HOW DOLOMITIC LIME WORKS TO MAXIMISE SOIL RETENTION

Dolomitic lime is a natural mineral composed primarily of calcium magnesium carbonate. As such, it plays an essential role in agriculture, especially in soil health, where it acts to provide a pH balance in the soil, improve soil structure, and boost nutrient retention.

Nutrient retention is critical for optimal plant growth, as it ensures that nutrients in the soil remain available for uptake rather than being leached away. Through its ability to buffer against pH changes and prevent aluminium toxicity, dolomitic lime improves the availability and longevity of nutrients in soil, thus promoting sustainable, high-yielding agricultural systems.

Neutralising Soil Acidity

• Soils that are too acidic create an unfavourable environment for plants to take up nutrients. Acidic soils, typically those with a pH below 5.5, increase the solubility of harmful elements like aluminium and manganese, which can become toxic to plants and hinder the uptake of essential nutrients such as calcium, magnesium, phosphorus, and potassium.
• The importance of dolomitic lime lies in its calcium carbonate content, which acts as a neutralising agent, raising pH balance to the optimal range of 6.0 – 7.5 where nutrient availability is maximised.
• When dolomitic lime reacts with the acids in the soil to increase pH, it releases calcium and magnesium, which replace hydrogen ions in the soil solution. This reduces soil acidity and creates a more stable soil environment.
• In turn, this supports better nutrient retention because fewer nutrients are leached away in the presence of excess hydrogen ions. This ensures that essential nutrients will remain available to plants in a form they can absorb.

Providing Essential Calcium and Magnesium

Dolomitic lime is unique in that it supplies both calcium and magnesium. These two critical nutrients for plants play a role in cellular structure, enzyme activation, and chlorophyll production. 

• Calcium improves soil structure by promoting flocculation, the process by which soil particles bind together into aggregates. Good soil aggregation leads to improved porosity, allowing for better water retention and reducing the likelihood of nutrient leaching.
• Calcium’s role in soil particle aggregation enhances the retention of nutrients because better-structured soil holds onto nutrients more effectively and helps maintain a balanced root environment.
• Magnesium, on the other hand, is a central component of the chlorophyll molecule, essential for photosynthesis. In acidic soils, magnesium is often deficient, hindering plant growth and limiting nutrient uptake efficiency.
• By adding magnesium directly through dolomitic lime, plants have better access to this element, and the balance between calcium and magnesium further supports soil nutrient retention.

 Buffering Capacity and Soil Cation Exchange Capacity (CEC)

• One of the essential mechanisms through which dolomitic lime maximises nutrient retention is by improving the soil’s buffering capacity. Buffering capacity is a soil’s ability to resist changes in pH, which is crucial for nutrient stability.
• When dolomitic lime is applied, the calcium and magnesium ions it releases increase the soil's Cation Exchange capacity (CEC). CEC is a measure of a soil’s ability to hold and exchange positively charged ions, or cations, which include essential nutrients like potassium (K⁺), calcium (Ca²⁺), and magnesium (Mg²⁺).
• By boosting CEC, dolomitic lime helps soil retain a greater quantity of these essential nutrients, as soils with higher CEC can hold onto nutrients and prevent them from leaching out due to rainfall or irrigation. This also means nutrients are more readily available to plant roots, allowing for continuous access rather than sporadic absorption.

Reducing Nutrient Leaching and Improving Water Retention

• The application of dolomitic lime can prevent nutrient leaching, especially in sandy soils or soils subject to heavy rainfall. Leaching is a process where nutrients dissolve in excess water and are carried below the root zone, becoming inaccessible to plants.
• The calcium in dolomitic lime improves soil structure and aggregation, reducing the risk of leaching by ensuring that water and nutrients are held in the root zone where they are needed.
• Improved soil structure also benefits water retention, allowing for a more even distribution of nutrients and preventing sudden losses of essential elements. This is especially beneficial in dry conditions, where the retained moisture helps reduce the frequency of nutrient losses. Improved moisture retention also creates a balanced environment where plants can thrive and absorb nutrients consistently over time.

 Reducing Aluminium Toxicity

• In highly acidic soils, the increased solubility of aluminium can lead to aluminium toxicity, which harms plant roots and restricts the uptake of other essential nutrients. Dolomitic lime can mitigate this toxicity.
• When it neutralises soil acidity, dolomitic lime reduces the availability of free aluminium ions in the soil solution. This allows plants to develop healthier root systems capable of better nutrient absorption.
• Additionally, without the interference of aluminium, other nutrients are absorbed more efficiently by plant roots, thus maximising the effectiveness of fertilisers and any organic matter in the soil.

Enhancing Microbial Activity and the Breakdown of Organic Matter

• Dolomitic lime supports microbial life, ensuring a steady release of nutrients from organic sources.
• Soil microorganisms play a vital role in nutrient cycling, decomposing organic matter, and converting nutrients into plant-available forms. However, acidic soils can suppress microbial activity, reducing the soil’s capacity to decompose organic material effectively.
• To the rescue comes dolomitic lime which, by raising the pH, creates a more favourable environment for beneficial microbes to thrive. This in turn, helps to break down organic matter more efficiently.
• The breakdown of organic matter releases nutrients such as nitrogen, phosphorus, and sulphur – all of which are essential for plant growth. Healthy microbial activity also aids in forming humus, a stable form of organic matter that improves nutrient and water retention. 

Lime Sales: Bringing health back to Southern African soil

Lime Sales is one of the leading producers and suppliers of dolomitic limestone products in the Western Cape. Meeting the highest industry standards, we supply dolomite and gypsum to the agricultural, construction and civil construction industries. 

Exceptional year-on-year growth since inception in 2003, has advanced the company to become the supplier of choice to the agricultural lime and gypsum market in Southern Africa.

We are committed to producing products that meet the needs of our customers and are in specification according to law. Have a look at our latest product analysis for our Bridgetown Dolomite.

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