Recurring problem with low ph in coco

[maimunji]

Ok can someone explain me big deal with ph run off and coco. I ask this question many times and ask a lot of people. My grow with coco hempy, hand watering once per day. I watering with a lot of run off to keep plants "happy", beleave me I lost a lot of bottles with nutes to keep my run off same like my rez ph and ppm. Results plants grow with deficiency, yield is crap and quality isn't there.
Next grow is pure coco without run off. One bottle a&b is enough for whole grow. All plants grow very well without deficiency, yeild is heavy and quality is there. When I test run off ph is close to 4.8-5.0.
Just test run off ph from fresh canna coco bag watering with tap water 8.0 ph comes out 5.2.

 

[noyd666]

* By the absorption of nitrogen and phosphates in the first two to three weeks, we often see the pH of the medium rising, Light-green small leaves at the top of the plant are one of the characteristics. It is very important to use B.A.C. Root Stimulator and Foliar-Spray during this period. Our root stimulator contains a pH reducer. Around the 6th week of the bloom period the growth medium usually has a low pH, as we are adding a lot of PK elements to the plant from that time. Potassium results in a lower pH value around the roots. Therefore it is essential to add B.A.C. Bloom stimulator in the bloom phase, as this stimulator has a pH raising effect in the root environment. When the pH is a little too high/low, you need to adjust the pH from the nutrient tank. With soil and coco you will depend on the chalk buffer. When the medium runs out of lime/chalk, the pH will definitely fall and you are beyond help. So always upgrade recycled soil or coco with chalk. this might help its out of BAC-NUTRIENTS TIPS. GOOGLE.

 

[spaceboy]

Well I have taken a little advice from everyone on this one and also went with my gut which was to hit them with nutes plus my super alkaline tap water which comes out of the tap at 550 ppm which my nutes brought up to 950 ppm or about 1.4 ec with a ph or 6.3. Flushed the pots with this until I my runoff was coming out at 6.2.

The plants greened up within a day and are looking beautiful now, but i have been keeping a very close eye on runoff and looks like its creeping back down as the runoff was as low as 5.6 on a few plants.

They have all been getting the tap water plus nutes at 1.4 ec ph of 6.3 for last few days and being that my water is about as alkaline as your ever gonna find I'm really surprised it was able to pull it back down there that far.

Luckily almost all plants look much healthier, but im still worried there is some other problem bringing my ph down. This is what has been happening the last few rounds, which is id flush flush flush and get runoff back up and then within a few days it crashes back down.

I'm really hoping that the few plants with low ph did not get flushed enough to begin with, but also starting to wonder if there there is some sort of bacteria or pathogen at play here. Root health is very good, but I suppose there could still be something I can't detect.

 

[spaceboy]

This was yesterday. Looking almost completely restored today.

 

[Chimera]

Nice to see that green coming back.

I suspect your plants are using more water than food, meaning the nutrients are being left in the medium, again causing the pH to crash as per the previously posted document.

You could likely get away with feeding at an EC of 1.0 or less, meaning there would be less nutrient left in the medium, which again as stated is probably the reason your medium pH has crashed. Your higher nutrient levels have exhausted the buffering capacity of the coco, so any changes pushing pH down have an immediate effect/impact.

The most successful coco gardens I have seen implement a weekly flush to minimize salt buildup. Another way to achieve the same result and cause less environmental damage (and save you money on nutrient), is to simply reduce the nutrient concentration, for eg feeding at EC of 1.0 or 0.8 rather than up near 1.4. These are some ideas you may wish to experiment with to see if this problem goes away.

I'm glad to see you back on track, good luck with the rest of the cycle.

-Chimera

 

[spaceboy]

Thanks Chimera, I think your probably right, but the runoff hasn't been very high in ppms, about 200 to 300 more than I'm putting into it. Do u think that is enough to do it? The room is sealed with Temps in mid 70s, but my co2 generator has been down for the last few grows and haven't been able to replace it yet. Any chance that lack of co2 could be causing the plant to not process all of the nutes?

