# Calcitic vs Dolomitic Lime...length of effectiveness?



## Iharfstra (Sep 28, 2018)

Hey All...first time poster here. I'm starting my second fall at my current home. I'm in maryland, with loamy soil. Yard is mostly Tall Fescue, with some Fine Fescue in a shady portion. I just sent off a soil sample to Soil Savvy...but I expect that my pH will be low. Assuming that's the case, I know I'll need to drop some lime...and quite frankly, the Calcitic vs Dolomite Lime discussion perplexes me. I see so much contradictory information regarding their relative benefits.

First and foremost: Does Calcitic last just as long as Dolomitic? I've seen info saying that Calcitic only lasts a few months while Dolomitic lasts a few years (but is very slow to take effect). I've also seen info saying that they last the exact same amount of time and that the only benefit to using Dolomitic is the magnesium included in it.

What's the truth? Does one last longer (for pH purposes) than the other?


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## adgattoni (Oct 3, 2017)

There's a bunch of great info on Lime in Ridgerunner's Soil Test Thread. I would assume if it isn't there, it probably isn't anything to worry about. @Ridgerunner has been pretty thorough there.


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## Ridgerunner (May 16, 2017)

> What's the truth? Does one last longer (*for pH purposes*) than the other?


No.


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## Green (Dec 24, 2017)

I believe what you're thinking of is fast acting vs. Agrucultural lime. I'm sure there is someone here who can explain the difference well. I've only used fast acting so far, because I needed quick (5 year) corrections.


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## Iharfstra (Sep 28, 2018)

Thanks for the responses, all...much appreciated.


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## alpine0000 (Jul 25, 2017)

Dolomitic Lime:
-Calcium + Magnesium (65% calcium)
-Moves very slow (can take years to move a few inches in the soil)
-Apply 92 lbs per 1000 sq ft to raise the pH 1 full point

Calcitic Lime:
-Calcium + Calcium Carbonate (80-90% calcium)
-Moves very fast (results within weeks), but doesn't last long (few months)
-Apply 23 lbs per 1000 sq ft to raise the pH 1 full point


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## Ridgerunner (May 16, 2017)

Are you really sure about that @alpine0000 ?


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## Green (Dec 24, 2017)

Ridgerunner said:


> Are you really sure about that @alpine0000 ?


Doesn't the exact formula vary by location?


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## Ridgerunner (May 16, 2017)

There are a number of variables/factors involved.
At the risk of being repetitive:
Low pH is due to the amount of hydrogen in the soil. The more hydrogen, the lower the pH. When hydrogen is removed from the soil, pH will raise. 
The most common agent/active ingredient used to remove/neutralize hydrogen is carbonate.
The two most common sources for carbonate for soil application are calcitic lime and dolomitic lime. Pound for pound, dolomitic lime contains more carbonate than calcitic lime. However, because the way the dolomitic lime molecule is formed, dolomitic lime is slower to react with with hydrogen, so it can take about three months longer for dolomitic lime carbonate to remove the same amount of soil hydrogen as it would an equal amount of carbonate from calcitic lime. 
As lime (dolomitic and/or calcitic) is a mined resource, it's quality/purity varies. Calcitic lime (most products contain 30-35%Ca by bag weight) cannot contain more than 6% Mg and still be labeled calcitic lime. Greater than 6% and it is classified as dolomitic (commonly, dolomitic limes will be about 11% Mg and 21% Ca by bag weight).
The finer the lime is ground, the faster it will dissolve and react with the hydrogen. Compare the difference in how fast an ounce of rock candy will dissolve in hot tea vs and ounce of rock candy that has been pulverized into dust.
A low CEC soil with a pH of 5 will need less carbonate (lime) to raise pH to 6.5 than a high CEC (more hydrogen is present in reserve) soil with a pH of 5 will need to reach a pH of 6.5.
As carbonate/lime will leach quicker through a sany soil than a clay soil, the depth of the pH change will be greater in a sandy soil.
Those are some of the variables involved.


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## adgattoni (Oct 3, 2017)

Ridgerunner said:


> There are a number of variables/factors involved.
> At the risk of being repetitive:
> Low pH is due to the amount of hydrogen in the soil. The more hydrogen, the lower the pH. When hydrogen is removed from the soil, pH will raise.
> The most common agent/active ingredient used to remove/neutralize hydrogen is carbonate.
> ...


Another question that seems to get asked a lot is: does one lime product _last longer_ than another? Based on your explanations above and elsewhere on the forum, I haven't seen that addressed. Does this hydrogen somehow "come back" over time, or permeate up from deeper soil? Or is this notion of the products "expiring" after a period of time just created to sell more products?


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## Ridgerunner (May 16, 2017)

> Does this hydrogen somehow "come back" over time, or permeate up from deeper soil?


Hydrogen is constantly being added to the soil via a number of sources. Rain, the decay or organic matter, ammonium and urea fertilizers, and yes from the upward wicking of water from a lower soil level if that solution is acidic. Therefor, low pH soils that have been corrected eventually become more acidic again over time. (So why don't we see high pH soils getting more acidic? Because of the vast amounts of lime, carbonates and bicarbonates, in them are so great that the added hydrogen doesn't make a dent in the pH plus the water solution that wicks up will be high in pH. This (lowering pH) has been discussed elsewhere on the forum.)


> Or is this notion of the products "expiring" after a period of time just created to sell more products?


"Depleted" would be a more accurate term. Once all of the carbonate in the product has interacted with the hydrogen, no more neutralizing affect can occur. The carbonate has been used up.


> does one lime product last longer than another?


As dolomitic lime is slower to interact with hydrogen, I suppose you could classify it as slower release carbonate. Technically if you could predict how long it would take for dolomiic to react (estimates are 3-6 months longer than calcitic) and if you could predict how much hydrogen will be added to the soil over that period of time, the total amount of dolomitic (i.e. the amount of carbonate to reach the desired pH plus the additional amount needed to counteract the continuous hydrogen build up) you could maintain a constant pH level for a longer period of time - "last longer." But, there are too many variables to calculate that anywhere near accurately.
That make sense?


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## alpine0000 (Jul 25, 2017)

Ridgerunner said:


> Are you really sure about that @alpine0000 ?


Yes. Those claims came from grass factor's videos. And align with a lot of research I've done.


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## adgattoni (Oct 3, 2017)

@Ridgerunner - good stuff sir. Appreciate it!


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## Ridgerunner (May 16, 2017)

There are a number of decent articles out there, but this is one of the better ones that explains the science/chemistry and the multiple factors involved regarding lime use. FYI:
http://www2.ca.uky.edu/agcomm/pubs/id/id163/id163.pdf


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