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The Virtues of Dolomite Lime

the gnome

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if your having cal-mag deficiencies can you just add some powdered dolimite to water and then do your plants
up with that?
 

grapeman

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if your having cal-mag deficiencies can you just add some powdered dolimite to water and then do your plants
up with that?

sure, but I'd also do something a bit quicker acting. Like spraying epsom salts for mg or cal-mag if you are not organic.
 

Albertine

Member
How great this thread showed up! I am trying to figure out all this as I've been repairing crashes by repotting and I can't go any bigger, so I have to get it right now. The cycle has been - everything looks great in new soil, then a few waterings in they start yellowing and showing what I think are typical mag deficiency symptoms, pale with mottled chlorosis, with a runoff ph in the 5s. Sunshine #4 is what I am using- and after adding 2T/gal extra dolomite plus some ewc I am still at 5.0-5.5 ph in the mix. I am mixing and using immediately, and everybody looks really good - regreening of yellowed leaves, within a week or so of repotting.

Water alkalinity is a problem with me - out of the tap I'm at 25ppm. I've started adding cal-mag to 200ppm before adding a nutrient tea which is also at about a 5.0 in order to give it some buffering capacity. I'm using protekt silica for a phup to take it to 7.0, and watering with that I'm getting a runoff ph of 6.0, finally.
I added some dolomite to the last batch of tea, 1 tsp/gal - and I am wondering the same thing as the Gnome - why can't you water the dolomite in? It seems like it could be a really good organic substitute for cal-mag and give more buffering without adding all those salts.
 

SupraSPL

Member
Good discussion going here. I have been wondering about all this too.

Thanks OP for bringing attention to pulverized lime. I am using pelletized and crushing some of it up manually to get a mixture of particle sizes. Now I will have to go check out my label and if it is lesser than the pulverized I am heading for Ace Hardware.

Thanks Verdant for pointing out that lime can act quickly for PH. I did a similar experiment and the lime raised the PH to 7 and settled there (within hours). I have also noticed that it only takes a week or two for the lime to stabilize the PH of (damp) peat and the process does go quicker if there are smaller particle sizes included. The larger particles add the longevity for a long growing cycle.

Another interesting point was mentioned about dolomite releasing cal and mag as it neutralizes acids from ferts and peat. I'm thinking for R/O users this could solve calmag problems when used in combination with blackstrap molasses?

Verdant you said you have a PH pen, do you happen to have access to R/O and an EC meter? It would be interesting to see if the EC or PPM rises as the dolomite neutralizes the carbonic acid in R/O (or citric if added). If so, would that rise in PPM represent the cal and mag that would be available to the plant ?
 

Ulysses

Member
Thank you Vonforne for re-opening my sticky.

Recently, another spate of questions has arose on this forum regarding lime. My original intent was to keep this sticky simple and easy- no math, no physics, little if any chemistry...

A few more tips from the questions I've been asked-

Buffer- means to keep the pH in a desirable range. This happens slowly. You don't want your plants experiencing wide/wild flucuations in pH. This may be one possible cause of hermies, IMHO. Pulverized Dolomite Lime will not only buffer pH but will also add the necessary Cal/Mag in the proper proportions- thus killing two birds with one limestone!!! Did I mention it's cheap?

Cal/Mag Solution, the kind you get at the hydrostore, contains a fairly high dose of Nitrogen (2-0-0) if I remember correctly. You can easily fry your plant with the N. Use it sparingly if at all, and work up to the recommended dose. This is an advanced user indoor nute and does not buffer pH...

Sprouts or Seedlings- don't get cal/mag deficiency. What they do get is Overwatered. Often.

Epsom Salts- AGAIN, I'll admit that mj loves magnesium. Trying to calculate how much magnesium your plant is actually going to get in a dose of salts or how much to mix in a gallon of water to correct a plant deficiency is advanced organic chemistry or physical chem calculations... Been there done that got the sheepskin. This is strictly for the advanced class because it's too easy to kill your plants with an overdose of this stuff. Instead, source some Pulverized Dolomite Lime and be confident that you won't develop a magnesium deficiency...

Coco Coir- lime is added to peat moss based media with organic matter as fertilizer because these create acidic conditions as they breakdown. Coco coir doesn't turn acidic as I understand it. I got a considerable amount of coco from a grow I consulted on and this was rinsed and added to my 'soil' mix two years ago. As my soil remains mostly peat and earthworm castings, I continue to amend with Pulverized Dolomite Lime and enjoy the benefits- my Blueberry buds have never been better. If you are starting a fresh batch of soil, I recommend calculating the amount of lime based on the amount of organic matter in the mix leaving out the perlite and the coco coir. I am by no means a coco expert- still learning the stuff but I've noticed a marked improvement in the end results...