 

[spaceboy]

Well unfortunately still having the same exact thing happening. . Most plants are very happy, but on some the ph keeps crashing back down to 5.5-5.6. I've lowered my nutes to 1.0ec which 300ppms of that is my tap water, so about 400 ppms of base.
Also running my ph at 6.3-6.4.

My next step is to sterilize the medium with some bleach, but my roots look nice and white. I added some gypsum to the top of a few, really hoping that helps, but back I'm at a loss. My tap water comes out at 550ppm, but I'm using ro.

Also wondering if because my water is so alkaline before it goes through the ro that it just crashes very easily. I'm really running out of ideas though. I am going to contact dyna drop too and see if they have had any similar reports.

 

[maimunji]

If you want read thread the salten coconut from c64 there I asked him many questions about water and ph stability. He explain me very well with a lot of knowledge.
Roots looks good.
Do you have other brand nutes to try? Just on some of the sick plant?

 

[spaceboy]

Thanks I will check it out. Definitely the kind of information I'm looking for right now. I don't have any other nutes at the moment, but I'm about to switch to something, just not sure what. I have really liked this dynagro up until now.

 

[Suntana]

This is an old thread but good info. He has a few spelling errors to figure out lol

The Chemistry behind Coco Coir: a (strange) journey from ferts bottle to to buds

/ icon and title message
Growing is something strange as it can be as much complicated as you want. Beside that, some growing methods needs a better understanding of the involved chemical processes than others. Coco coir (in my opinion) is one of them.

"Coco Coir tend to adsorb Calcium and Magnesium", "pH of nutrient solution should always be adjusted to the correct value", "checking drainage ec and pH is also important" as well as "checking drainage pH and ec makes no sense as coco holds nutrients and modify pH", "Coco is an inhert media"or "Coco has high CEC" are only few exemples of how many confusing infos can be found on the internet.

If you haven't heard none of this rules before, you are likely to have never grown in coco or at least, you were lucky enough to not need search the web for hints and tips.

Some of those rules are true, others are not, but in most cases they're only simplicistic aproximations of reality.

So, are you ready?

Step 1, the basics: pH, salts and Ions (aka the good, the Bad, the Ugly)
"Daddy, why seawater tastes that baaad?"
"Ohhh it's easy my son, it's cuz there is salt in it!"
"Wow you know lot of things daddy, but what is salt?"
Bump! Panic "ehm, son, why dont you go play with your friends now? It's summer! Have fun!"

Encyclopedia, Salt: elettrically neutral chemical compound, made of 2 or more Ions with opposite electrical charge.

Lets take a look at the seasalt, almost everybody knows that its chemical formula is NaCl. In its solid form is a quiet stable compound, but what happens when we put it in water?
Correct, it dissolves, but what it means?
What actually happens is that salt divides in its Ions: Na+Cl-
If we want to be exact, there is no salt in the solution, its crystalline structure got dissolved, just positive and negative Ions. Keep those last word in mind and put them in a corner, we'll need them soon.
Everything clear till now?
Good, lets go ahed.

Water!
Water has many characteristics, almost everyone quite unique. But when the talk is about Ions, two becomes particullary important: water is an amphoteric and polar compound. Lets start from the last one.

While the term "polar" could suggest something related to cold places, it actually referres to magnetic/electric poles. Saing water is "polar" simply means that its molecule is electrically asimmetric. Everybody knows water chemical formula is H2O and if you don't, please, pick up a lighter and set your hair on fire for punishment.
So 2 Hydrogen atoms and 1 Oxygen, but maybe not everyone knows that its structure it's like that:



As you can see, water molecule has some sort of triangular shape, with the oxygen side been slightly (it all depends on the point of view) negative charged, and viceversa.
Could seem a little thing, but without this there would be no plants to grow.

