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Drastic pH drop overnight with Mega Crop in DWC
- Thread starter regal8r
- Start date
JimMuscles
Active member
Co2 saturation causes ph to drop. While your plants may be getting enough O2, you may be adding too much aeration thus too much co2 . I noticed this when i tried to bubble chlorine out of my tap water, that the ph dropped. It happens to everyone , just not as fast. Also you have the carbonate , or kh levels , which corelate with ph as well. And megacrop has organic components and humic acid which both, according to this article on fishkeeping, https://www.practicalfishkeeping.co.uk/features/articles/co2-striking-the-balance lower ph. Im not so familiar with the kh thing, but its in that article .
Megacrop is a good all around nute, but i dont think it excels as much at hydro . Its great for its simplicity , but idk if its as buffered as pure salts, and the uptake is slower/different. I use it now, in coco because it easy, and harder to burn my plants.
Megacrop is a good all around nute, but i dont think it excels as much at hydro . Its great for its simplicity , but idk if its as buffered as pure salts, and the uptake is slower/different. I use it now, in coco because it easy, and harder to burn my plants.
regal8r, it sounds like you have too much air for your reservoir size. The 5g bucket should be just fine, the goal is to have the swing take place over 7-10 days at the start of flower.
Can you do an experiment?
- Check the pH of the res
- Turn off the light and turn off the airpump for 15 minutes
- Check the pH again
Is the pH higher or lower? If the pH has dropped, you have too much air going through your 4'ish gallons of solution.
I do know a few growers who start with a mild strength solution, pH'd to 6.0'ish. They do not top off daily, and the evaporation due to aeration over time causes the solution to concentrate over time. The pH is at around 5.4-3 when they eventually re-fill with whatever nute solution they top off with. I thought it was a lot of stress on the roots, being dried out for so long between re-fills. I knew both growers only briefly.
Englishrick, good point! I've never even thought of that being a 'feature' of nutrients.
In either case, reversing the process is indeed the solution as Hydro8 explained. At some point in the swing, they both allow cannabis free absorption of each element. .
I will try this experiment later tonight and report back.
I did try Hydro8's solution and it seems that it could be a decent work around if the MC isn't optimal for DWC re: pH buffers. I pH'd to 6.3 and 24 hrs later it was down to 4.8 vs <4.0 when starting at 5.4 pH. Plant looks pretty happy. https://i.imgur.com/yjeto4w.jpg
JimMuscles
Active member
MCs not "optimal" for the fastest growth, but it still works great and think of the money and time youll save!
A funny thing , i bought a pack of tums, and looked at the label just now. The active ingredient is calcium carbonate ! That is kh! Maybe you can use tums as a buffer to keep the ph more stable? It works on stomach acid lol but im not sure about plants lol i just thought it was funny.
A funny thing , i bought a pack of tums, and looked at the label just now. The active ingredient is calcium carbonate ! That is kh! Maybe you can use tums as a buffer to keep the ph more stable? It works on stomach acid lol but im not sure about plants lol i just thought it was funny.
I have tested my Apera pen to the GH pH drops and they are both pretty close. Hard to tell with the drops obviously. I took your advice re: pH'ing higher and it's still dropping a lot but I'm just gonna roll with it for this grow bc like you said, plant looks normal and healthy and should remain that way as long as I keep monitoring and adjusting my pH.
I realize now that there is just too little solution volume to effectively buffer pH changes with a plant of this size and how much it's drinking. We're drinking a gallon per day now with my 2x2 SCROG completely filled AND dense foliage under the canopy but above the SCROG. I will probably end up getting a water pump and aux reservoirs and switching to RDWC since I will also have to leave town for about 5 days in a few months and I have no one to take care of the plants.
With RDWC, if I go with let's say 20 total gallons for 1 plant in a 2x2 SCROG, how long could I go without having to do a water change? Right now I'm changing solution every Friday, but with increased res volume I think I could get away with at least twice a month. Does that sound right? Thanks for your help.
