Mixing my own ferts

Hey all, looking to mix my own fertilisers for a hydro system, but I need help.
So far, I've got two formulas, one for vegetative, lots of nitrogen:

One part ammonium phosphate, one part potassium nitrate (saltpetre/saltpeter) and one part urea
Which gives an NPK rating of 30-16-16

And another for during budding:
One part ammonium phosphate with one part potassium sulfate (sulphate of potash)
Which has an NPK of 14-24-27

I recon the NPKs are pretty good, but there are no trace elements or magnesium in the mixture. Can anyone suggest how much magnesium sulfate (epsom salts) and this trace element mix to add: http://www.gardendirect.co.uk/chelated-trace-element-mix-p-887


Cheers!

YourUsernameHere said:

Hey all, looking to mix my own fertilisers for a hydro system, but I need help.
So far, I've got two formulas, one for vegetative, lots of nitrogen:

One part ammonium phosphate, one part potassium nitrate (saltpetre/saltpeter) and one part urea
Which gives an NPK rating of 30-16-16

And another for during budding:
One part ammonium phosphate with one part potassium sulfate (sulphate of potash)
Which has an NPK of 14-24-27

I recon the NPKs are pretty good, but there are no trace elements or magnesium in the mixture. Can anyone suggest how much magnesium sulfate (epsom salts) and this trace element mix to add: http://www.gardendirect.co.uk/chelated-trace-element-mix-p-887


Cheers!

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Theres a mixture called Azomite that would answer all your trace elemental needs. Google it I use it as a tea in hydro and as an amendment in soil. On epsom using 1/2-1 tsp per gallon is the norm. Mag should be at a 1 to 3 ratio to calcium.

Badmf said:

Theres a mixture called Azomite that would answer all your trace elemental needs. Google it I use it as a tea in hydro and as an amendment in soil. On epsom using 1/2-1 tsp per gallon is the norm. Mag should be at a 1 to 3 ratio to calcium.

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Hmm, cant find it anywhere. But i found a typical analysis of it, so I can work out how much i'd need of the trace element mix.
I heard that Ca2+ is toxic to the cannabis family, to such an extent that you cant feed your plants tap water. Is this just pseudoscientific junk?

Too much Ca2+ will displace other micros, but its pretty damned important actually..
Amoniacal N isn't used to a great extent in most hydroponic systems due to lack of organic matter for NH4+ to bind with, thus allowing loss as NH3(g)..
And Urea isn't effective in hydro either due to lack of microbes to break it down..
All in all I think you should research a bit.. At this point micros are the least of your worries..

born2killspam said:

Too much Ca2+ will displace other micros, but its pretty damned important actually..
Amoniacal N isn't used to a great extent in most hydroponic systems due to lack of organic matter for NH4+ to bind with, thus allowing loss as NH3(g)..
And Urea isn't effective in hydro either due to lack of microbes to break it down..
All in all I think you should research a bit.. At this point micros are the least of your worries..

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Hmm, I see.... So it all has to come as [NO3]-? I thought the plants themselves would be able to absorb [NH4]+ and (NH2)2CO... Do they only get metabolised in the soil then?
So the main ions I'm going to need will be [PO4]3-, K+ and [NO3]-.... Thats going to leave me with a lot of negative charges... How do people usually get around that?

Plants can uptake NH4+, but in hydro its really hard to keep it in the res long enough to do so.. And urea primarily ends up converting to NH4+ with the assistance of microbial life.. In our pH range though, NH4+/NH3 ratio likes to too far to the NH3 side which dissipates too readily as gas.. NH4+ likes to bind with soil matter thus holding it in place.. You're dealing with the same problem farmers face with N loss but to a much greater degree..
So yea hydroponics really leans toward the nitrate form of N..

born2killspam said:

Plants can uptake NH4+, but in hydro its really hard to keep it in the res long enough to do so.. And urea primarily ends up converting to NH4+ with the assistance of microbial life.. In our pH range though, NH4+/NH3 ratio likes to too far to the NH3 side which dissipates too readily as gas.. NH4+ likes to bind with soil matter thus holding it in place.. You're dealing with the same problem farmers face with N loss but to a much greater degree..
So yea hydroponics really leans toward the nitrate form of N..

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Hmm I see.... But that means I'll need a lot of [NO3]- at first... What cation can I balance it with? Should I just use KNO3 and K3PO4? It'll leave me with a huge excess of K+ though....

Some Calcium nitrate perhaps, no real problem with ammonium nitrate if you can get it without DHS busting your grow, In hydro that would equate to pretty much pure nitrate, as would nitric acid.. (Nitric acid will kill you in a couple days very painfully if you breathe strong fumes..)
Really hydroponics fertilizers are dangerous to produce without proper knowhow, and dangerous to obtain reagents to create in this day and age.. Besides you'd need some decent chem background and apparatus to keep equilibriums in check and avoid unwanted byproducts..

born2killspam said:

Some Calcium nitrate perhaps, no real problem with ammonium nitrate if you can get it without DHS busting your grow, In hydro that would equate to pretty much pure nitrate, as would nitric acid.. (Nitric acid will kill you in a couple days very painfully if you breathe strong fumes..)
Really hydroponics fertilizers are dangerous to produce without proper knowhow, and dangerous to obtain reagents to create in this day and age.. Besides you'd need some decent chem background and apparatus to keep equilibriums in check and avoid unwanted byproducts..

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I'm kinda ok at chemistry... I'm really interested in it and I have a little lab in my back garden
By "avoid unwanted byproducts" do you mean precipitation reactions and suchlike? Eg:
Ca(NO3)2(aq) + MgSO4(aq) ---> CaSO4(s) + Mg(NO3)2(aq)

Come to think of it, this does sound like more effort than its worth.... I can get hold of ammonium nitrate, but I think I'll probably be easier just to buy ready-made stuff...