Amphoteric is somehow a weird word. Anyway it basically means that water can act as an acid as well as a base. For definition, an Acid is something capable of releasing H+ ions, while a base is something that attract them. If put thogeter with someting more acidic, water will act as a base and viceversa

Pure water at room temperature is made of stable H2O molecules, but a really small amount "divide" to H+ and OH-

Beware that "divide" is not correct, is more of an addition:

2 H2O <--> H3O+ OH-

At the end of the day it's basically the same thing, we always have a H+ on a side, and a OH- on the other. From know on, please consider H+ and H3O+ as the same thing. In most reactions you'll see H3O+ cause it's the real form, while when talking we'll refer to H+ for easier reading.

Anyway, I sad "only a small amount". Guess how many? 1 every 10.000.000 or 1 × 10-7. Look at that "-7". Ever wondered "why pH7"? now you know.

As we have seen pH7 also mean that H+ and OH- are present in the same concentration.
If you use RO water, thats quite near what comes out from the blue hose

But if we put an acid in it, water will act as a base, bonding to an H+

H2O + HCl -> H3O+ Cl-

More H3O+ compared to OH- The pH is lowering. Ten times more H+ means 1 point less in pH.

Viceversa H2O+NH3-> OH- NH4+
More OH- compared to H+. The pH is rising.

So I've just said pure water has pH7 so same amount of H+ and OH-.
Oh, well, there's a last minute problem, like when you see there's only 10gr left and you're still in Veg: pure water is a great solvent, enough powerful to react with CO2 normally present in air to create Carbonic Acid.

H2O+CO2 -> H2CO3

Being H2CO3 an acid, water play its role as a base, actracting H+ from the newcomer and lowering pH till a 5.5 value.

Why till 5.5 and not more? I've said water act as base when toghether with someting MORE acidic. In that case, 5.5 is the equilibrium point. Maybe you are allready thinking that adding your pH+ would be a simple solution but think about it: if you raise the pH, water will be once again basic if compared to H2CO3, at that time will start to act as a base as before.

Seems frustating doesn't it? Well, actually it's a great thing: the fact is that water by its own has a very low inertia to pH adjustment. In other word, easily matches pH of surrounding substances.

Know you should start to understand why the amphoteric behavior is so important.

But what about polarity?

The answer is quite simple (or at least more simple than the amphteric thing): polarity enables water dissolve salts crystalline structure and idrate positive and negative Ions.

Look at the picture below:
Salts in a water solution are like you and your girl dancing in the middle of 1000's Bred Pit & Angelina Jolie straight in the middle of a 7th year crisys.

Few minutes later, the situation will likely be like that on the right



Now stop thinking angelina's green eyes for a while (yes I am a romanthic guy) and focus on female plants. Fertilizers are salts, but plants need them in their ionic form to be able to adsorb them.

Now you know what salts and Ions are, how water acts like, and what happens when those 3 are put togheter.

"Wait, but the title said pH, salts and Ions, not water, salts and ions!! What da f**k was that for??"

Well, pH is like balance between brads and angelinas. Too many Brad and only few Angelina will make them forget about the 7year crisys and try hard to reconquest the few remaining ledies. In three words: you are screwd.

If you kept reading till now, i'm quite sure you have seen this graphic before:



I'll not explain them one by one, but keep in mind that any significative change from pH7 could cause serius issues. As said before, 1 point more in pH means 10 times more OH- and 2 point more means 100 times more OH-, the opposite for H+ ions.

Roots use H+ and OH- to adsorb macro and micro elements, so pH balance in the nutrient solution is very important to make it possible. Beside that, different pH causes different equilibrium between ions, making possible reactions that doesn't happen under neutral conditions, resulting for example in unsolvable salts.
Undissolved salt means (quite) no ions, and no ions means no food for the plant.


So now you should have a clearer view of what happens when you mix those high quality ferts in water.
But in wich way plants actually eat (or maybe drink) them?
On a chemical level, two main things come in place: osmotic pressure and ion exchange.

