show first In New growth. Taking it a step further nano drilled calcium carbonate applied foliar underneath leaf can now be uptake thru stomata directly. This form of calcium is what plant turns co2 into as intermediary actually providing co2 supplement in this way!

 

[ButterflyEffect]

I've found foliar of dolomite lime kelp and humic acid at 7 ph does wonders for plant in this stage. Calcium is the limiting factor for new vegetative growth being non mobile. Altho deficiency should show first In New growth. Taking it a step further nano drilled calcium carbonate applied foliar underneath leaf can now be uptake thru stomata directly. This form of calcium is what plant turns co2 into as intermediary actually providing co2 supplement in this way!

Huh. It was my understanding that Ca simply doesn't uptake via foliar. From what I read it only moves through the plant when you water.

 

[f-e]

I think bill does a foliar to help the initial transition. I tried it, but it just left white dust everywhere lol

If the only signs are snapping, are you sure that's a Ca problem? It's not an association I have made before. I thought it K that caused otherwise good looking leaves to break away easily.

 

[jackspratt61]

Cu is the culprit for brittleness.

 

[Piff_cat]

heres an article for ya. calcium is highly avilable in foliar. kelp contains tons of micronutrients hromones and just general goodness for the ladies. a 2 to 1 humic acid mixture greatly improves the action. now it is best absorbed by stomata underneath leaves but recent research has verified it also absorbed thru cuticle. when i grew in coco i had constant calcium magnesium problems due to cation exchange. calcium foliar is a miracle worker. altho i switched to rockwool i still use the foliar. cant go wrong
https://www.grozine.com/2014/07/16/foliar-feeding-with-calcium-chloride/

 

[ButterflyEffect]

I think bill does a foliar to help the initial transition. I tried it, but it just left white dust everywhere lol

If the only signs are snapping, are you sure that's a Ca problem? It's not an association I have made before. I thought it K that caused otherwise good looking leaves to break away easily.

Hello old friend!

Honestly, I'm not sure. I'm trying to become much better at diagnosing events like these. I'm getting better but still I need improvement.

One other thing I've noticed is I was ramping up the ratio of CalNit to Part A(Jacks Hydro 5-12-26) to .72 instead of .67 and I was adding about 2ml/G of CalMag. The issue really manifested itself after a recent set that I transplanted. They were all looking droopy and sad with red striations forming on the stems at the top. Classic Mg def. I then realized that Ca competes with Mg for uptake and I immediately backed off on the CalMag, dialed my ratio back to .67, and did an Epsom foliar for 2 days. Now things are looking great with those plants.

The long and short of it is I think I'm my own worst enemy yet again! It's likely I was locking something else out from too much Ca, unless of course, it was just the Mg, but I know that excess Ca messes with quite a few things.

 

[ButterflyEffect]

Cu is the culprit for brittleness.

I'll have to look into what locks out Cu. If you read my past post you'll see that I was likely inducing deficiencies with excess Ca. I'm sure an occasional Micro foliar wouldn't hurt either.

 

[ButterflyEffect]

heres an article for ya. calcium is highly avilable in foliar. kelp contains tons of micronutrients hromones and just general goodness for the ladies. a 2 to 1 humic acid mixture greatly improves the action. now it is best absorbed by stomata underneath leaves but recent research has verified it also absorbed thru cuticle. when i grew in coco i had constant calcium magnesium problems due to cation exchange. calcium foliar is a miracle worker. altho i switched to rockwool i still use the foliar. cant go wrong
https://www.grozine.com/2014/07/16/foliar-feeding-with-calcium-chloride/

Thanks Piff! I'll check that out as a lot of the reading I had done stated that Ca simply doesn't absorb well with foliar, but that didn't mention Ca Chloride so that might be the difference.

 

[f-e]

Calcium annoys almost everything, but not Cu.

While double checking my K idea, The article said the early sign was red stripes up the stem. They spoke of K carrying NO3 around, which was the actual problem.

