The importance of lime application

June 2025

SOIL PH

Everybody has suffered from heartburn or indigestion at some point in their lives. This is usually a result of excessive stomach acids. When this happens, a person feels uncomfortable. To feel better, you use antacids to neutralise the acid. You are only able to function at your best again when the discomfort subsides.

Soil is almost like your stomach – it uses water to break down (digest) all the organic and other fertiliser material available. This enables the plant to absorb the nutrients. If there is too much acid in the soil, the plant is unable or unwilling to extract the nutrients (phosphates).

Over time, the application of chemical fertilisers, together with the plant’s extraction of various soil nutrients, causes the acidity to rise. Tillage practices also play a role in the pH levels. When the soil is turned, as in ploughing, the natural processes of the organic elements in the soil are disturbed. This affects natural decomposition, which in turn can affect the acidity. Other factors that could affect the pH are high rainfall, high yields, soil types, insufficient/excessive or incorrect fertiliser, and the type of crop planted.

So, just like people’s stomachs, when necessary, you need to remedy the situation and apply an antacid to the soil – lime. There are two different types of lime – agricultural or calcitic lime, which is more generally used, and dolomitic lime, which is applied to soil with a magnesium deficiency. The experts who do the soil analysis will be able to advise you about the right type of lime and how much to use on each land. 

Lime reacts much slower than fertiliser and should be applied and worked into the ground before tillage. It can be applied at any time of the year, but preferably it should happen long before planting, when lime can be given a chance to react in the soil. However, the optimum benefits are experienced over the long term and are usually only seen in the following seasons.

The correct soil pH is the foundation on which farmers build their crops. A weak foundation is a recipe for a long-term disaster. Without water, a plant cannot survive, but nothing survives on water alone – with an acidic foundation, the plant is unable to absorb the nutrients, no matter how much water is available.

The only way to determine the acidity and the remedy required is through soil analysis. If the lime requirement is excessive for a single application, it may be necessary to apply lime over a two-year period. Once the required pH is achieved, it is essential to ensure that the optimum levels are maintained – allowing the farmer to evaluate the soil every alternate year, or after an unusual yield or rainfall season.

Remember, lime application is not a quick fix. The benefits are only evident over the long term, provided that the pH levels are maintained at an optimum level each season. 

References
https://www.grainsa.co.za/application-of-lime---food-for-thought
https://www.grainsa.co.za/upload/article_pdfs/Pula_Imvula_June_2014_English.pdf

Publication: June 2025

Section: Pula/Imvula