SO4 as Sulfur Fertileser?

[Science]

Hi,

Will plants use SO4 (in MgSO4 or K2SO4) as a sulfur source?

thanks,

[FC]

Emre,

I believe so (I do not have the test kit to measure SO4) because plants take up NO3 from KNO3, PO4 from KH2PO4, etc. However, I suspect that plants do not consume much SO4 in KSO4 form. Why are you asking about SO4? I asked because nobody seems to care about this nutrient although it is an important macro.

[Science]

Thanks Freddy,

Since I am dosing separate chemical powders as fertilisers, not aquarium products, I don't want to skip this macro. I also wonder where all that SO4 ions (from MgSO4, K2PO4) are going. Maybe they are building up?

All the best,

[FC]

I think so.

About a year plus ago, there were hot discussions in forums on excess K+ in tank that lead to several problems. I think K+ was not the culprit but the built up of the SO4 is. Since then, many had depend KNO3 for both K+ and NO3. And best part of all, KNO3 was found to have more than sufficient K+ (vs NO3 it contain) to go around. My tank hardly need KSO4, I use in very very small amount. As for SO4 dose, you can rely on MgSO4, forget about SO4 you will get from it (it has very high SO4 content, more than enough), just dose to get about 2 ppm of Mg concentration.

[TyroneGenade]

Hello,

Mg is a micronutrient greatly in demand by actively growing plants. K is macronutrient that is always in great demand. S is also a micronutirent but vast amounts normally come into the tank via fishfood etc...

A minor dosing with MgSO4 should do very little harm but be careful. Bacteria will reduce the SO4 to H2S in anoxic sections of the substrate. As long as you do not add vast amounts of SO4 this is umimportant but something to keep in mind.

Dosing with KNO4 should be an OK way of giving both K and N. The NO4 will also be reduced in the substrate to either N2, NO2 or NH3?NH4 which the plants will take up long before it become toxic. Aerobic bacteria will take care of any residual NO2.

Regards

[fabry]

Hi Tyrone.
Do you maybe mean KNO3 (Potassium nitrate)?

KNO4 should be potassium peroxynitrate (salt of Peroxynitric acid - HO2NO2).
Peroxynitric acid is a molecule whose chemistry is not fully understood yet.
We know for example that it is a very powerful oxidant that is formed in the atmosphere by the combination of hydroperoxy radicals and nitrogen dioxide:

HO2 + NO2 -> HO2NO2

I do not think it would be suitable as a supplement for aquariums.

Regards.

[TyroneGenade]

Do you maybe mean KNO3 (Potassium nitrate)?

Yes, sorry. Big slip-up there. Was a bit in a rush when I wrote that and didn't have time to check over my writing. KNO3 it is supposed to be.

Sorry for my ineptitude.