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DIY all in one fertiliser solution going cloudy

Rapayich

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I have been messing around with making my own all-in-one fertiliser mix over the past few months but can't seem to get it right. In my solutions I am using:

KNO3
KH2PO4
MgSo4
DTPA Iron 11%
Copper sulphate (Unchelated)
Manganese sulphate (Unchelated)
Boric Acid (Unchelated)
Zinc Sulphate (Unchelated)
Sodium Molybdate (Unchelated)
Potassium Sorbate
Ascorbic Acid
RO Water

Before adding the salts I ensure the water has been acidified to about 2.5pH. I also ensure that the macro and micro solutions are fully dissolved before combining. The solution remains clear for about 2 weeks but then goes cloudy. Note that no precipitate can be seen but it definitely goes cloudy throughout the whole solution. Does anyone have suggestions regarding this issue. Maybe the cloudiness is not a problem and is moreso some sort of bacterial buildup? My RO unit is very old but can still produce water around TDS 5. Solutions are kept at room temp and in a dark container away from sunlight.

Cheers!
 

Rapayich

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I'm glad you posted this, the same thing happens to my solution!

View attachment 197310
(New clear batch)

View attachment 197311
(Cloudy batch)

My plants don't appear to be affected as far as I'm aware but I've noticed this. The mixture doesn't smell bad either, does yours?
Just had a thought on this. Is the fertiliser bottle exposed to sunlight at all? (even indirect) The chelated may be breaking down and causing the clouding.
 

Hanuman

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@Courtneybst Thank you. I replicated your formula in the IFC calculator and didn't see any major solubility issue. The only thing that is a problem IMO is the fact that you are using a sub 10% chelated iron. To that, add the fact that APFUK also uses an 8.2% EDTA chelated iron. Try using a higher % chelated iron like 11%. It is possible that the 8% you are using is driving the PH up and allowing a reaction to happen. At least that's what I experienced in the past. That's why I only use and advise anyone to use 11% which additionally will also drives your PH down which is a good thing.

Hmm maybe some of the trace elements are not chelated allowing for bacteria to feed on them or precipitate to occur. Just a guess 🤔
No. I and many others use unchelated traces with no issues.
 

Rapayich

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@Courtneybst Thank you. I replicated your formula in the IFC calculator and didn't see any major solubility issue. The only thing that is a problem IMO is the fact that you are using a sub 10% chelated iron. To that, add the fact that APFUK also uses an 8.2% EDTA chelated iron. Try using a higher % chelated iron like 11%. It is possible that the 8% you are using is driving the PH up and allowing a reaction to happen. At least that's what I experienced in the past. That's why I only use and advise anyone to use 11% which additionally will also drives your PH down which is a good thing.


No. I and many others use unchelated traces with no issues.
I thought you had some issues with clouding when using unchelated traces in the ‘higher’ concentration solutions? After a month or two.

Possibly the chelation of these traces would allow how concentration solutions to last much longer?
 

Hanuman

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I thought you had some issues with clouding when using unchelated traces in the ‘higher’ concentration solutions? After a month or two.
Where did I say that?
In fact what I said above is that my current batch, which is 3 months old, is still clear.
We are doing DIY ferts in a home environment with DIY processes. It's not like in a factory where everything is controlled and were they also add certain agents to stabilize the fertilizers for years. As mentionned by @Happi, maybe you could try sodium benzoate instead of ascorbic acid.
If you wish to have long term ferts I would suggest buying commercial products or the other alternative is to separate macros and traces. Another solution would be to make larger amounts and freeze what you don't need.
 
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Rapayich

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Where did I say that?
In fact what I said above is that my current batch, which is 3 months old, is still clear.
We are doing DIY ferts in a home environment with DIY processes. It's not like in a factory where everything is controlled and were they also add certain agents to stabilize the fertilizers for years. As mentionned by @Happi, maybe you could try sodium benzoate instead of ascorbic acid.
If you wish to have long term ferts I would suggest buying commercial products or the
Where did I say that?
In fact what I said above is that my current batch, which is 3 months old, is still clear.
We are doing DIY ferts in a home environment with DIY processes. It's not like in a factory where everything is controlled and were they also add certain agents to stabilize the fertilizers for years. As mentionned by @Happi, maybe you could try sodium benzoate instead of ascorbic acid.
If you wish to have long term ferts I would suggest buying commercial products or the other alternative is to separate macros and traces. Another solution would be to make larger amounts and freeze what you don't need.

other alternative is to separate macros and traces. Another solution would be to make larger amounts and freeze what you don't need.
I think it was in another thread. This one I think.

