The Virtues of Dolomite Lime

[MrFista]

A minute - LOL.

We can start on it in a minute. Anybody got the pKa of dolomite. Also, any chemists wanna help, this equilibrium might get tricky.

Citrate molecule (C6H8O7) looks to be polyprotic - able to donate more than one hydrogen. From where I'm sitting - 3 of them. 3 -OH groups attached to C=O groups making them acidic.

Overall the equation should resenble this

4 C6H8O7 + 3 CaMg(CO3)2 -> 4 C6H5O73- + 3 Ca++ + 3 Mg++ + 6 H2CO3.

The pKa for citric acid is 3.13. Pka for carbonic acid (conjugate acid H2CO3) is 6.37. As the pKa of the reactant acid is higher than the product acid this reaction will proceed until the citric acid is consumed completely and excess dolomite is present. A start...

If the acid is not triprotic (donates three protons) the above is wrong.

Assuming I've half a clue. Chime in if I'm wrong! I'm reviewing acids/bases right now so it's convenient to do this stuff I'm not 'really' avoiding study he.

M [C6H8O7] = 192.124g mol L-1.
M [CaMg(CO3)2] = 184.41g mol L-1.

 

[MrFista]

Bit tricky with two species, easy with just the acid/conjugate base pair. With acid/conj base and base/conj acid.... Trickier than I first thought. (pulls very large head in).

Some more info to help get to bottom of it.

Citric acid has 3 levels of dissociation as I suspected, this also gives 3 pKa values.

pKa 1 = 3.128. C6H8O7 + H2O -> C6H7O7- + H3O+

pKa 2 = 4.761. C6H7O7- + H2O -> C6H6O7-- + H3O+

pKa 3 = 6.396. C6H6O7-- + H2O -> C6H5O7--- + H3O+

Carbonic acid, which appears in products (conjugate acid) has two levels of dissociation

pKa 1 = 6.352. H2CO3 + H2O -> HCO3- + H3O+
pKa 2 = 10.329. HCO3- + H2O -> CO3-- + H3O+

Now then, what pH do you require sir?

 

[VerdantGreen]

thanks mr F. this is stretching my chemistry knowledge to (and perhaps beyond) it's limit.

this may also be relevant in the citric acid thread i just started?

VG

 

[MrFista]

No worries VG I'll move over to that thread.

1. I need help with this my software is spouting gibberish.

2. The thread starter wanted a lime thread without math and chem. Building sandcastles perhaps.

 

[SupraSPL]

I also started a thread because I am having cal mag issues thanks to a more powerful veg lamp. I finally got an R/O machine and a ppm meter so I experimented using peat acids to dissolve the dolomite. It seems to work fine but surprisingly carbonic acid seems to work just as well and without the mess of peat.

Just add R/O water + dolomite lime (rinse thoroughly if coated) then exhale into the jug several times and shake. The pH will drop as far as 4.5. I was able to raise the ppm from 3 to 80 but it took several days of waiting and shaking once in awhile. I assume it can go higher but I haven't got that far yet.

 

[jonny nugs]

cool i learned something thanks.

 

[VIKINGtrich]

Really cool thread, lets not lose it in the pile of deads threads.....So a BUMPITY BUMP is in order, I do believe...

I always use Dolo Lime, I wouldn't want to grow in peat without it, it makes me sleep easier at night... Since i started using Dolo lime, I started growing killer, Grade AAA ganja....Shit works good to buffer ph......I still use a PH pen, and water/feed everything at 6.5 or so, EVERYTIME! Might not have to be so anal about my PH, but again, It helps me sleep at night.

Later Lime-Heads.

By the way, Verdant Green, "May the PHorce be with you"------I DIG IT!

 

[tr1ck_]

Just want to add my experience here - dolomite lime is great but it's EASY to over-lime your soil, I have lost SEVERAL plantings this way. The lime WILL retard growth and/or kill your plants if there's too much in the soil.

The 2 tablespoon/gallon dose is great for soil you make from scratch with a lot of peat and/or nutes in it.

I am using MG organic choice with 40% perlite as well as 1.5 tbs/gallon of Dolomite Lime. I just recently read that this soil is high in PH already, will I be able to keep this in check if I water with very low ph water?

 

[Azeotrope]

I was just thinking..... I haven't added any dolo lime or lime of any sort for a looong time. NO PH issues either.... Maybe it is that I use very well aged compost that has lots of broken down small egg shell pieces, a fair amount of small willow branch chards and everything else you can imagine. Grass clips, yogurt, tons of veggie and fruit matter, azomite, kelp meal, leaves, humic shale ore etc...