I have seen vertical red stripes blamed on many things. I recently had them, and it was my Ca treated plant that come good, not the Mg treated one. I realise it's not what we wanted to hear, but it is what it is. Red stripes are most commonly related to P K Ca and Mg. That's not a full list though. I believe Mg will start on the petioles and then the stem. Though red petioles may be just light exposure, so the stem then getting stripes, isn't related. We want red encircling the petiole, or concentrated below it, to see it as Mg.

 

[jackspratt61]

These nutrient interactions aren't linear. Notice BF problems disappear as he brings his ca/mg ratios in line. Being in a hempy won't allow for withholding mg like in a mix. Mg aids P uptake. P aids cu.

 

[Piff_cat]

low rootzone temp creates a phosphorous deficiency raidply especially after transplant transition to flower. it is a common problem with leds since they put off very little infrared heat. red stems are biggest sign but necrosis on lower leaves as well. reduction of transpiration caused by low temps many problems. in my experience its very rare for a nutrient deficiency be caused by lack of nutrient in feed. more likely its enviorment , ph, sodium, or too much of another nutrient causing lockout. low ph or lack of run off causes many issues

 

[jackspratt61]

I'll have to look into what locks out Cu. If you read my past post you'll see that I was likely inducing deficiencies with excess Ca. I'm sure an occasional Micro foliar wouldn't hurt either.

Be careful using some of these fertilizers that contain certain chelators for foliar. They can actually pull other elements from the leaves.
How long have you been using hempys?

 

[ButterflyEffect]

Calcium annoys almost everything, but not Cu.

While double checking my K idea, The article said the early sign was red stripes up the stem. They spoke of K carrying NO3 around, which was the actual problem.

I have seen vertical red stripes blamed on many things. I recently had them, and it was my Ca treated plant that come good, not the Mg treated one. I realise it's not what we wanted to hear, but it is what it is. Red stripes are most commonly related to P K Ca and Mg. That's not a full list though. I believe Mg will start on the petioles and then the stem. Though red petioles may be just light exposure, so the stem then getting stripes, isn't related. We want red encircling the petiole, or concentrated below it, to see it as Mg.

Ca doesn't antagonize Cu, but N does. If you recall I upped my ratio of CalNit from .67 to .72 and also added CalMag(I was trying to buffer my water) both of which have ample NO3. The red did tart on the petioles, fyi.

 

[ButterflyEffect]

These nutrient interactions aren't linear. Notice BF problems disappear as he brings his ca/mg ratios in line. Being in a hempy won't allow for withholding mg like in a mix. Mg aids P uptake. P aids cu.

And of course, my ratios were tweaked to provide more Ca. I really need to keep to the basics more.

What do you mean about the hempy not allowing Mg to be withheld? I gotta say, I think the hempys cause more problems than I like. I wish I could move away from them but I collect rainwater and I need to be wary of running out of water so a full-blown DTW isn't in the cards right now. The way I have my res pumps set for fertigation keeps the pots on the dry side(3 feeds/day) with no runoff, then I flush weekly. This has given me the best balance of water conservation and limiting media buildup. I also have 3 1/2" holes for assured drainage and I've recently cut the vermiculite down considerably to keep the overall CEC lower to avoid excess salt buildup.

 

[ButterflyEffect]

low rootzone temp creates a phosphorous deficiency raidply especially after transplant transition to flower. it is a common problem with leds since they put off very little infrared heat. red stems are biggest sign but necrosis on lower leaves as well. reduction of transpiration caused by low temps many problems. in my experience its very rare for a nutrient deficiency be caused by lack of nutrient in feed. more likely its enviorment , ph, sodium, or too much of another nutrient causing lockout. low ph or lack of run off causes many issues

It's not rootzone temps. Environment is fully dialed. AC, Heat, Dehuey and a line-pressure mister are all controlled by home-built arduino controllers. Extractor fan cycles the room air every 15 mins.