Also I checked the fert calc and it suggests making more dilute or smaller batches. I may have misinterpreted.

I’ll definitely be giving the benzoate a try along with chelated traces.
 

Hanuman

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I think it was in another thread. This one I think.

Also I checked the fert calc and it suggests making more dilute or smaller batches. I may have misinterpreted.

I’ll definitely be giving the benzoate a try along with chelated traces.
Oh yes I thought you meant in this threat.
Definitely it is recommended to do more dilute batches. This said and I'll repeat again, you don't need to use chelated traces but up to you. I'll cost you more that's for sure.
 

Rapayich

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Oh yes I thought you meant in this threat.
Definitely it is recommended to do more dilute batches. This said and I'll repeat again, you don't need to use chelated traces but up to you. I'll cost you more that's for sure.
Thanks for all the help Hanuman and great work on the calc :)
 

Courtneybst

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@Courtneybst Thank you. I replicated your formula in the IFC calculator and didn't see any major solubility issue. The only thing that is a problem IMO is the fact that you are using a sub 10% chelated iron. To that, add the fact that APFUK also uses an 8.2% EDTA chelated iron. Try using a higher % chelated iron like 11%. It is possible that the 8% you are using is driving the PH up and allowing a reaction to happen. At least that's what I experienced in the past. That's why I only use and advise anyone to use 11% which additionally will also drives your PH down which is a good thing.


No. I and many others use unchelated traces with no issues.
Thank you so much! That's super helpful. I'll order some 11%. Do you think this reaction could cause some of the Fe to become unavailable for the plants at all? I don't really have any major plant issues except the old holey leaf in some Bucephalandra.

Also sorry @Rapayich for hijacking your thread!
 

Hanuman

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Thank you so much! That's super helpful. I'll order some 11%. Do you think this reaction could cause some of the Fe to become unavailable for the plants at all? I don't really have any major plant issues except the old holey leaf in some Bucephalandra.

Also sorry @Rapayich for hijacking your thread!
Not being a chemist, I can't tell you for sure what reaction is happening (could be a phosphate-Fe reaction) but no matter which reaction it is, the fact that you have a precipitate means that the newly formed compound is insoluble, which in turns means it can't be used by the plants. You shouldn't use a solution that has precipitated out.
 

dw1305

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Hi all,
For some reason I had assumed that DPTA 11% would do the same as DTPA 7% but to a lesser degree. This is an eye opener and the PH drop was rather significant.
I think it will be because the 7% DPTA will <"have another metal chelated"> and <"that metal is almost certainly sodium (Na)"> and Na <"is an alkaline (group 1) metal">.
You can make an iron EDTA solution (using the sodium EDTA salt and iron sulphate), but you can also buy iron EDTA as the monosodium ferric salt (C10H12FeN2NaO8). Sodium (Na) is the least strongly bound element and Iron (Fe) is the most strongly bound one, so you can make any other chelates from the sodium salt, but once you have FeEDTA you can't bump the iron off (it photo-degrades to release ferric (Fe+++) ions in the tank).

cheers Darrel
 

Happi

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Dear Members,

if you were to use DTPA Fe 11%, it will lower the PH to desired levels and you do not need to add Ascorbic acid or anything else to acidify the solution. you will only need to add some preservative if you want the solution to last for years, but it would be wise to make the solutions that only last few months.

When DTPA Fe 11% is combined with the other unchelated salts, the solution should be much clear and long lasting. i must say that it is even more clear and longer lasting compared to if the solution was made with DTPA Fe 11% and other EDTA salts combined.

when DTPA 11% Fe and Unchelated salt are combined together. the entire solution is rather Semi Chelated but with much better Chelate in the form of DTPA. under such scenario DTPA will try to grab and chelate other metals as well.
 

Hanuman

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@Happi
I see 2 drawbacks with the above procedure though:
1. One would need to add the iron 11% first to acidify the water before adding other compounds. This is not ideal since it makes it difficult to see any potential precipitate that might happen during the addition of subsequent compounds. This is why @X3NiTH advises adding it at the end.

2. One can only use 11% Fe or above or chelates that do not bring the PH up. In the case of @Courtneybst he is also using APFUK traces which contain 8% and will raise the PH.

This is why we always advise in the IFC calculator in acidifying the water prior adding anything and why ascorbic acid is recommended. This said your way is an alternative and could be used in certain case scenarios.
 
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