Is this potassium deficiency?

[Dalaillama]

It looks little bit like it but I'm not quite sure. These have been growing in DWC for several weeks. Start was slow because of too weak nutrients. Now they have been really good for few weeks until now they started to show some browning at the edges of the older leaves. I haven't adjusted solution after they started to do well and I really doubt that it would be any deficiency because I have been using full strength lucas formula.

EC has been around 1600-1800uS. Still it really looks like it is some deficiency of the mobile nutrients as it has been started from the bottom leaves. If it would be nutrient burn should it kick in earlier and also effect younger nodes? They really seemed to like this Lucas ratio (8/16ml per gallon micro/bloom) for few weeks and now they have been showing these symptoms for few days. PH has been around 5.5 to 6.0.

Lights I haven't been adjusting and heat stress would probably harm more newer shoots reaching closer to the bulb. One factor that I cannot be sure is RH. It might have been little bit low. Might that cause this type of yellowing of the lower leaves?

 

[Dalaillama]

Attachments got lost in transmission.. Here they are.

 

[Sat X RB]

no, Mate, not K def ... it's not so simple as that.

the inter-veinal yellowing looks like Mg def ... but the tip/edge scorching is nute burn.

so with that combination of symptoms something fundamental is wrong with yr process.

I 'm not a hydro man just a plant lover so I can't give specific advice. except start by giving yr plants a BIG flush with plain water and check the basics of yr process. whatever is wrong has to do in some way with pH ... and perhaps overfeeding.

good luck ...

 

[RetroGrow]

What's the medium? Have you checked leaves for broad mites? You will need a 100X scope and should check under the leaves for eggs. Google "Broad mite eggs" for pictures of what they look like. These often look like potassium deficiencies. Also check your root zone for root aphids. Those do look like root aphid symptoms.

 

[Dalaillama]

I'm growing in DWC. Baskets filled with hydroton, no rockwool inside. I have to look more in to that pest subject. What is the best way to fight these broad mites and root aphid?

If this is magnesium related other nutrients can lock it up. I have heard that tap water calcium might give troubles. Tap water here is containing 20mg/l (20ppm) calcium, 1,5mg/l Mg, 6mg/l Na and EC 159uS. This sound quite decent to me. Excessive P and K might also lead to mg lockout. Using Lucas Formula, I haven't read about that kind of troubles. Maybe I still flush the system and try little bit weaker solutions at first even though they seemed to thrive in present solution for two weeks or so..

 

[Granger2]

Not humidity, but Hygrometers are cheap. Get a cheap one at big box. Start with a good flush like SatX suggested to fix lock out if that's it. I think your tap is fine. Keep a close watch on pH. Are you giving them Mg, or CalMag? Do Retro's pest inspection, though I don't think its Root Aphids, but it's possible. Good luck. -granger

 

[symbiote420]

Looks like a K deficiency to me too or either the lamp is too close. Plants need more K in low humidity situations .....this is a guideline I use to help diagnosing problems

N = growth
p = roots/fruits
K = health
If I get a growth related problem I look at my N level 1st and vise versa. Could be pest too, but I doubt it! I use a little extra seaweed or Roots Organic Extreme Serene to avoid or correct it quickly .....keep in mind the messed up leaves an't be repaired though!

 

[Dalaillama]

More K in dry environment sounds interesting. Outside temps have been quite low and I run out of humidifier tray before this problem occurred. I have never heard about this K vs. RH relation.

Have to keep that in mind. I have two ways of keeping RH up: 5 gallon bucket with towel suspended on the rim and second is wide tray under the fan. This wide tray ran out of water but it didn't give any instant indications of problems so I thought that is ok.

I have never seen any photos of plants suffering from low RH. How is that usually looking? I guess plants evaporate more in dry and if EC of the solution is high they cannot drink as much as they want and they will eventually look like they are under watered. but that's just a guess..

 

[Dalaillama]

Last post was written in a hurry and seems little bit unclear and incomplete..

By low outside temps I meant that heated spaces tends to get very dry when this cold outside air is heated to proper indoor temps. Lamp should not be too close it is 400w about 10 inches away and fan is constantly blowing hot air up as this is vertical setup. If it was heat stress should it be affecting upper leaves most as they are closer to bulb? I guess that is not the problem.

I now flushed the system and even changed product line from Advanced Hydroponics of Holland to GHE. AHH should work with Lucas but just to be sure I changed nutes to GHE.

 

[Sat X RB]

If this is magnesium related other nutrients can lock it up. I have heard that tap water calcium might give troubles. .

you are quite right about excess Ca locking out Mg. this occurs with other mineral interactions too (google 'Mulders Chart' to see more).

however it is most likely that the Ca in yr tap water is in such a chemical combination that it is not soluble and so will NOT interact negatively with yr nutes. so excess Ca can be removed from the list of possible troubles.

it's more likely the pH of this water will have a negative effect.

cheers!

 

[ozzieAI]

what do your roots look like?

looks like RA to me as well, but they can mimic a whole range of plant def...

good luck...

 

[Finklsteinshtkd]

Mg and Fe def. What is your PH? When was the last time you changed your rez? I would change my rez to fresh full strength nutes if you're using true lucas formula. By Lucas, are you using the three-part (GMB) version of the GH series (true lucas 8m/16b), flora nova, or floraduo?

Are you using anything else or any additives with your lucas and water? Are you keeping your PH between 5.2 and 6.5/6.8-ish?

Seems like either:

1: PH and thus creating Mg and Fe deficiency assuming you're using full-strength Lucas.

2: You're not actually using full strength Lucas because you're afraid of pulling the trigger.

or

3: RA or something of the sort..

Again, just my two cent, but go back to the basics and do a rez change. Figure out where you're going wrong. It's not rocket science, you'll figure it out..

 

[Dalaillama]

I don't have pictures of the roots at the moment but I checked them quite closely and did not find any Root Aphids or any other pest related.

I have been using this three part (GMB) nutes made by Advanced Hydroponics of Holland. Macros are almost identical with GHE flora series. However I switched to GHE, flushed all systems and put GHE Micro and Bloom according to Lucas formula. Lets see if that was the problem.

First AHH seemed to work pretty well. I mixed 8ml M and 16ml B to gallon. That gave about 1800uS of EC. Plants thrived for few weeks in that solution after they started to give symptoms seen in the pictures. I didn't dare to give more nutrients as the EC maintained pretty much on the 1700-1800uS range. Like in the pictures tips are curled and burnt so nute burn cannot be ruled out.

Situation is quite problematic. By looking the EC there should be enough nutes to not to give any deficiencies still it looks like there is one. Let's hope it is corrected by switching to GHE from AHH.