Soil pH and plant health

Page last updated: Monday, 16 June 2014 - 2:10pm

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Changing soil pH

Soil pH is generally corrected using iron sulphate (decrease) or lime (increase). There are some organic soil improvers on the market which are claimed to stabilise the pH on neutral. Make sure the soil additive is well worked and watered into the soil.

Leaf showing yellowing and spotting.
Manganese deficiency on a cycad leaf.

Acid soils

To increase the pH by one point, apply dolomite lime at 100g/m2 in sandy soils, and up to 250g/m2 in clay. The effect is noticeable after two to three months.

Alkaline soils

To decrease the pH, iron sulphate is available from nurseries and hardware stores. Follow label instructions for the correct rate. Compared to lime, the effect is immediate.

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