Before we start there is a very important thing you must have clear in mind: everything in chemistry goes in the direction of maximum equilibrium or, if you prefer, maximum stability level.
Salts dissolve into Ions simply because, when put side by side to water molecule, that is the most stable form. If something changes (pH for example), also equilibrium point will, and things will start moving again seeking the new stability level.

Osmotic pressure and ion exchange makes no exception: they'r all about stability and equilibrium.

Osmotic membranes (like cellular membranes) are also called "semipermeable membrane". Basically, it means that they are able to let some molecules (like water molecules) pass trough, while blocking others (like ions).
At the same time, osmotic pressure is an intrinsecal chemical property of solutions. The lower the concentration of ions, the higher the osmotic pressure.
If concentrations, and for direct conseguence osmotic pressure, on the two sides of a semipermeable membrane (like root cells membrane) are different, water will be forced to move from the higher pressure side (low concentration) to the other (high concentration). Once the concentrations on the to sides are the same, so will be osmotic pressures: equilibrium has been reached. Under normal conditions, ion concentration inside root is higher than that in the nutrient solution, so water will be literally pushed inside roots trought their semipermeable membrane by means of osmotic pressure.

So, while water is somehow "pushed" inside plants, ions are litterallh captured by them.
We just said that water inside roots is quite rich in ions, and this is a key point. Some of those Ions are micro and macro elements that were already adsorbed, while others are simply H+ and OH- resulting from water dissociation.
Since like every Ion, micro and macro element ions in solution have their own electrical charge (K+ for example) plants can't just "take" them, otherwise equilibrium would be broken. What they actually do is swap them with equivalent amount of H+ and OH-

For exemple

potassium (K+) swapped with 1xH+
calcium (Ca++) swapped with 2xH+
magnesium (Mg++) swapped with 2xH+
ammonium (NH4+) swapped with 1xH+
iron (Fe++) swapped with 2xH+
manganese (Mn++) swapped with 2xH+
zinc (Zn++) swapped with 2xH+
nitrates (NO3-) swapped with 1xOH-
phosphates (HPO4--) swapped with 2xOH-

In this way electrical charge equilibrium remains the sama and at the same time, roots releasing H+ or OH- make pH fluctuate.
This is a well known behavior for hydroponic growers, where there is quite no buffering power in the media to oppose to this.
I said buffering? Keep reading...

Step 3, those damn colloids! pH buffering and Cations exchange capacity in coco coir

Coco coir is characterized by a quite high colloid content and therefore, good CEC or cation excange capacity.
Keep in mind that "Cation" is just another name for positive charged ions, so this basically quantifies the substrate ability to exchange positive charged ions (with nutrient solution as well as with roots)

Now, imagine colloids as big spheres with a negative charged surface. Being so big and at the same time having such a strong electrical charge, makes them able to bond to a very large amount of Cations (+Ions).
Even if electrical charge has the same "weight" between different ions (for example K+ and H+ or Ca++ and Mg++) Ions are still differently attracted by colloids. Many factors come in place like ions dimensions and steric configuration for example. Anyway, the most important one is still the electrical charge, so Ca++ and Mg++ are more easly abtracted than, for example, H+ or K+.
This is very important, and explains quite well why its common tought that extra Ca/Mg are needed when growin in coco.
I said common tought because, in fact, the plant need the same amount of Ca/Mg in coco as in other substrate. Its just a matter of fullfilling CEC.

So, we have seen that coco can retain some Ca/Mg beside other Cations as well, but is this GOOD or BAD?

The answer is neither one or another. In fact, coco acts as a buffer on nutes level. Once the CEC is fullfilled (for example by multiple feeding or, better, one night submerged in the nutrient solution), colloids will have reached an equilibrium with nutrient solution. In this situation, if we feed pure ro water, colloids will release cations, if we feed a very high ec solution, colloids will be forced to bond to more cations.

This is also true for pH buffering. As H+ is a Cation, colloids will abtract them in great quantity. If we feed high pH solution (lot of OH- and few H+), colloids will release H+ and viceversa. As we have seen before, its all about equilibrium.