Hydro8
Member
A reservoir makes things so much easier to manage and keep consistent.
One thing that will be important to maintain for 5 days is the volume level. When plant is small, 5 days with a 20 gal res the level change would be minimal, when a plant is big it can drain a gallon or so a day.
However much the level drops in your res is how much it will drop from net pot. You could test it by getting a tote/reservoir and taking 5 gallons out and see how far the level drops.
I had a 15 gal reservoir on two 5-gal buckets/plants I would leave it for 2-4 days in flower no issues the level would be down 3 inches or so, the plants seems unfazed. More then 3 inches down would make me feel uncomfortable.
One of my next experiments is an auto feed for a reservoir, a raised container with a tube that will gravity feed into the reservoir when the level gets below it. If it works it would keep the level constant and I could leave for a week or so.
I like to change my nutes at least every 10-14 days closer to 7 in flower. Some guys will run the same nuts for 30 days or more. 7-10 days just seems like it keeps everything clean, fresher and the plants seem happy.
Douglas.Curtis
Autistic Diplomat in Training
Sorry, I did not realize the size plant you have in your 5 gallon bucket. You seriously do need a larger reservoir to slow your pH changes. A 15 gallon res, with about 10-12 gallons of water would be about right. Your goal should be around 7-10 days for a full pH swing at the beginning of flower. This shortens as demands increase in flower, and will stay within safe ranges.
Personally, I don't recommend RDWC. At the end of flower, my DWC reservoirs are still clean. I use zero chlorine, h202, enzymes or other products to keep it clean. The DWC setup is a simple tub, with airlines and airstones. All of the additional cracks and crevices from plumbing in RDWC makes this nearly impossible. In addition, RDWC costs more to build and run than DWC and the outputs are the same.
I have a couple 18 gal totes sitting around that I think I'm going to use instead of going RDWC. They fit my grow area perfectly so it's gonna work out pretty nice. Thanks for all the advice.
Agreed on all accounts. I have a couple 18gal totes I'm gonna move to. Thanks!
Agreed on all accounts. I have a couple 18gal totes I'm going to move to. Thanks!
Douglas.Curtis
Autistic Diplomat in Training
That will help significantly. Should you end up with too slow of a pH swing, lower your solution level a little and it will speed up.
This is from the canna website
During the growing phase, plants tend to cause the nutrient solution’s pH to rise. This happens because at this stage the roots can excrete relative large quantities of elements that increase the pH. During the flowering phase, the reverse happens: the roots now produce acidic secretions causing the nutrient solution’s pH to fall.
To a large extent, the nutrient solution’s composition determines whether or not the roots excrete predominantly alkaline or acidic secretions. By using different nutrient solutions that are customized to the different phases of the crop (vegetative and generative), you ensure that the pH remains as stable as possible.
Trace elements
Trace elements present in the water also have an effect on the pH during cultivation. In hard water areas (high bicarbonate content) the nutrient solution’s pH shows a tendency to rise after the solution has been prepared and the pH balanced. By balancing the nutrient solution with a lower pH value (5.2-5.3), more bicarbonate is neutralized and the pH shows less tendency towards rising. In soft water areas with low bicarbonate content (osmotic water) drops in the pH value are more likely to occur. This is because soft water has less pH buffering capacity than hard water and this is also the reason why in soft and osmotic water regions nutrient solutions must be prepared with a higher pH (5.8-6.2).
If the pH is too low, certain nutritional elements such as iron and manganese, as well as the toxic aluminium, are dissolved more easily, which can cause damage as a result of over nutrient availability. If the pH drops too low it is sensible to raise it by using a caustic product containing bicarbonate. In doing this, you not only increase the pH, but also the nutrient solution’s pH buffer.
pH fluctuation with Aqua
infopaper-aqua_text_12.png
Influencing pH
Plants are capable of actively influencing the nutrient solution’s pH. If the intake of food is disturbed when the plants suffer a pathogenic attack, for example mould, it can cause the nutrient solution’s pH to drop below 3. Another symptom can be noticed with iron deficiencies and, in this case, the pH is actively lowered to make iron more available to the plants. For this reason, it is not advisable to have the same value for the pH continuously. With a good nutrient solution and a pH between 5.2 and 6.2 there should be no nutrient problems. If the pH should be lower than 5.0 or higher than 6.4 for a few days, it is advisable to carry out manual adjustments or to change the composition of the nutrient.
