top dressing with limestone aggregates.
cedarglauca
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in Talkback
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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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.
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 !
Did you teach chemistry Steve?
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.
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.