Soils Acidity and Liming

Why do soils become acid

Calcium leaches with excess rainfall Acid rain increases this As does application of ammonium

nitrate, urea and ammonium sulphate Crops remove calcium Soils naturally rich in lime will not

become acid

Target pH: Mineral Soils

Arable 6.5 Mixed rotation - barley 6.2 Mixed rotation - wheat 6.0 Grass or grass clover 6.0

If SBT grown 6.5 to 7.0

Sampling for pH

To sample a field walk the W, taking at least 20 subsamples (0-20 cm for arable, 0-15cm for grass)

Test using approved method, Garden test kits questionable.

If you have patches of poor growth sample separately. Acid patches common on light soils.

How much lime to apply

Depends on:

Soil Texture Initial pH Target pH Liming material

Table in RB 209 gives amounts

Liming Materials

Material NV Ground chalk or limestone 50–55 Magnesian limestone 50–55, over

15.3% MgO Hydrated lime c.70 Burnt lime c.80 SBT Factory Lime 26-27

Management Considerations

Split large dressings(10t/ha +), plough ½ down and work rest into surface.

Never apply more than 7.5 t/ha to established grass.

Lime will increase common scab on potatoes, potatoes are acid tolerant. Don’t lime before potatoes.

SBT and Barley are sensitive to acid soils, lime ahead of them.

Clover is more acid sensitive than grass.