If Vega is being used and the pH drops too low during the twelve-hour cycle, changing to Flores nutrient is recommended (Flores is less acid; it is important to note that the plant now receives nutrient that is the best possible for its bloom). If the pH is too low, it increase with CANNA pH+ (Pro).
During the growing phase, plants tend to cause the nutrient solution’s pH to rise. This happens because at this stage the roots can excrete relative large quantities of elements that increase the pH. During the flowering phase, the reverse happens: the roots now produce acidic secretions causing the nutrient solution’s pH to fall.
To a large extent, the nutrient solution’s composition determines whether or not the roots excrete predominantly alkaline or acidic secretions. By using different nutrient solutions that are customized to the different phases of the crop (vegetative and generative), you ensure that the pH remains as stable as possible.
Trace elements
Trace elements present in the water also have an effect on the pH during cultivation. In hard water areas (high bicarbonate content) the nutrient solution’s pH shows a tendency to rise after the solution has been prepared and the pH balanced. By balancing the nutrient solution with a lower pH value (5.2-5.3), more bicarbonate is neutralized and the pH shows less tendency towards rising. In soft water areas with low bicarbonate content (osmotic water) drops in the pH value are more likely to occur. This is because soft water has less pH buffering capacity than hard water and this is also the reason why in soft and osmotic water regions nutrient solutions must be prepared with a higher pH (5.8-6.2).
If the pH is too low, certain nutritional elements such as iron and manganese, as well as the toxic aluminium, are dissolved more easily, which can cause damage as a result of over nutrient availability. If the pH drops too low it is sensible to raise it by using a caustic product containing bicarbonate. In doing this, you not only increase the pH, but also the nutrient solution’s pH buffer.
pH fluctuation with Aqua
infopaper-aqua_text_12.png
Influencing pH
Plants are capable of actively influencing the nutrient solution’s pH. If the intake of food is disturbed when the plants suffer a pathogenic attack, for example mould, it can cause the nutrient solution’s pH to drop below 3. Another symptom can be noticed with iron deficiencies and, in this case, the pH is actively lowered to make iron more available to the plants. For this reason, it is not advisable to have the same value for the pH continuously. With a good nutrient solution and a pH between 5.2 and 6.2 there should be no nutrient problems. If the pH should be lower than 5.0 or higher than 6.4 for a few days, it is advisable to carry out manual adjustments or to change the composition of the nutrient.
If Vega is being used and the pH drops too low during the twelve-hour cycle, changing to Flores nutrient is recommended (Flores is less acid; it is important to note that the plant now receives nutrient that is the best possible for its bloom). If the pH is too low, it increase with CANNA pH+ (Pro).
Douglas.Curtis
Autistic Diplomat in Training
Ok, that is very interesting. Thank you, englishrick. This is the first description from a nute company where I've seen advisement for a pH swing.
So nutrient solution composition has a lot to do with what the plants excrete.They excrete according to what they're missing, and/or in response to stress like mold. So my question is, what element is in higher demand once flower bulking quits? It will be in the elements available at lower pH, that's for sure. I'm thinking we need a third nutrient line, one for oil production. Veg, stretch and flower bulking, then switch to oil production.
As for the differences between osmotic and non-osmotic water and pH response, osmotic water users should have the buffer in the nutrients. Depending on tap water to have the proper amount of buffering is ridiculous, especially if you want to trade accurate information with other growers. Osmotic water users can trade reliable information with each other, while tap/well users (most often) have completely different water supplies.
