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top dressing with limestone aggregates.

Hello...I have an area which contains a number of established shrubs and trees,some of which are lime intolerant : If I top dress with a decorative Cotswold stone (limestone) aggregate, is the action of rain over time likely to raise the alkalinity of the subsoil to a detrimental degree?  Thanks all....Tom.

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  • DovefromaboveDovefromabove Central Norfolk UKPosts: 79,336

    I wouldn't take the risk - I don't know but I imagine that it's highly likely - I'd use pea gravel or slate chippings instead. 

    image

    “I am not lost, for I know where I am. But however, where I am may be lost.” Winnie the Pooh







  • Steve 309Steve 309 Posts: 2,753

    Definitely.  The carbonic acid in the rain (natural or man-made) will react with the limestone (calcium carbonate) and calcium bicarbonate will leach into the soil below.  This will react with the soil acids, raising the pH.

    Limestone streams in the White Peak. Derbyshire caves.  Sink holes and all that.  Ground limestone is one form of lime we use to raise pH!

    Slate and granite are slightly acidic, if there's any significant breakdown at all; slate waste is probably  more eco-friendly, if it is indeed waste from quarries.

  • Thanks a lot Steve and Dove....sound advice,which I shall act on ! 

  • DovefromaboveDovefromabove Central Norfolk UKPosts: 79,336

    Did you teach chemistry Steve? image

    “I am not lost, for I know where I am. But however, where I am may be lost.” Winnie the Pooh







  • Steve 309Steve 309 Posts: 2,753

    Only incidentally.  Biology mainly, and we used to do field courses at Malham, so I know about limestone.  And my best friend's a Geography teacher.  Amongst other things.

  • lisa masseylisa massey Posts: 252

    When rainwater runs over limestone the water picks up traces of lime making it alkaline. Limestone should never be placed above sandstone in a building because of the detrimental effect the alkali water has on the acid based silica(bonding structure of sandstone). I would say that it would have a similar effect on ericaceous plants.

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