Magnesium/Calcium?

[thepike1984]

Hello everyone. Hoping to get some help with my latest grow. The 2 strains im doing this time are GHS Hawaiian Snow n also there Lemon Skunk as its some seriously tasty bud. Ill try to give as much information as i can think is necessary.My plants germinated no problem and were doing great for the first few weeks. The Hawaiian Snow leaves started going yellow earlier than the Lemon Skunk. They have since both started to show rust spot on some of the fan leaves. I copied someones Q&A form which i think may be useful for you guys diagnosing my plants. Iv been given some products that a buddy recomended i use but i want to get you guys opinion before i start adding different juice. Ill post some pics of infected leaves and the stuff my mate gave me at the bottome of the post. Please ask if iv missed anything out you guys need to know. Thanks everyone. Best forum out there. You guys should be proud

Strain of Mj?
GHS Hawaiian Snow and Lemon Skunk

From seed or clone?
Seed

Age of plant in question?
6 weeks of veg, 1 day of flower

Medium (Soil, Rockwool, Hydroton etc.)?
Atami Coco Substraite

Container/Pot size?
15 Litres

Feeding schedule?
Lucas formula every 2 days. Been adding Epsom salts the past 2 weeks

When were they last fed/watered?
Yesturday

How are you determining when to feed/water (weight, wilting, etc.)?
Weight of pot n how dry coco looks

Tap/RO/Distilled water?
Tap

Ph of nutrient solution?
plant is fed 5.8 nutrient solution. Run off is about 6.7

Is your Ph equipment properly calibrated?
ph pen calibrated 30 mins before test

Grow room dimensions?
Secret Jardin DR120

Light intensity/Age of bulb/Wattage?
Veg 250w metal halide, aprox 1 year old
Flower 250w HPS, 1 day old

Distance to the canopy?
about 12 inches

Temps?
74-84 degrees

Current air flow (CFM)?
Unfortunately at this present time there is no intake or exhaust fan in the tent. Door of tent open while light on and an oscilating fan blowing more or less directly on plants.

Is there air blowing directly onto plant?
Yes

Relative humidity?
50-60% lights on. Can reach up to 90% lights off

Growing technique (Scrog, Sog, Supercropping etc.)?
Normal

Has plant recently been pruned, clones taken, fimmed or pinched?
No

Pests?
No

 

[BrainSellz]

Feeding schedule?
Lucas formula every 2 days. Been adding Epsom salts the past 2 weeks


Tap/RO/Distilled water?
Tap

Ph before and after adding nutrients?
Before 5.8 After 6.7


Distance to the canopy?
about 12 inches

Temps?
74-84 degrees


Relative humidity?
50-60% lights on. Can reach up to 90% lights off

Hey Pike I see you use the Lucas formula have you tried using the nutes with a different formula?

What are the ppms of your tap water? And I dont know much about cocoa but R/O might be what you want, but like i said i dont really know about cocoa. Tap is usually good for regular soil in most cases.

You might wanna check out what the pH is suppose to be for cocoa as 6.7 seems to be a good ground soil pH, but i dont know if same goes for cocoa.

The temp fluctuation is a little high and 90% humidity is definitely too high, somewhere between 40%-60% humidity is about where you wanna be, I like 50% with lights on and 55% with them off no more than 60% for me though.

Though I cant say these are whats causing your plant problems this will help you avoid some. Have a good one

 

[thepike1984]

Hey Pike I see you use the Lucas formula have you tried using the nutes with a different formula?

What are the ppms of your tap water? And I dont know much about cocoa but R/O might be what you want, but like i said i dont really know about cocoa. Tap is usually good for regular soil in most cases.

You might wanna check out what the pH is suppose to be for cocoa as 6.7 seems to be a good ground soil pH, but i dont know if same goes for cocoa.

The temp fluctuation is a little high and 90% humidity is definitely too high, somewhere between 40%-60% humidity is about where you wanna be, I like 50% with lights on and 55% with them off no more than 60% for me though.

Though I cant say these are whats causing your plant problems this will help you avoid some. Have a good one

Hey thanks for stopping by. Unfortunatly i dont know my ppm's. My Ph is all good for coco. May invest in dehumidifier.

Pike

 

[BrainSellz]

Hey thanks for stopping by. Unfortunatly i dont know my ppm's. My Ph is all good for coco.

Pike

An EC meter is something to invest in for sure. Without knowing the ppms or EC it could make things difficult, imo.

 

[captinknots]

ive been doing coco research to make the switch, so no experience in my answer, but from what ive read, coco sucks up cal and mg. try adding 5ml of cal mg/gal. i dont think epsom has enough cal in it.... my 2cents.

 

[BrainSellz]

. May invest in dehumidifier.

Pike

Some good air exhaust would help also

 

[captinknots]

oh yeah, isnt coco supposed to be in the 5.8ph range? if your adding water frequently and feeding hydro style, keep your ph down. a ph in the 6's is if youve added amendments to your coco and water less often....

