Soil test is key to get full value

Factors affecting how much lime to apply

We have discussed in previous weeks the importance of lime in boosting productivity in both our pastures and cropping systems. However, liming can be an expensive procedure and therefore getting the most value from the lime you apply is important. This raises the question of how much lime to apply?

The best way to accurately calculate how much lime to apply is a soil test. The amount of lime required to counteract soil acidity depends on a number of factors such as the existing soil pH; desired or target soil pH; soil texture and lime quality. The one one factor the grower does have over the application process is choosing the highest quality lime for the job.

All liming materials vary – the three main factors to look out for are as follows:

Fineness

This is a major influencing factor in how quickly the lime will react in the soil. The finer particles have a greater surface area to react with the soil.

The larger number of fine particles the better the lime can be distributed through the soil, resulting in a quicker reaction. The finer the lime the quicker it will react, however finer particles are often difficult to spread.

Therefore a mixture of fine and coarse particles will overcome spreading difficulties. Aim to spread lime with particles no greater than 0.3mm.

Neutralising Value

The NV is the capacity of the lime to neutralise the acidity in the soil. The higher the NV the more effective the lime will be.

NV is calculated from a standard which is pure calcium carbonate (or pure lime) and this will have a NV of 100.

When purchasing lime aim for lime which has a NV of 95.

Calcium and Magnesium

Every lime sample will have varying levels of Ca and Mg. Products such as Ag Lime, Dolomite, Magrilime will have different ratios of Ca:Mg and may be suitable in some instances.

The choice of product for crops or pastures depends primarily on the price and requirement for Magnesium.

The best way to identify if magnesium is required is through soil testing and or plant tissue testing in some instances.

As always if you would like a lime sample tested or a test analysed please don’t hesitate to bring them into AgnVet.

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