I use mix mith 8qt peat moss + 8qt perlite + 8qt vermiculite. How much dolomite lime I have to add to this mix?????
it depends. The more alkaline is your water - the more you need dolomite lime. People who have well water - they already have too much of it. It usually depends on the climate - more rain in your area - like on the East coast - more lime you need.
Here is a link that might be useful: several recipes
This is a late post, because I was just searching to see what others were doing when adding dolomite lime to their peat mix, but I recently purchased a pH meter and tested my Sphagnum Peat and found it to be 3.66 pH. I have slowly added small amounts of lime over a period of several days to a seven quart sample of Sphangum Peat to try and get the pH into the 6.7-6.9 range, and I have found that I have needed to add a little over 2 Tbs per quart of Peat (15 Tbs for my 7 quart sample)) to get it into the 6.5 range. However, from what I understand not all sources of peat will have the same pH, so you would probably need a pH meter to tell for sure, but adding 1-2 Tbs per quart of Peat would probably be a good start. Let it sit a day or two, and check the pH again, because the lime takes a while to act. I have been using the powdered dolomite lime and not the pelletized dolomite lime. The finer powdered lime will act a little faster in neutralizing your peat.
You are doing everything very right!
You just need to check your recipe for 6 more months when your plants are sitting in the same soil.
the idea is to add crushed lime - the fine particles neutralize the peat now, the larger particles work slower and neutralize it when peat moss starts to decompose and create more acid. Amount of the lime will depend on what is the acidity/alkalinity of your water - if it is alkaline - your soil will keep from oin acid longer. If you use rain water or RO water or your tap water is acid - you can consider adding more coarse dolomite for the long going solution.
So your PH meter is very handy to fine tune your recipe for your home and make your violets grow like out of this world.
Thanks for the tip, Irina. I have tested the pH of my potting mix in plants that were 4-5 months old vs. the pH of the mix in freshly potted plants and found that the older potted plants were in a mix that was only slightly more acidic than the freshly potted mixture. Since it is recommended that African violets be repotted about every 6 months, I don't think that adding additional coarse dolomite to a new mixture that is in the 6.5-6.9 pH range would prove beneficial. The problem that I see in adding the additional coarse dolomite is that one would not know exactly how much of the coarse dolomite to add to the mix, and if you added too much it could cause your pH to rise above 7.0 and higher, which may cause your potting mix to be way too alkaline. I would rather address the issue of Peat becoming slightly more acidic over time by repotting on a regular schedule into a mixture of the proper pH.