Questions for Al: calculating soil, dolomitic lime, etc
Could you please help me with a few questions and validate a few calculations? Thanks so much!
1) I am wondering about the correct amount of dolomitic lime for some very very large containers that I built out of 2x10s with plywood bottoms. The interior dimensions of these boxes are 21" x 45" x 19" deep.
If I calculate this into cubic yards, I get .38 cubic yards.
If I convert that into gallons, google gives me 76.7 gallons.
I have seen you say before that you use 1 TBSP/per gallon of soil, or 1/2 cup per cubic foot.
If I use the 76.7 gallons, I come up with about 4.8 cups. (OTOH, if I calculate it based on 10.26 square feet, I end up with 5 cups, so about the same.)
Does that sound right, about 4.8-5 cups of dolomitic lime for my large boxes, assuming they are filled to the top? (I suppose it jives with the ratios in the big batch you make of 33 gallons; my planters are about 2.5 times bigger than 33 gallons, and 5 cups is 2.5 times of 2.) But it just seems like SO much dolomitic lime. I'm worried about overliming.
2) How long does dolomitic lime live in the 5-1-1 mix or other soilless mixes? Will it continue to do its job for the life of the 5-1-1 mix? Or is it a relatively permanent addition to a container mix?
3) Is dolomitic lime something that needs to be mixed *into* the container mix, or can it work sprinkled onto the top? Here's why I'm asking: Some of my citrus are in a *modified* version of your soil. ;-) The peat component is from a potting mix that contained some lime, and so I didn't add additional lime last year when I mixed it up. After I have now read what feels like every post on here I could find about dolomitic lime, I realize how important it is in the pH of a bark-based potting mix, and I also realize in hindsight I probably *should* have either added more lime or *not* have used that bagged mix and used straight peat. Oh well... lesson learned for next time.
Anyway, what I'm wondering about now is whether I can put the dolomitic lime on top of those containers (if not in its total amount, then maybe a sprinkling)... either on top or worked into the top of the containers. And in what quantity or ratio.
And finally, a question about adding dolomitic lime to Mel's Mix (of SFG fame)... but feel free to disregard this part of the question if you just don't want to deal with the relative merits/structure of that mix. I would understand. :-)
4) My very rudimentary understanding of why one would add dolomitic lime is because the bark fines contain such a low pH? Do you know (or would you guess) at the possible pH of Mel's Mix and the proper dosing (if any) of dolomitic lime to such a mix? I'm just wondering, in a mix like that with more peat and Vermiculite (which are more ph Neutral) and compost, which is only slightly acidic, would you still use dolomitic lime? And if so, in what ratio? I do use Mel's mix for some of my containers and it works fine for me, and it gets refreshed each year with bark fines and composted plant matter. I'm just wondering if dolomitic lime might be appropriate to add at this point to help pH and micronutrient uptake.
Thanks so much for your advice and guidance, Al.