Gypsum+Hydrated+SulPoMag- Wow! You'd have to be a soil engineer to get this correct! You'd have to source THREE different bags of material! You'd probably have to measure by weight of each amendment and run a spreadsheet! Too much BS. Get a bag of Pulverized Dolomite Lime. Please...

Tomatoes and Lawn- Hell Yes. My old man, may he rest in peace in the great garden in the sky, added Pulverized Dolomite Lime to his tomato garden every year I can remember. Years later, he told me that's what the Italian guy at work instructed him to do. He never questioned the advice. He always presented my mother with succulent tasty tomatoes which she continues to love to this day- now she get them from me ;) Guess what? He never even owned a pH pen...
 

VerdantGreen

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...
Verdant you said you have a PH pen, do you happen to have access to R/O and an EC meter? It would be interesting to see if the EC or PPM rises as the dolomite neutralizes the carbonic acid in R/O (or citric if added). If so, would that rise in PPM represent the cal and mag that would be available to the plant ?

hey supra i dont have an ec meter or R/O but i was thinking along similar lines myself. i posted in another thread about using a mineral water that was high in cal/mag to correct deficiency and ive been thinking that a cal/mag 'tonic' could possibly made by making some water acidic and then neutralising it with dolomite lime. i would imagine the dolomite that dissolves would then be available to the plant. perhaps someone who knows better than me would confirm that?

VG
 

SupraSPL

Member
I've been experimenting with spring water and mineral water. First thing I learned is that the mineral water has too much sodium. Sweet spring water however is fine and has a nice balance of cal mag but most of its ppm comes from carbonate and I'm not sure what the consequences of that would be when recycling soil.

I dumped some dolomite into a jug of R/O shook it up and let it sit for about 24 hours. The PH rose from ~5.8 to ~7.1. Unfortunately I do not have a PPM meter but I have been giving this water to plants that I suspect are in cal mag deficient recycled soil and on the lookout for improvement.

If this works I will just keep a pile of dolomite in the bottom of the water jug. Since there is dolomite lime already in the soil and cal mag in the molasses I hope I can avoid using calmag plus in the recycled soil.

If it does not work maybe I will try the citric acid and see if that can free up more of the calmag.
 

Ulysses

Member
Thanks for the question... I'm going to answer in the thread for the benefit of all...

Yes, I am aware that Tom Hill uses gypsum his soil mix and grow op. Tom Hill and associates have my greatest respect and I often fantasize about my plants reaching those proportions!

That being said, Tom has a very comprehesive control over his environment, and let's face it, he's got it tuned in... He states his water source is pH 8 so that is a factor. He also states IIRC, that he would add pulverized dolomite lime for half the gypsum 50/50 if his water was not just so...

This has me wondering if magnesium is really that big of a deal??? Some speculate that magnesium makes the herb harsh to smoke? Where do Tom Hills plants source their magnesium? Hmmm.

Second question- pH paper strips are very inaccurate. I feel they are only best for detecting extremes in pH fluctuations. For example, the difference in color for a pH 6 and 6.5 is going to be difficult to discern - I've used paper strips in the past- I still have some. So yes, I am a propeller head, and no, I don't run around with a pH meter pH-ing everything in sight...

Nowdays, I simply add 2 tablespoons of pulverized dolomite lime per gallon of mix and don't worry about pH again. It's a two for one winner- pH buffer and cal/mag! I need to keep it simple... Thou' I will often give a dose or two of molasses (organic Cal/Mag plus iron and carbs) to boost flowering!

Best of Luck
 

the gnome

Active member
Veteran
I have a bag of lime, its 32% CA and 4% Mg
it doesn't have the Mag percentages of dolo but it does have it.
any disadvantages to using it?
 
C

Carl Carlson

http://www.greenhousegrower.com/magazine/?storyid=185

Understanding Plant Nutrition: Limestone and pH

By Bill Argo and Paul Fisher and Jinsheng Huang
March 2008

2librqg.jpg

There are three Rs of limestone incorporation —requirement, reactivity and residual. The lime requirement is the amount of acidity contained in a given volume of media or media component that has to be neutralized to raise the pH to some desired level, usually around 6.0.

[..]

