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Alkaline Soil - how much acidifier do I need?

I have very alkaline soil (It is a terrace hous with 100 years of tenants adding fire ash to the garden, and several renovations when lime-mortar from the bricks would have been spilt on the soil - these have made it very alkaline.

I have tested the Ph and it is 8 to 8.5!

The garden is 4 metres by 10m = 40 square metres

1: What product should I use?
2: how much should I add?
3: who can supply this in big bags (near Newtown, NSW)
3: If I add too much, will this make toe soil too acid?


Submitted: 02:13PM, 13 Dec 2009
Answer: Dear Lidiya,
Soils with a pH of over 8.4 usually contain several per cent limestone. All of this limestone has to be dissolved by acid before the pH of the remaining soil will start to drop. It is expensive and not easy to do. It is usually rather fruitless to try to lower the pH of such soils.

If the pH is around 8, applying sulphur will lower the pH and it is the cheapest material to use to drop the pH. Sulphur can be purchased from your local garden centre or any of the large retail produce store.

You might find that the pH is higher in some areas than others, and not the entire 40 sq.m has a pH of 8 to 8.5. Also it might be a good idea to see whether just the top 15cm of soil has such a high pH reading. By removing that layer and testing the soil below, you may find that the soil has a lower pH and something you can work with. You can then import some garden soil which will enable you to grow the plants of your choice.

Answered: 01:28PM, 16 Dec 2009


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