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Liming Guide for Sandy Loam Soils

 

Lime in 2 Stages

 

Rehabilitation   Maintenance
Apply 2 t/ha of Aglime every 3 or 4 years to bring the topsoil and subsoil pH up to the desired level   Apply 1 t/ha of Aglime every 6 to 12 years to maintain soil pH around the desired level.

 

Topsoil pH

In soils which do not have a potential subsoil acidity problem, topsoil pH is best maintained around 5.0 to 5.5 for most crops and pastures to ensure adequate nutrient availability and to prevent aluminium toxicity.

 

Subsoil pH

Subsoil pH should be at least 4.5 for a wheat lupin or wheat subclover pasture rotation and over 5.0 for most other crops or pastures to prevent yield loss from aluminium toxicity.

To increase the pH in the subsoil, the topsoil needs to be limed to at least 5.5. This provides sufficient Aglime to leach into the subsoil and treat the acidity.

Ideally, for optimum efficiency, liming should begin many years before subsoils reach pH 4.5 to 5.0. This is due to the time needed for Aglime to leach from the topsoil into the subsoil and treat the acidity.

 

Effect of Liming

On most acid soils, the first tonne/ha of Aglime treats the topsoil, making phosphate more available, increasing microbial activity to release more nutrients (especially nitrogen) from organic material and also stopping aluminium toxicity.

The 2nd and 3rd t/ha begin to leach and treat subsoil acidity where aluminium toxicity can have a relatively greater effect by reducing root growth.

 

Monitor

Test pH in both the topsoil and subsoil every 4 or 5 years and adjust liming rates if necessary.

 

Rates

We recommend Aglime is applied at regular rates of 1t/ha until top and subsoils have reached the required levels.

 

1 t/ha of Aglime increases pH in 10cm depth of soil by around

0.7 units in sandy loam

0.4 units in loam

0.2 units in clay

 

Note: Higher rates or more regular liming are needed to change subsoil pH levels. Acid loam and clay soils also require higher rates or more regular liming than shown in the diagram.

 

As the topsoil pH increases above pH 5.5 there is less free acid in the soil to act on applied Aglime. As a result, less Aglime dissolves and pH increases at a slower rate.

 

However, the undissolved Aglime in the topsoil is leached to treat acidity in the subsoil ensuring optimum use of every applied tonne of Aglime.

 

Remember

Aglime of Australia provides free soil pH testing for clients.

Precision SoilTech, part of the building better soils group, provides a soil sampling service backed by GPS site location to more accurately monitor your soil pH changes in the top and subsoil.

Use these services to help make better decisions on liming.