Limestone reactivity describes both the amount of pH increase that can be expected from a given incorporation rate and the time needed for the media pH to stabilize (usually 7 to 14 days after mixing at greenhouse temperatures and adequate moisture condition). For carbonate-based limestones, the reactivity is affected by a number of factors including the chemistry of the limestone [calcitic lime (CaCO3) versus dolomitic lime (CaMg(CO3)2)], acid neutralizing value (purity), surface area (hardness) and the particle size distribution.

Research at the University of New Hampshire and the University of Florida demonstrated that the particle size distribution best described the reactivity of a limestone. The limestone particle size that is responsible for causing the media pH to increase initially is that fraction which is finer than 150 µm (will pass a 100 mesh screen).

In general, anything finer than 75 µm (will pass a 200 mesh screen) will react completely and rapidly, reaching the equilibrium pH within a few days to a week. A lime particle between 75 and 150 µm (100 to 200 mesh) will still react almost completely, but rate of the reaction will be slower. The particle size distribution for 29 limes used in commercial production and analytical grade CaCO3 is presented in Figure 1.

On any bag of lime, the particle size distribution for that limestone should be specified. For example, a pulverized limestone will have minimum of 65 percent passing a 150 µm (100 mesh) screen, a superfine limestone will have minimum of 65 percent passing a 75 µm (200 mesh) screen, while a microfine limestone will have minimum of 95 percent passing a 45 µm (325 mesh) screen.

However, with the exception of the microfine limestones, these definitions can be misleading. For example, the lime designated as D11 in Figure 1 is sold as a pulverized dolomitic lime. With this lime, 79 percent of the material passes a 150 µm (100 mesh) screen, while 58 percent of the material passes a 75 µm (200 mesh) screen, making the D11 lime finer and more reactive than its designation suggests.

Not all the limestone incorporated into a root medium initially reacts to bring the pH up. The limestone that remains unreacted in the media after the equilibrium pH is reached is termed residual lime. It is the residual lime that can give significant pH buffering to container media.

Figure 2 shows the results from an experiment at Michigan State University, in which the same peat/perlite media was prepared using two different types of lime. The low-residual treatment contained a hydrated lime, that reacted quickly and completely leaving no residual. With this treatment, the only buffering comes from the CEC of the peat. The high-residual lime treatment contained a dolomitic lime with a large residual fraction. Impatiens were grown with an acidic fertilizer solution for 17 weeks in both media.

The medium-pH changed much more in the medium containing hydrated lime, because there was no residual lime in that medium to buffer the pH over time. In this experiment, it is important to note that the peat, the plant species and the volume of acidic fertilizer solution were similar for both treatments. The only difference was in the lime used.

The particle size that affects residual lime is between 850 and 150 µm (20 to 100 mesh) (Figure 1). When these coarse particles are incorporated into a medium, some of the lime reacts to help increase the media pH, but some also remains as residual lime for buffering. With the 850 to 250µm (20 to 60 mesh) fraction, about 65 percent of the lime reacts and 35 percent will remain as residual lime. That means if 10 pounds of this lime fraction were incorporated into a container medium, 6.5 pounds would react to bring the pH up, while the remaining 3.5 pounds would remain as residual lime. cont.​
 

Muleskinner

Active member
Veteran
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.

However, most commercial soil mixes already have lime (or something similar like shells to balance PH). If you add 2 TBLSP/gallon to these your plants will die. I have DIRECT experience with FFOF, Hoffman, and Coast of Maine soil mixes in this regard. They are all pre-limed (or shells, etc).

I do believe lime can be added to these mixes but at a much lower dose. You do need to add some lime if you intend to use heavy EJ ferts. But for most pre-mixed soils, if there's any lime in there you need to use much less than 2 TBSP/gallon.

If you've added lime and are getting yellow leaves, slow growth, or dying plants then it's quite possible that too much lime is the cause. If you're in doubt about whether the soil products you bought are pre-limed or pre-balanced then call or email the manufacturer and find out before adding your own.

The dolomite lime from Sunleaves says 2 TBLSP per 5 gallons soil, that's .4 TBLSP per gallon. So the appropriate range is probably between .4 and 2 TBLSP per gallon depending now how much you need to balance your mix and how hot your nutes are.
 
Ive been making my own compost for several years now, poo & peat mostly.

Have used well water, wild spring water, RO & use Earth Juice.

One would think my mix would be rather acidic & need a good shot of lime.

BUT every time I add lime - even rates as low as 1/2 TBS per Gal my runoff is in the low 7's & the plants growth is poor.

