the above is calculated based on US 50 gallon or 189.27 liters. it is not based on Imperial gallons.@Happi - can you please clarify if the dosage per gallon you refer to is Imperial Gallons or US gallons as that will affect the dosage ( I have dosed as if UK Imperial gallon but now have doubts)
My tank is nominally 340 litre so thats roughly 75 Imperial gallons - I have been dosing 30ml of Solufeed 2:1:4
after looking at your water report, it seems like PH is bit on the higher end. Darrel has already given you a great answer regarding your water report. if you had a acidic soil, your PH would be lower than 7.please cast your eyes over the above and enclosed water quality report for my zone and let me (and the others on this forum) know if you can foresee any pitfalls that I may be heading towards with my intended approach (especially @Happi regarding the imperial/US gallon issue)
anyway, some member are still comparing the Urea and Ammonium being the same thing and seems to be creating a fear about using it, i repeat that Urea and Ammonium/Ammonia works in a entirely different manner. you can successfully use urea even in a PH that is higher as 7, but it is advised to use it in lower PH where Ammonia will stay in its less toxic form Ammonium.
the best way i could put this is, think of Urea as a osmocote pellet, where the Ammonium is released very slowly. it does the same thing in the solution, as it slowly start to convert into NH4.