So, its now clear that the most important part is correctly fullfilling its CEC. This can be easly achieved by letting coco coir sit in a balanced nutrient solution with correct pH level for some time (say, for example, a night).

This also mean that checking in/out ec is important too. Inlet ec higher than out ec means colloid are actracting ions, while inlet ec lower than out ec means colloids are releasing ions. This is a very usefull information about CEC in that specific moment and also suggests if corrections are needed.

Regarding pH, providing a nutrient solution corrected to the right value is not bad, anyway slight deviations from correct pH value will be at most compensated by the coco coir it self.

At the same time, tring to keep run-off pH at the correct value by changing pH input could do more harm than good. As we have seen before, pH fluctuation is a natural conseguence of ions exchange operated by plant roots. Beside that, having a substrate that also affect pH makes thing even more complicated.

At the end of the day, you should correct pH if your starting water has high ec (that means high Ca/Mg wich act as pH buffers). An high buffered water will make it more difficult for the colloids to bring pH to the correct value (as an high buffered water will need higher amuont of H+ ions to change it's pH if compare do low buffered / low ec waters).
Long cicles with such water at very high pH could, week by week, unable the substrate capacity of compensating pH (anyway this is a very rare situation)

Using ro water or tap water with medium or low ec (say <0,4) usually makes pH correction quite useless.
As we have seen, water without buffering ions vary its pH very easly so an incorrect value should be quickly compensated by the substrate.

Step 4: think think think

So, if you came here honestly, and you really red all that boring stuff up there, you shuold have already made your mind about what to do and what to avoid when growing in coco.

Any way, lets review the key points:

- starting water: the best solution is to use tap water if ec is <0,4 or slightly higher. With high EC tap wather, is really suggested to use a RO system, than cut RO water with tap water till 0,3-0,4mS/cm

- pH: if your starting water is like the one mentioned above, pH adjustment shouldn't be necessary. You can always adjust nutes pH but please, do not rise or lower it to achieve correct run off pH: it doesn't make any sense. Run off pH can fluctuate a lot due to roots activity, and that's absolutely normal

EC: of course you should adjust your feed EC to the right value. It's also very important to check for run off EC once a week more or less. Run off EC should be as close as possible to feed EC. If you find it lower or higher a good way to take it back to normal is to just increase your feeding time. For example, if you are feeding 2 times per 10 minutes each, switch to 2 times 12 minutes.

Feeding Times: you should adjust your feeding time to achieve a sufficient run off. That way you can assure coco CEC is always buffered while also preventing salts build up. You should also adjust number of feeding to let the substrate dry a bit between a feed and the other.

Pot size: best results are achieved with a pot size that enables you to give up to 3 or 4 feed per day when the plants are in the maximum need. It usually means quite small pots.

Perlite and clay pebbles: by washing your coco coir before seedling (remember the "fullfilling cec" thing?) you should also wash away all the finest dust so you end up having quite large fibers. In that situation, you really doesn't need perlite. If you're missing it, you should consider to use smaller pots rather than adding perlite.

Hope it helps!

TC

 

[Stay Gel^N 247]

This was yesterday. Looking almost completely restored today.

Looks good. You can add I little silicon to naturally help with pH drift. It's good for the stalks and the leaves also.

 

[issack]

This is great info. Because I have been feeding with 6.5 to 6.8 ph R/0 and have been seeing amazing results with my ppm at 650. If I go down to 5.3 I see slight overferting and some deficiencies and then that adds up over time.

 

[Mikell]

Thanks Chimera, I think your probably right, but the runoff hasn't been very high in ppms, about 200 to 300 more than I'm putting into it. Do u think that is enough to do it? The room is sealed with Temps in mid 70s, but my co2 generator has been down for the last few grows and haven't been able to replace it yet. Any chance that lack of co2 could be causing the plant to not process all of the nutes?

You're running a sealed room without CO2?