I'm not entirely sure that would be an undesirable one..

born2killspam said:

Ouch.. Well it was fun while it lasted... See ya later..
Although I'm not entirely sure that would be an undesirable one..

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Wouldnt it be? I'd have thought if you had insoluble calcium sulfate, that'd decrease the availability of calcium and sulfur... Well do you think my original formulas would work in a soil growing system? Caause I'm thinking I might grow a couple of plants in soil too...

Calcium and Sulfur are micros remember too much is bad..

Its a good start for soil, although I'd never let K exceed P during flowering unless I was growing outside in a really harsh climate.. Don't expect to not have to tinker with things after results are apparent.. Hopefully Uncle Ben will pop in here, he's a master with salt management.. He's proof that walmart and the farming community etc can help you do the job as well as the hydroponics store..

born2killspam said:

Its a good start for soil, although I'd never let K exceed P during flowering unless I was growing outside in a really harsh climate.. Don't expect to not have to tinker with things after results are apparent.. Hopefully Uncle Ben will pop in here, he's a master with salt management.. He's proof that walmart and the farming community etc can help you do the job as well as the hydroponics store..

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Ah right, thanks. Ill probably lay off the K2SO4 a bit then, or maybe add some more (NH4)3PO4

There are different schools of thought on that too.. UB and I hold to what I said, but alot of K helps plants look pretty even under a fair bit of abuse.. Thing is its supposed to be about flower production, and that is the job of P in the basic sense.. I'd make the analogy that a plant fed too much K during flowering, is like a guy who spends too much time in front of the mirror when he could be getting more shit done..
Those fandangled AN products etc seem to have a HELL of alot of K in them.. I know hydroponics in general isn't as comfortable for a plant as nice healthy living soil, but I really think yields could improve if they cared less about appearances and lowered that.. Of course the plant may not be as resistant to moderate mess-ups, and they'd lose alot of their target customers..
To summarize the basics: (Although everything overlaps as well)
N - Green Growth
P - Flowers & Roots
K - Resistance & Sturdiness (but at a moderate price if too abundant)

Then the micros.. I know the hydro store here carries a micro blend as well as a few raw salts.. I'd just buckle and look for something like this because they're complex and tricky, and typically require chelating agents..
Lastly, something that is rarely mentioned is Silicon.. This can do alot as far as strength & vigor goes.. Most soil is abundant with it, but if interested in addition of it and bioavailability read up on silicic acid..

born2killspam said:

There are different schools of thought on that too.. UB and I hold to what I said, but alot of K helps plants look pretty even under a fair bit of abuse.. Thing is its supposed to be about flower production, and that is the job of P in the basic sense.. I'd make the analogy that a plant fed too much K during flowering, is like a guy who spends too much time in front of the mirror when he could be getting more shit done..
Those fandangled AN products etc seem to have a HELL of alot of K in them.. I know hydroponics in general isn't as comfortable for a plant as nice healthy living soil, but I really think yields could improve if they cared less about appearances and lowered that.. Of course the plant may not be as resistant to moderate mess-ups, and they'd lose alot of their target customers..
To summarize the basics: (Although everything overlaps as well)
N - Green Growth
P - Flowers & Roots
K - Resistance & Sturdiness (but at a moderate price if too abundant)

Then the micros.. I know the hydro store here carries a micro blend as well as a few raw salts.. I'd just buckle and look for something like this because they're complex and tricky, and typically require chelating agents..

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Aha, I see. Thanks for the explaination I probably will lay of the K2SO4 a bit for the flowering mix then. Its already got plenty of P though, so that should be fine. I've never really understood what the biological role of K+ is in plants... I know nitrogen's found in proteins and amino acids, phosphorus in the deoxyribose-phosphate backbone of DNA, sulfur in amino acids eg cysteine, Mg in chlorophyll.... But K's never made sense.

Its actually more of an assistant ion.. It assists in carbohydrate translocation, and it helps other nutrients do their jobs better, and allows a plant to thrive with lower nutrient levels overall.. Thing is it helps nothing more than N.. And I'm sure you've read that too much N late in the game can inhibit/slow flowering.. This was my point about keeping it low unless climate stresses are high..

born2killspam said:

Its actually more of an assistant ion.. It assists in carbohydrate translocation, and it helps other nutrients do their jobs better, and allows a plant to thrive with lower nutrient levels overall.. Thing is it helps nothing more than N.. And I'm sure you've read that too much N late in the game can inhibit/slow flowering.. This was my point about keeping it low unless climate stresses are high..

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Ahh, I see. So does that mean I should ideally be starting with high NK, low P, then switching to high P, low NK; rather than starting on high N, low PK then switching to high PK, low N?

Pretty much, although hungry seedlings and small clones do like a short stint of some decent P.. For that matter they also tend to prefer more ammoniacal N in that time frame too.. Take a look at some transplant fert's MSDS's.. Hell look at any and all MSDS you can get your hands on,,

born2killspam said:

Pretty much, although hungry seedlings and small clones do like a short stint of some decent P.. For that matter they also tend to prefer more ammoniacal N in that time frame too.. Take a look at some transplant fert's MSDS's.. Hell look at any and all MSDS you can get your hands on,,

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MSDS, brilliant! I should have thought of that - MSDSes are so revealing
I found a ferric chloride stain remover once and it was really expensive - about 14 quid for a hundred grams. Had a quick look in the MSDS, and voila - 98-100% oxalic acid. 9 quid a kilo on ebay.