lime, cal/mag ratio, and base saturation rate
I'm trying to get all this information straight in my head so I was hoping for some help. For containers I prefer to grow organically in a peat based mix and so adding something to raise the pH is necessary. I've learned that in lime it is actually the carbonate that raises the pH. So two of the common choices are either calcium carbonate (calcitic) or calcium magnesium carbonate (dolomite).
I understand that for a garden outdoors adding dolomite should only be done when you need to raise the pH, calcium level, and magnesium level. Calcium carbonate is used when the pH and calcium needs raised but the magnesium levels are ok. And gypsum can be used when the pH and magnesium are ok but the calcium needs raised.
So in container growing I am responsible for adding everything that the plant needs. I understand there is one school of thought that says a specific cal/mag ratio needs to be obtained. But i have also seen a number of studies that show various ratios can be used as long as there is adequate levels of both minerals.
The next concept is the base saturation percentage. This is simply the percentage of exchange sites occupied by cations. So say you want a cal/mag ratio of 7:1, is that the same as calcium having a base saturation percentage of 70% and magnesium having 10%? And if the importance of a cal/mag ratio is disproved then does that do the same for trying to get a specific base saturation level?
Now say in my containers I use dolomite as my only source of lime (as many seem to do). This is a cal/mag ratio of around 2:1. Is there any advantage to using a mix of half calcium carbonate and half dolomite? Or 1/4 calcium carbonate and 3/4 dolomite? This would raise the cal/mag percentage higher.
It is also my understanding that the magnesium in dolomite is much more soluble than the calcium, is this correct? That is why i was wondering about using something in addition to dolomite. I understand that things like crab meal also contain calcium carbonate. Is there any difference in the time of availability between different calcium carbonate sources or are they pretty much the same?
Basically what it comes down to is that i want to make sure that the plant gets adequate amounts of calcium and magnesium. I have always used dolomite but am now wondering if there is a better way? Or as long as i have enough dolomite to cover the calcium and magnesium needs is that enough?
Thanks for any help and taking the time to read this