Thanks for the info Tom.
Currently i am adding about .5ppm of urea a day at one dose. Really the goal is to not provide faster growth, but larger growth(leaves/whirls). So far i have not seen much in a positive or negative way, but i just started....so a few weeks of consistency is in order before i am comfortable saying one way or another. I will certainly report my findings after i am done.
BTW, I estimated using mass balance ratios for NH$ uptake rates max per day, I think I came up with a max of 0.8ppm of NH4 per day max usage.
Note: your bio section is FAR more aggressive with NH4 and urea than it ever was with the much more difficult NO3
. The oxidizing bacteria are very quick and many are likely just growing more bacteria to large degree, and that, is one reason you are not seeing more plant growth.
NO3 is much harder to attack and remove via bacteria.
NH4/urea is much more ephemeral.
I know a feller who dosed pure NH4 to his tank daily, adding about the suggested amount I gave, 0.8ppm, he had good growth, though not that much better one way or the other.
But he did daily 80% water changes, blah, way too much work etc.
He stopped for a weekend and got green water.
I think small amounts of NH4 are fine and adding more fish does the trick there. They dose at low levels all the time, so that is more practical/safer.
Main thing is being consistent.
You add for awhile, then stop, then resume, be prepared for issues.
Bacteria colony build up takes some time but can be fairly responsive(or not if things like say CO2 are not addressed well etc or go sour).
I think what we are seeing is mainly bacteria, the rates of uptake, see the graph, are not that high at the ppms we add if NO3 is also present.
Bacteria are better at lower levels general if they are consistent.
The study she used had no bacteria in the test.
So that is big issue to apply here in our situation, we have bacteria and they use NH4. The other issue is the plant adaption prior to the short test. you can adapt plants to various routines.
As fas as larger growth, eg larger leaves etc, less light produces consistently larger leaves. As long as less light is not from shading by other plants, this works well.
If you make the assumptions about NH4/urea, then you can also assume we should similar results in the sediments as well.
Eg ADA AS, sand+ soil and so forth.
I really do not see it there either.
Again, bacteria, plant roots+ O2, tend to convert a fair amount into NO3. In agriculture, they try hard to keep in NH4+ forms, but water + urea etc, = NH4 fast and it loses about 50% to NO3 in most soils.
So if we lost 50% of the urea/NH4, that's a fair amount vs the study she used to support.
It's not so dang simple as many like to suggest and is real issue in other areas. I do not think it's that big of a deal for us though.
At least nothing I've seen or test suggest it does, I'll be happy to try something to see though.