 

[thepike1984]

oh yeah, isnt coco supposed to be in the 5.8ph range? if your adding water frequently and feeding hydro style, keep your ph down. a ph in the 6's is if youve added amendments to your coco and water less often....

The ph of my solution is 5.8. Now its in flower im going to gradualy rise it to about 6.3. Defo need to invest in some proper air flow and circulation. An EC meter i also defo need. Thanks for the help so far folks

Pike

 

[thepike1984]

Any more opinions?

 

[captinknots]

apparently to much mg (epsom) will lock out ca. it totally looks like ca lock out or deficiency. what have you done to remedy and what did they look like 2 weeks ago when you started adding epsom? how have they changed? im certainly not a pro but i know for a fact that pic looks like cal def bro.

 

[spurr]

Just curious:

How much Mg are you adding (ppm)? I had used the Lucas formula or a long time, and then using 8 ml FlorNova Bloom that is Lucas formula in one bottle; both in coco and s.peat. It has enough Mg, esp. if you applying Lucas formula each time you water (IMO that's a tad to often with Lucas formula). The Lucas formula is not causing Ca or Mg issues with your plant.


My main guess to your Ca issue:

It's due to the dark period RH, wowzers~!

The short answer:
Drop night RH to ~50%, and try to keep day RH ~60% (considering your day time canopy temps). Get the night RH down and your plants will be able to transpire much better at night, thus allowing a lot more Ca to move into and throughout your plant (during night and day). I bet once you get night RH under control the plant will be able to absorb and move sufficient amounts of calcium for the plants to thrive without any additional calcium or fertilizer changes on your part.

The long answer:
Rate of transpiration ("E") is the main way Ca and Bo (boron) move into roots; they are essentially sucked in the root with water; unlike other elements that can freely enter root.

Ca movement into and though plants is generally greatest for the first few hours of lights on. That makes sense because at that point E would be at peak levels for the day when RH would be higher and temps would be lower.

For your night RH you need to drop it to at least 60%, better to 50% because night temps are lower, thus night RH should be lower. What is the night time temp at canopy? With your RH as high as it is at night, and night temps less then 75'F (I assume), the "air to leaf Vapor Pressure Deficit" (VPD) will be so low (i.e. < 0.8 kPa) the leaf stoma will start to close down (reduced stomatal conductance). VPD controls, and in some cases, is indirectly controlled by rate of transpiration. Without getting overly technical, high RH (esp. in lower temp) will reduce the plants' E, as will low RH (esp. in high temp). In your night time environment, E will be very much reduced by low VPD. I would easily bet VPD at night is < 0.2 kPa; if so you run a greatly increased chance of fungi attack, which would be more likely to start in the dark than in the light.

Another reason to keep RH below 60%, is if you use carbon scrubbers to remove smell. Activated carbon stops 'working' to remove smell once RH exceeds 65% RH, to be safe keep RH ~60% or lower.

In terms of your day time RH and temp, why is there at 10'F range in the day temp? And is that measured at canopy under shade? I ask because lower RH and higher temps means increased VPD, and that in turn means reduced E. But IMO your day temp and RH are in the fine range.

During daylight hours, E is higher than E at night; but E during both day and night is important in terms of controlling Ca movement into the roots, then from the roots to shoot/leaf (via. xylem). So for day temp, you would be doing well if you could keep the RH at 60% and the canopy temp at 75'F. That would allow your grow come fairly close to ideal VPD (0.8-1.0 kPa), and you should come really close to, or be within, the range of sufficient VDP (1.0-1.25 kPa).

Using VPD (an equation of canopy temp and RH; or leaf temp, canopy temp and RH) is better than RH alone because VPD shows us how plants 'fee' the air-moisture and how they react, in terms of increasing or reducing stomatal conductance, that in turn affects E wither positively or negatively.


Here is a good intro to transpiration, but it lacks into on VPD (interplay between RH, canopy temp and leaf temp):

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Transpiration.html

 

[darrmann]

almost all nutes need cal regimen needs cal mag added. But in cocco it especially needs to be added. cocco soaks up cal mag and a little more then normal needs to be added till the cocco has sucked up all it can and starts releasing it. at that point add as required.

 

[prowler]

Read H3ad's sticky topic in coco forums.

Basics: GH modified lucas formula 6/9 per gallon. pH 5.8-6.0. With tap water you don't need any mg or ca supplement!

One quote from H3ad himself at this topic: https://www.icmag.com/ic/showthread.php?t=188883&highlight=cal

K Ca and Mg are competing ions.
Balancing these elements is important. Excess amounts of any two will cause deficiency of the third. Generally you want more Ca than Mg and more K than Ca. If your pH drops too low K and Mg uptake is reduced.

Follow these instructions and you'll have healthiest plants ever.

 

[spurr]

almost all nutes need cal regimen needs cal mag added. But in cocco it especially needs to be added. cocco soaks up cal mag and a little more then normal needs to be added till the cocco has sucked up all it can and starts releasing it. at that point add as required.

