Agricultural lime

Agricultural lime is produced by crushing and grinding limestone rock. Calcitic lime is predominantly calcium carbonate, while dolomitic lime contains both calcium and magnesium carbonate in varying proportions depending on the source rock. Its neutralising value and fineness of grind both affect how effectively and quickly it reacts in soil.

Calcitic lime

Predominantly calcium carbonate (CaCO₃)

Dolomitic lime

Calcium and magnesium carbonate (CaMg(CO₃)₂), source rock-dependent

Neutralising value

A laboratory measure of a lime product’s acid-neutralising capacity relative to pure calcium carbonate

Fineness of grind

Finer particles react faster; coarser particles react more slowly over a longer period

Agricultural lime supplies calcium, and magnesium in dolomitic forms, though these releases occur gradually as the carbonate reacts with soil acidity rather than as an immediately soluble nutrient dose. Its main agronomic function is neutralising acidity rather than supplying nutrients on a comparable timescale to soluble fertilizers.

• Calcium is released as the carbonate reacts with soil acidity
• Dolomitic lime additionally supplies magnesium over the same timeframe
• Not a source of nitrogen, phosphorus, or potassium

Agricultural lime is applied to raise the pH of acidic soils toward a range that improves nutrient availability and reduces aluminum and manganese toxicity risk, benefiting acid-sensitive crops such as alfalfa and soybean, and is chosen as calcitic or dolomitic depending on whether soil testing indicates a magnesium need alongside the pH correction.

• Raises soil pH, improving availability of several macro- and micronutrients on acidic soils
• Reduces aluminum and manganese toxicity risk on strongly acidic soils
• Dolomitic lime is chosen where soil testing also indicates a magnesium need

Lime rates are generally determined from a soil test that accounts for both the current pH and the soil’s buffering capacity, since two soils at the same pH can require different lime rates depending on clay and organic matter content. Because lime reacts slowly, applications are typically made well ahead of the crop that needs the corrected pH.

Appropriately applied lime generally has limited direct environmental downside beyond the resources used in mining, grinding, and transport, though over-liming can push pH excessively high and reduce availability of iron, zinc, manganese, and phosphorus in the same way that naturally alkaline soils can.