# Can limestone rock affect soil pH or soil conditions?



## Sapling

I was wondering about this decorative limestone landscape rock that a lot of people have incorporated into their landscaping, gardens, etc. I have been speaking with a gentleman who is having problems with his Spruce trees. First of all he has a very high water table which seems to be causing problems with too much water but in addition he has covered the ground under the trees with a thin layer of this rock. Could this be adding to his Spruce problems?

What exactly is the make up of the rock? Is it just called Limestone rock because of its colour or is it really limestone and does it have all of the properties of limestone? I have no clue, obviously! Any info you could give me would be great. Thanks in advance.


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## chainsawaddict

Sapling said:


> I was wondering about this decorative limestone landscape rock that a lot of people have incorporated into their landscaping, gardens, etc. I have been speaking with a gentleman who is having problems with his Spruce trees. First of all he has a very high water table which seems to be causing problems with too much water but in addition he has covered the ground under the trees with a thin layer of this rock. Could this be adding to his Spruce problems?
> 
> What exactly is the make up of the rock? Is it just called Limestone rock because of its colour or is it really limestone and does it have all of the properties of limestone? I have no clue, obviously! Any info you could give me would be great. Thanks in advance.



Limestone is generally Calcium Carbonate (CaCO3) cemented rock(sandstone), and is very soluble.

I dont know about about the rock you are using, but a good test is to drop diluted hydrochloric acid on the rock, if it bubbles, it is Calcium Carbonate. I am a geologist, not a chemist, so I am not sure exactly how much the pH is changing, but I would assume it would slightly. As far as enough to kill spruces, I doubt it. Ive seen spruce trees growing out of limestone formations in the black hills of south dakota.


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## ATS/TexasTree

Spruce trees generally do best with soil pH ranges from 5.5 to 7.0. 

Limestone can drive the pH up, especially if the water is a little alkaline. 

Spruce needles would be a better mulch beneath the tree rather than limestone.


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## chainsawaddict

ATS/TexasTree said:


> Spruce trees generally do best with soil pH ranges from 5.5 to 7.0.
> 
> Limestone can drive the pH up, especially if the water is a little alkaline.
> 
> Spruce needles would be a better mulch beneath the tree rather than limestone.



good point, it would depend on where the soil pH is starting in the first place.


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## ATH

chainsawaddict said:


> good point, it would depend on where the soil pH is starting in the first place.


And how well buffered it is.

I would have to think that the limestone rock is having _some_ impact to raise pH...but I doubt it is more than a couple of tenths over several years/decades.

If you want somewhat of a better idea, look at how much powder you get out of a bag of the rocks. Then look ar recommended liming (in pounds per thousand sq ft) rates to raise the soil pH for turf. How big of an area are you covering with the rock (number of bags?), and how much of the rock is lost to break down each year?

I don't know for sure...just thinking out loud here. Please post back if you find any actual studies!


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## Sapling

I found a few websites which talk a little about this topic. If you are interested....
http://www.ext.vt.edu/pubs/envirohort/426-724/426-724.html


This one mentions the yellowing of evergreens which is interesting because at least one of the trees on this site is yellowing and we were not too sure why.http://www.solutions.uiuc.edu/content.cfm?series=4&item=480


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