This is the first description from a nute company where I've seen advisement for a pH swing. [/FONT]Canna said:
So nutrient solution composition has a lot to do with what the plants excrete.They excrete according to what they're missing, and/or in response to stress like mold. So my question is, what element is in higher demand once flower bulking quits? It will be in the elements available at lower pH, that's for sure. I'm thinking we need a third nutrient line, one for oil production. Veg, stretch and flower bulking, then switch to oil production.
As for the differences between osmotic and non-osmotic water and pH response, osmotic water users should have the buffer in the nutrients. Depending on tap water to have the proper amount of buffering is ridiculous, especially if you want to trade accurate information with other growers. Osmotic water users can trade reliable information with each other, while tap/well users (most often) have completely different water supplies.
Hydro8
Member
I have always considered fluctuations in the normal PH range the plants looking for food/a nutrient element.
Many plants I grow will stay steady in PH, I will set it at 6.0 with 550ppm and that will just keep going until I want clean nutrients. Then I will have plants(usually from the chem or OG family) that in flower after a few days will drop in PH, they will usually also be nutrient hogs and demand higher ppms.
I would imagine large professional grows are able to analyze the nutrients and create custom feed blends for certain strains. Instead of chasing PH or changing hundreds of gallons of nutrient they just add some iron(or whatever).
Many plants I grow will stay steady in PH, I will set it at 6.0 with 550ppm and that will just keep going until I want clean nutrients. Then I will have plants(usually from the chem or OG family) that in flower after a few days will drop in PH, they will usually also be nutrient hogs and demand higher ppms.
I would imagine large professional grows are able to analyze the nutrients and create custom feed blends for certain strains. Instead of chasing PH or changing hundreds of gallons of nutrient they just add some iron(or whatever).
Root secretions are definitely effective in moving ph,, canna aqua actual website says that if you see a pH drop it's an indicator to add pk 13/14,, i have used this pH drop indicator for years with fantastic success,, i add only enough pk to bring the pH back and I don't even check how many millilitres it takes as I just mix the tank and check the pH,,
Pathogens should really have been killed in cloning and surface sterilisation,, but it's not like I'm in the swing of doing this myself yet
If I ever need to solve any problems I just flush with water,, loads and loads of water,,, then I remix a tank (canna aqua) and run it,, then I check it progressively,, if pH drop is heavy il add pH and watch it rise,, that is actually my usual time and event when I'm forced to add pk/1314
Pathogens should really have been killed in cloning and surface sterilisation,, but it's not like I'm in the swing of doing this myself yet
If I ever need to solve any problems I just flush with water,, loads and loads of water,,, then I remix a tank (canna aqua) and run it,, then I check it progressively,, if pH drop is heavy il add pH and watch it rise,, that is actually my usual time and event when I'm forced to add pk/1314
I have had those same issues from time to time.
Things I've noticed about this, you have to ph you solution to a higher ph level as the solution will just keep dropping. If the solution keeps dropping from 5.6, raise it up to around 7. If it keeps dropping it should drop slightly slower.
I've noticed if you just try to bring it up to your desired ph range, it will just keep dropping back down to ph4. bringing you ph up to a higher level (7-8ish range) it then flip the direction the PH is moving. The ph will stay higher and then you can add some ph down to bring it back to your ph range.
The other 2 solution I've found that solves this issue is to add a gallon or two of tap water into your RO water, or by adding ph up into your RO water before you use it to mix your nutrient solution. It gives the RO some buffering to it's ph.
When I've had the same issue you mention, I don't like to keep adding more and more ph up into the solution. It adds some ppm
to the solution and it takes more and more and more each time to bring the PH back up.
Douglas.Curtis
Autistic Diplomat in Training
Very interesting. I would much rather add something the plant will be using, than some random tap/well water elements. This is the first time I've heard of using p/k this way. It makes a LOT of sense. And to think, I've had a jar of it around for years until about a year ago. lol Never used it much so I dumped it for the jar.
Hydro8
Member
I have been using GH 3-part, the Bloom is 0-5-4, Next time I get dropping PH I will try adding a bit of it.