Good commercial mixes do not need calmag+, some could benefit from it, but they don't need it. The Lucas formula has plenty of Ca and Mg, and thepike fertigates with every watering, so the plants are getting plenty of Ca and Mg.

Coco has no more need for Ca than does s.peat, the issue in this thread, I would bet money on, is what I wrote: the rate of transpiration is too low, thus reducing uptake of Ca.

Check out this thread where I explained properties of coco and lots more info about Ca movement into plant, etc. I do not believe the idea that coco needs more Ca, nor that coco needs to be charged. https://www.icmag.com/ic/showthread.php?t=191932

@ ThePike:

how dry does you coco get between watering?

 

[thepike1984]

Temps during the day fluctuate so much because i dont have adiquite ventilation and there for have to have the door of my tent open when i can. Most days i have to open it at certain times and have it closed others due to security reasons.

The plants were becoming yellow with very few rust spots before adding epsom salts. The rust spots appear to have gotten worse since adding the epsom.

I usualy water when i see a few small dry patches on the top of the coco.

Pike

 

[thepike1984]

With tap water you don't need any mg or ca supplement

This would depend on how soft or hard your tap water is.

 

[thepike1984]

Reading over this thread i think im going to go with a) Iv been adding to much epsom salts to my nutrient solution, and b) The rh is way to high when lights off.

Going to flush and make up new nutrient solution with less epsom and a little of the calcium fertiliser i have. Thanks for all the help folks. Big thanks to spurr for all the great info.

 

[spurr]

@ thepike,

I forgot to mention, you should probably spray your plants with 2.5ml calmag+ per gallon of distilled water using a good non-ionic surfactant and a few ml's of humic acid liquid. That will provide immediate Ca to reach the leaf tissue bypassing root > xylem > leaf transport.

The calcium-nitrate (from CalMag+) will easily absorb into the leaf (through cuticle layer and cell membrane) and provide Ca, N (and Mg and Fe from the CalMag+) for the tissue. Adjust the foliar pH to between 6-6.5 before spraying because leafs prefer near neutral pH, and to keep ions highly soluble try to keep pH in the ideal range.

And you should spray soon, before you fix the night time RH issues. The higher the RH the better it swells leaf cuticle layer and aqueous pores, this helps leafs take in ions and organic substances (via. cuticle layer; not stoma). Spray when the HID isn't running, just as night starts, I use a CFL for light to spray. Let the temp clime as high as 70'F and let the RH clime to high as it can. I am not sure how long your night-lengths are, but try to keep the light off for 6-10 hours (ex. cut into hour of light for the next day); the longer the better.

Use of calcium-nitrate is good 3 reasons: (1) it's a good source of Ca; (2) it will continue absorbing into the leaf even when it not in solution (drop of water on leaf) when RH is > 53%; and (3) the ions rather quickly enter the cuticle layer and swell the cuticle layer allowing easier passage of other ions and organic substances (that is why it's good to include calcium-nitrate in all foliar sprays).

The addition of humic acid is to reduce evaporation rate of water droplets from leaf and to benefit the leaf directly.

P.S. IMO don't use DutchMaster Penetrator (now called Saturator), just use a non-ionic surfactant. DM Penetrator and Saturator have the same flaw: they both use ions to swell cuticle layer that have very high POD (Point of Deliquesce) of >~93-95% RH. That means once the leaf looks dry, the RH has to stay above 95% for the ions in DM to continue being absorbed from leaf surface and thus to continue doing their 'job'. The reason is leafs can absorb ions in phyllosphere for many hours after foliar spraying, long past once the leaf looks dry. That is why I use and suggset CalMag+, because the calcium-nitrate acts in the same manner as the ions in DM product (ammonium-phosphate mix and phosphate-potassium mix). But cal-nitrate works better because it has a much lower POD. So you can make your own, better, DM Penetrator/Saturator by using the foliar spray I suggested above.

P.P.S. dish washing soap isn't a good surfactant, it has low % saponin. Therm-X 70 is a good yucca surfactant, I use it at 2.5 ml per gallon, but 1 ml per gallon is also fine. There are some decent surfactants (better than yucca) one can buy at hydro stores; one is called "something-blue", it's a blue liquid, I can't recall the name.

There are really good surfactants used for horticulture and by fire depts. to fight forest fires but they are special order items and come by the gallon to 5 gallon or more.

My base foliar spray I use to apply kelp extract, PRGs, etc.:

(per gallon of distilled water)

• 1-2 ml CalMag+
• 5 ml humic acid liuqid (with 8% HA by weight)
• 2.5 ml Therm-X 70 (or other surfactant)
• pH adjust to 6.00-6.10

 

[thepike1984]

Instead of using calmag+ could i get away with using the products i already have?

 

[spurr]

You can use whatever Ca source you have, I only wrote calmag+ because that I what have used and can vouch for it.