Do you check the monitor to observe CO2 levels during light cycle?

300ppm is a lot. I like to see within 10-15% of what is going in.

 

[Suntana]

This is great info. Because I have been feeding with 6.5 to 6.8 ph R/0 and have been seeing amazing results with my ppm at 650. If I go down to 5.3 I see slight overferting and some deficiencies and then that adds up over time.

I have been keeping it around 650 ppm, but I ph to 5.8 and my run off ph is around 6.2 - 6.4 my plants have no deficiencies and look great. I'm baffled how guys get away with 1200 ppm every feed.

 

[madc]

Any update on this issue?

Any update on this issue?

How are you going with this? I have had similar problems with coco Ph crashing.
My water is soft <20 ppm and i feed lightly @ 350 ppm once a day. They look great for the first month or 2 then ph drops to around 5 or lower and issues start just in time for flowering.
No amount of flushing or feeding at higher ph makes any difference.
It seems like once the buffer is broken it cannot be restored.
I use lucas formula with maxibloom and calmag in waytogrow bufferred coco.
Would be great to get an update from the OP on whether you solved this issue or not.

 

[zeke99]

How are you going with this? I have had similar problems with coco Ph crashing.
My water is soft <20 ppm and i feed lightly @ 350 ppm once a day. They look great for the first month or 2 then ph drops to around 5 or lower and issues start just in time for flowering.
No amount of flushing or feeding at higher ph makes any difference.
It seems like once the buffer is broken it cannot be restored.
I use lucas formula with maxibloom and calmag in waytogrow bufferred coco.
Would be great to get an update from the OP on whether you solved this issue or not.

Could it be that you're not feeding with a strong enough solution? Dependent on your level of lighting, 350ppm in late veg into flowering could be on the low side.

 

[mushroombrew]

I would take a look at your nutrients.

The balance between Ammonium Nitrogen(NH4+)
and Nitrate nitrogen (NO3-) may be "off"

When plants feed on NH4+ they release H+ and pH goes down.

When they feed on NO3- they release OH- and pH goes up.

Maybe you have too much Ammonium Nitrogen in your nutrients. The ratio should be stated on your "grow" bottle.

I would use Nitrate Nitrogen only in your situation and see if the pH stabilizes.

 

[mushroombrew]

If your run off is that much higher back down your TDS. And for sure no CO2 means lower nutrient requirements. My plants eat almost 20% more with just 800ppm CO2.

 

[madc]

g

Could it be that you're not feeding with a strong enough solution? Dependent on your level of lighting, 350ppm in late veg into flowering could be on the low side.

Thanks for the response. It is possible but only running em under a 250 watt hps. I was thinking the same thing so tried upping the feed and started getting yellow tips
Going by runoff and how they looked before ph crashed it seems to be at the right level.

Is it your experience that coco is this hard to flush? Running 10-20 times the volume of ph 6.5 water through the pot and still cant get runoff the same as what i am putting in. Got it up to around 5.9 in runoff but as its going in higher that would mean the medium is still a bit lower than 5.9. Now as soon as i feed it @ 300ppm ph 6 the runoff ph was back down at 5.3. Something is pulling it back down.

can you get a bad batch of coco maybe?

 

[madc]

I would take a look at your nutrients.

The balance between Ammonium Nitrogen(NH4+)
and Nitrate nitrogen (NO3-) may be "off"

When plants feed on NH4+ they release H+ and pH goes down.

When they feed on NO3- they release OH- and pH goes up.

Maybe you have too much Ammonium Nitrogen in your nutrients. The ratio should be stated on your "grow" bottle.

I would use Nitrate Nitrogen only in your situation and see if the pH stabilizes.

Thanks for your response. I am running maxibloom so i would imagine this issue would have come up before if it was a problem considering that it is used in the KISS approach.

maxibloom total Nitrogen = 5% ammoniacal Nitrogen 0.5% Nitrate nitrogen 4.5%. I dont have seperate nitrogen source to try this atm.