Liming

Calcium is required as a plant nutrient, but its main effect is on the soil pH or acidity. This can dramatically affect plant growth, mainly by its influence on the availability of other nutrients.

Calcium, Potassium, and Magnesium all become less available to plants as acidity increases (pH gets lower), whereas Phosphorus (which requires a slightly acid soil) is unavailable to plants in relatively acid and high pH (alkaline) soils.

For vegetable production aim for a general pH of around 6.5 - 6.8 (5.8 - 6.0 for peat soils). Never apply lime so that pH goes above 7.0.

If a soil analysis indicates that lime is needed then apply a suitable liming material such as ground limestone or ground magnesian limestone (dolomite) at the appropriate rate shown in the following table.

Approximate amounts of lime required to raise pH to 6.5
(5.8 for peat soils)
in kg of ground limestone per sq metre
original soil pH

sandy soil

loam soil

clay soil

peat soil
6.0

0.25

0.4

0.5

0
5.5

0.5

0.8

1.0

0.6
5.0

0.7

1.2

1.5

1.2
4.5

1.0

1.6

2.0

1.9
Note:
Do not apply more than 0.7 kg of lime/sq metre at any one time.
Use repeated applications at intervals of several months.
See also Vegetable pH preferences for pH preferences of a range of vegetables

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