George Farmer said:
plantbrain said:
But lower KH is better in all cases I can think of for plants.
Why is this exactly? I've suspected this myself but don't know why...
Likely has to do with uptake of CO2 and enzymatic efficiency. As the carbonate alkalinity increases, the efficacy seems to decline. I do not think this has anything to do with other nutrients though.
The growth of so called low KH soft water plants in high KH seems to mimic poor CO2, not N, P, K, Fe deficiencies.
If higher KH's blocked say N, or P, we should be able to add more or limit them in soft water tanks and illicit the same growth responses.
Only CO2 seems to do this with these plants.
I can take a plant and add poor cO2/not enough and get the same slow death/poor growth on say S "belem" in Soft low KH, say 1 degree....................as I can trying to grow it at 11 KH. I cannot do this with NO3, or PO4, or Fe.
When BOTH systems are enriched with non limiting CO2, then only the KH is the independent variable..........we still have CO2 like growth issues on this group of plants.
Other species are unaffected however, so it's selective. Most of these softer water species are poor competitors for CO2 and tend to have higher CO2 demands as well vs other plant species also. Without a labeling experiment using 14CO2 or something, it is tough to say where and what is going on with the CO2 uptake enzymes and intermediates.
No one has compared suspected soft water tropical plants we have trouble with growing at higher KH vs the low KH I am aware of using non limiting CO2 gas enrichment.
It's sort of highly specific question and not something botantist will study really since it's not a natural system and tropical rare aquatic plants are under the radar.