If I leave out the lime & just use molasses & gypsum to combat cal / mag deficiencies things work ALOT better for me.
 

SupraSPL

Member
A few years ago I ended up with a 40 lb bag of pelletized dolomite lime. Apparently it is made from chunks of lime that are coated in some sort of clay or binder. When I rinse the coating off and measured it the ppm and pH are both through the roof. After I rinse the coating off the white lime left behind behaves normally and affects the PH like you would expect ~6.5pH in peat.

So when I am mixing up a new batch of soil from scratch the pH can get too high due to that coating and it takes some time to leach it out of the soil. It definitely retards growth I almost lost a few seedlings and clones before I caught on. From now on I will look for pulverized lime or I will take the time to rinse that coating off the pelletized lime before mixing into the soil.
 

Albertine

Member
For some reason finding unpelletized lime has been difficult for me - tried to special order the sunleaves and it never came in for whatever reason.
This summer I found some dolomite at Home Depot that was a Lily Miller product, Soil Sweet, with a varying mesh size to it - 11% will go through a 100 mesh.
 

Clackamas Coot

Active member
Veteran
Albertine

There are 2 forms of 'pelletized' minerals. Unfortunately to the layperson they both look alike and work the same way.

First there is 'prilled' limestone (or whatever the agent) which is coated in a clay (a good thing) and in the prilled form the clay is released quickly when it comes into contact with water. Clay is water soluble but it can be dispersed by water/moisture. In this form the limestone (or whatever the agent redux) is as available as the unprilled version for the sake of this discussion.

Next up is 'pelletized' limestone (or whatever the agent redux redux) which is also coated with clay and it's either a heavier application of the clay or a different clay is used. This results in a limestone product (or whatever the agent redux redux redux) that breaks down slowly.

Because of the worker safety laws regarding dusts and whatever, the prilled and pelletized versions of many soil amendments are becoming the most common versions - especially at the retail level.

If they're selling a dolomite lime or straight limestone product at Loews or HomeDepot you can almost go to the banks that it's the prilled and not the pelletized meaning that you're good to go. Pelletized is the version that you'd likely find at a farm/feed store in more rural areas because it's the one most used in agriculture vs. the home gardener.

HTH

CC

P.S. - get limestone or oyster shell powder over dolomite lime. Just my opinion of course, i.e. I don't worship at the altar of the dolomite lime Gods.
 

Albertine

Member
Actually, I had been seeing the pelletized or prilled type and not buying it, but this is just like ground rock - no balls, just not very well ground up rock. Picked it up this summer. Tried mixing it with some pelletized I got by mistake, but no comments on how it worked. I do believe I am getting more time in my veg pots before showing mag defs, but I am also on a no runoff kick so who knows. That Solomon recipe you are using sounds like a good direction to move toward as I really like the idea of diversifying ingredients.
I had been using what I had in my stash of pottery glaze materials before that. It is dolomite at around 150 to 200 mesh, but never got a breakdown as to cal/mag ratios. That could have been helping me get more mag defs faster as it could wash out so quickly at that mesh size.
 

spurr

Active member
Veteran
Here is worthwhile info if it has not yet been posted in this thread:

Carl Carlson wrote:
https://www.icmag.com/ic/showpost.php?p=3908513&postcount=10

Ok check it out, I sent an e-mail to Bill Argo asking about this subject.

Well known researcher Bill Agro wrote:

Yes, it is possible to add too much lime.

However, the maximum upper pH range for container grown crops is somewhere around 7.8 to 8.5 as long as there is soluble calcium in the system. At this pH range, calcium carbonate will begin to precipitate, and acts as a buffer that resists media pH the going above that range. In theory, the reason that it is not an exact pH is that it not only depends on the concentration of calcium in the system, but also the partial pressure of CO2 in the soil environment. If the CO2 partial pressure is high, then the maximum pH is lower (around 7.8), while if the CO2 partial pressure in the media is closer to atmospheric CO2, then the maximum pH is closer to 8.5.

Based on several experiments, the maximum pH in plants grown in peat-based media is around 8.5.
 

MrFista

Active member
Veteran
i posted in another thread about using a mineral water that was high in cal/mag to correct deficiency and ive been thinking that a cal/mag 'tonic' could possibly made by making some water acidic and then neutralising it with dolomite lime.

VG

I can help you with a buffer solution using dolomite and citric acid if you like.

I'll need the actual molecules structures/formula to see what it is I'm working with.

Bit flat out but can look at this tomorrow, or next weekend.
 

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