I agree with your point on what generally causes deficiencies. I guess I was wondering whether having a low VPD, which naturally would decrease transpiration, could be contributing to a Ca def since it only gets taken up when the plant is transpiring. I found it odd considering that the VPD when I put them in flower is the same from the veg room they just came from.

 

[ButterflyEffect]

Be careful using some of these fertilizers that contain certain chelators for foliar. They can actually pull other elements from the leaves.
How long have you been using hempys?

The only foliars that I use are a Rhizo for anything in early to mid veg, Epsom occasionally as needed and Vitazyme, which I do currently twice a month. All have a touch of Mr Fulvic in them. I do have a Micro(It's just Jacks MOST) foliar mixed, and MKP, as well, but I don't use them with any regularity. They just kind of hang out if needed. I might use the Micro if I see the new growth coming in too light of a green.

I've been in perlite/vermiculite hempys for about 5 years now. I'd love to move away from them, as my gut tells me that they were never meant for multiple daily feeds. Not to mention that the plants go into flower at 40" and max out at about 48", all rootbound in a 1G container, hence the 3 feeds per day. That's why I recently cut the vermiculite down again. It's now a 12:1 ratio. Significantly less than the 4:1 that's typically recommended. Having an unpredictable and finite water supply has dictated this media decision, btw.

 

[jackspratt61]

And of course, my ratios were tweaked to provide more Ca. I really need to keep to the basics more.

What do you mean about the hempy not allowing Mg to be withheld? I gotta say, I think the hempys cause more problems than I like. I wish I could move away from them but I collect rainwater and I need to be wary of running out of water so a full-blown DTW isn't in the cards right now. The way I have my res pumps set for fertigation keeps the pots on the dry side(3 feeds/day) with no runoff, then I flush weekly. This has given me the best balance of water conservation and limiting media buildup. I also have 3 1/2" holes for assured drainage and I've recently cut the vermiculite down considerably to keep the overall CEC lower to avoid excess salt buildup.

Many mixes are loaded with mg and the plant can, once rooted in well,'scavenge' for that mg quite effectively. I've grown in peat and coco with only slight addition of mg to the mix or even just a few light mg foliars.

 

[ButterflyEffect]

Many mixes are loaded with mg and the plant can, once rooted in well,'scavenge' for that mg quite effectively. I've grown in peat and coco with only slight addition of mg to the mix or even just a few light mg foliars.

The Jacks I use is around 7% Mg. I used to add in extra when I started using it, you know 3-2-1? It gave me Ca issues. Now I mix about 25-30%$ of my tanks with well water for the buffering ability and the extra supply. No more added Mg and no more CalMag. Things are looking very good. Time will tell on whether I can get the buildup under control. It would at least save water.

 

[Piff_cat]

the way i look at humidity is a shield. it allows you to run the temp you want high enough so that transpiration is peak and stomata is open to ideal amount. lowering that shield increases transpiration at first but once it crosses over to the dark side the stomatas close as an emergency intervention to slow water escaping.in turn stops calcium from being mobile but also can lockout other nutrients due to cascade effect on taking up too much too fast. thats where leaf surface temp really comes into play. similar to chuggin a milkshake leads to stomac ache.

its hedgin your bets compared to how often your able to refresh roots with feed. so there are inhibitive dangerous zones at too dry or too moist and then a sweet spot zone which you can choose either aggressive(less) or safe(high) rh levels. it is also strain dependent to a point. lowland plants seem to like media constantly moist but not soaked or dry and a higher comparative humidity. highland plants seem to want the rootzone moisture to swing between extremes. they also like a lower humidity overall. while further dryouts will increase resin content, but that is counterproductive if the dryness is detrimental to primary growth. secondary metabolites eventually run counter to plant health since they are designed to combat biotic dangers.

ive never used hempy but runoff readings for ec and ph are great ways to determine where a problem starts when compared to reservoir levels