MikeInOz wrote: ↑Fri May 24, 2024 3:57 am
That is not my experience. Nitrate is inferior to ammonium in some situations and can cause yellowing rather than greening. For example plants which need acidic soil conditions may do not do well with nitrate. This includes many cacti of course. For example, Gymnocalycium, Notocactus, Echinopsis, Rebutia, many cereus, Parodia, Probably Copiapoa, plants from Baja California and other volcanic soils and on an on.
This is news to me. I have many of the cacti you listed (Notocactus schlosseri, Notocactus Haselbergii, Parodia leninghausii, Echinocereus rigidissimus, etc) all currently in acidic soil around 6 pH (don't most cacti prefer acidic?). To confirm, they will not do well with a fertilizer that has majority nitrate for example in say a 3:2 ratio? Are you able to share why that is exactly and if it's dangerous to provide any nitrate to them over the long term?
I should have elaborated by saying that most plants from acidic substrates prefer ammonium over nitrate and that all nitrate N can cause yellowing because over time the nitrate fertilizers such as calcium an potassium nitrate tend to raise pH. Also, some of these plants seem to not utilize nitrate as well as they do ammonium. Eg, many commercial orchid growers have found nitrate to be a disaster for their plants over time. It caused a kind of chlorosis. We just need to be aware of these things and judge the results by observing the plants.
Steve Johnson wrote: ↑Fri May 24, 2024 8:28 am Generally speaking, North American species are ev0lutionarily adapted to alkaline soils,
I think that these soils would be more neutral than alkaline with a pH of around 7. Even if growing in pure limestone from what I have read.
Yes, that's right. In fact, in my area most igneous rocks (which are generally thought to be acidic) have much higher pH than limestone or dolomite (e.g. basalt from the local quarry has pH up to 9). I also noticed that people consider gypsum to be very alcaline while it's in fact slightly acidic. On a packaging of food grade gypsum (calcium-sulfate dihydrate) (E516) that I recently bought (after Mike sugested that I should add it as a soil amendment - excellent source of calcium and sulphur), it is written: "It is used to correct mineral deficiencies in the water used for brewing beer. Used for lowering the pH level (by increasing acidity). It is used in de-mineralized or soft or medium hard water to increase the permanent hardness of the water."