The other things I add in large amounts are worm castings, coco fibre, hard wood charcoal/ashes and lots of diamotaceous earth (fine food grade). Do you guys and gals think that the DE helps to buffer the PH?

Edit - I add 20lbs of used carbon anually and I always empty my mix back in to the compost post harvest.... I wonder if the carbon helps buffer PH? Guess I always thought PH wa a non issue with Organics.

 

[B. Friendly]

my garden centre put out a flyer saying this about Dolemite Lime;
NEUTRALIZES SOIL ACIDITY
Supplies calcium and magnesium
speeds the decay of organic matter, a must for organic growers
increases the fixation of nitrogen by soil and plant organisms
improves yeilds
improves the physical properties of soils
reduces the activity of toxic substances in soil.

it's good stuff

puff on

 

[Azeotrope]

B. Friendly - You are correct. It is great stuff. I just ran out a long time ago and never seemed to give it any thought.

 

[DiscoBiscuit]

Check this out if you're curious of dolomitic rate/ fert rate
http://mrec.ifas.ufl.edu/Foliage/Resrpts/rh_95_4.htm

 

[OPT]

I will also stress to make sure you read the label. I actually bought some so called "dolomite lime" a few years back, used it a few runs and kept getting the same issues with the leaves that looked like a cal/mag problem but never could fix it. I never PHed my water because I was always read and told that dolomite lime will help buffer your PH.

After changing to coco, I was looking back at the lime bag one day out of the blue, and I noticed the word "Hydrated" on the back. Hydrated Lime is not the same as dolomite, so I suspect this was the cause of my problems all along.

One of the main reasons I changed from organics to coco was because I couldn't figure out what I was doing wrong. Now that I know what I do, I plan to give it another try in the organic world!

The dolomite lime I will be using with my mix will be Sunleaves Soil Sweetner.

OPT

 

[STRAINZ]

Very informative thread...k+!

I'm interested to hear any comments on this fairly new CaMg product from Gen Organics. It is catalyzed from oyster shell & dolomite lime. Here's some info:

CaMg+ is a plant supplement that provides a natural source of calcium and magnesium, elements that are critical during your plants' growth cycle.

These essential elements help your plants build strong healthy cell walls and promote disease resistance. They also optimize plant metabolism, enhancing growth and creating healthier flowers and fruits.

Calcium and magnesium are often absent in many fertilizers and potting mixes, which can result in stunted plant growth. Adding CaMg+ to your existing fertilizer program increases calcium and magnesium transport into the plants.

CaMg+ is biologically catalyzed from oyster shell, dolomite lime, and natural plant extracts (not calcium nitrate).

Application rate: use 5 mL per gallon

General Organics, an organic nutrient line from General Hydroponics, are 100% natural.

 

[LeenieBean]

great thread. As you can see by my current grow in my sig- Sensi Star now 49 days in, no dolomite lime spelled disaster for me! S I just ran out of powdered dolomite lime and will be using pelleted. very informative!

 

[Stromisle]

What about Liquid Lime? just as good as powdered form?

 

[gully laganj]

I just noticed my pro-mix hp has dolomitic and calcitic lime added to buffer the ph. I've been pulverizing the same type of pelletized DL lime in a coffee grinder because it is all I have currently. Will source something else and use the other stuff outside. haven't had problems but I strive to achieve best practices

Can I substitute fossil shell flower as a cal mag source for DL, esp. if I shift to a more coco base mix instead of peat? will this fresh water DE fossil shell flour also help with pest management?

my base mixes are a combination of manna mix coco (4pts), promix hp (2pts), and organic mechanics premium potting mix (2pts)

To that I add perlite, rice hulls and ewc .

Into my dry amendment mix, which is about 1/3 strength as recommended in LC's mix in sticky thread. This is made up of bone, blood, kelp meals, rock dust, guano, and about 1/3 the recommended amount of powdered DL. (less than TBS per gal)

I top dress feed ala C.C.'s thread , with plain water... but supplement waterings with molasses which is 10% cal and 8% mag. No deficiencies thus far

I have biochar, fossil shell powder and neem cake I'd like to add to soil mix but am still trying to figure out how and why they would benefit me.

I sometimes use bioag ful power, mostly in first wettings of media and as a foliar with various accompaniments at different stages

ICmag is the shit, this place by far has the least amount of mis info and gullible growers

 

[gully laganj]

ha just noticed how old this thread is! Maybe this getting re upped will give someone else incredibly useful info as it did me! Yeeee HAAAAWWWWWW

 

[BOMBAYCAT]

I'm an organic grower with a Ph pen because the water here sucks. Also I couldn't find Dolomite around so I use Agricultural Limestone which they claim is the same thing.

 

[BurnOne]

You can get powdered dolomite lime on Ebay.
Burn1