• Why is it important to me as a farmer?
• How and why are limes different?

• Selecting the most appropriate lime

• Limes vary in their ability to reduce acidity
• Limes should be applied on the basis of soil test analyses and purchased on the basis of effective neutralising values (ENV) or neutralising value (NV) and cost

• Limes from Southern Victoria are generally �softer� and tend to partially dissolve in water compared with �harder� limes of other regions, such that there is less need to incorporate these with cultivation or have them ground finer

• Knowing characteristics about lime allows you to compare the cost-effectiveness of a variety of lime products and purchase the produce that will be most cost-effective for your farm

• Lime or limestone (calcium carbonate) is a naturally occurring rock that is used to raise the pH of acid soils. The amount of lime required to increase the pH of a soil by one pH unit depends on the buffering capacity of the soil. The buffering capacity is a measure of the soil�s ability to resist change in pH. A well-buffered soil becomes acid more slowly than a weakly buffered soil, but will require more lime to increase the pH value
• Generally, you need to use lime that is in very small particles so it will react quickly with the soil, this is called the finesse of the lime and is measured by the limes Effective Neutralising Value (ENV)
• Effective Neutralising value (ENV) is a measure of the effectiveness of the neutralising substances. So, the higher the ENV, the more effective the lime will be at increasing pH
• However, as the �softer� limes from southern Victoria are more soluble than the �harder� limes of other regions, the NV is a better indicator of neutralising value than ENV
• Liming materials are compared to pure calcium carbonate. For the purposes of comparison calcium carbonate is given a neutralising value of 100; ideally NV should be over 95
• Lime manufactures have to specify the percentage of particles finer than 0.25 mm (a quarter of a millimetre in diameter). Very fine lime has 98-100 per cent fines (as they are called) and this is the grade you are recommended to buy (Refer table 1). The percentage is marked on the bag or invoice
• The Fertiliser Regulations 1995 have set the following standards for lime and liming materials (on a dry matter basis):
  • Grade 1 lime must have a minimum ENV of 80
  • Grade 2 lime must have a minimum ENV of 65
  • Grade 3 lime must have a minimum ENV of 50

Differences in Limes

By type of lime products:

• By-product and natural limes contain calcium carbonate (CaCO3), calcium hydroxide (Ca(OH)2), or calcium oxide (CaO). Dolomitic limes contain magnesium carbonate (MgCO3) in addition to the CaCO3. Pure lime is 100% calcium carbonate (CaCO3)
• Agricultural limestones usually occur, in Victoria, in limestone rock deposits with calcium carbonate (CaCO3) contents ranging from 48% to 97%. Agricultural lime is the most commonly used product for increasing soil pH in pastures and is usually the most cost-effective. Limes from Southern Victoria are generally �softer� and tend to partially dissolve in water compared with �harder� limes of other regions
• Burnt lime (also called quick lime) is calcium oxide (CaO). It is a faster-acting lime and has the highest neutralising value. This lime is mostly used in horticultural enterprises and is not usually applied to pastures
• Slaked lime (also called hydrated lime or builder�s lime) is calcium hydroxide (Ca(OH)2) and has a higher neutralising value than agricultural lime but is more expensive and not usually applied to pastures

Differences in Limes

By type of lime products: (continued)

• Lime kiln dust is the very fine dust (particle size of less than 0.1 mm) produced by kilns used to burn lime. It contains both limestone and burnt lime and is difficult to handle due to its fineness, so a contractor experienced in spreading the product should be used. Cement kiln dust has similar properties, plus it can contain significant amounts of potassium (commonly 3% to 5%)
• Wet lime is also known as liquid lime. The effectiveness of liquid lime is determined by its NV, not its ENV. There are extra handling costs with wet lime. Wet lime is not usually applied to pastures
• Dolomite is a mixture of calcium carbonate and magnesium carbonate (CaCO3 and MgCO3). As the magnesium carbonate content of limestone increases, it is firstly called dolomitic limestone and finally dolomite (pure magnesium carbonate). The Limestone Association of Australia defines dolomite (as a product) as having a minimum magnesium carbonate analysis of 28% and a minimum calcium carbonate analysis of 35%. Dolomite is frequently used in horticulture as a source of magnesium (for example, in orchards) and is sometimes used on pastures.

Dolomite is used as a source of magnesium for magnesium-deficient soils. It can also be used as a source of magnesium for livestock. However, very high rates are required for this purpose (5 t/ha or greater). A Department of Agriculture study at Camperdown showed that 12.5 t/ha needed to be applied to obtain an effect. Experience is that dolomite is generally not effective in reducing grass tetany, and livestock should be treated directly

By ENV:


• The lime analysis prepared for the following survey is indicative of the lime quality at the time of sampling. However, because lime quality can vary due to changes in the area or depth mined or the degree of crushing, the analytical results of future lime samples from the same company may vary. If you are concerned about lime quality, samples can be submitted to a laboratory for testing

Table 1 - Lime survey results (2001). Source: DEPI Victoria

• By comparing lime products through cost differences:
  • When you compare lime products, make sure that you select the most economical product available in your region. The value of limes of various types and from various sources can be compared by making the following calculations:
  • First, gather quotes from suppliers for the total cost per tonne to have various limes applied to the paddock (including the purchase price and the transport and spreading costs)
  • Second, obtain the effective neutralising value for the limes. Most limes on the market have been tested to determine their ENV, and this information should be available from the supplier. This will provide a �per unit� basis for comparison. For the �softer� limestones in Southern Victoria, the NV is more useful than the ENV
  • Finally, divide the total cost by the effective neutralising value of each product:
    
    Unit cost =Total cost per tonne spread / ENV

Example:
Say that there are two lime products available in your area:
• Lime A has an ENV of 95 and costs $60/t spread
• Lime B has an ENV of 70 and costs $50/t spread

Which is more economical?
• Lime A: $60 divided by 95 = $0.63 per unit of ENV (as received basis)
• Lime B: $50 divided by 70 = $0.71 per unit of ENV (as received basis)
• Lime A is the lower cost lime to use based on its effective neutralising value and the total price

• Knowing these characteristics about lime (including dolomite) allows you to compare the cost-effectiveness of a variety of lime products and purchase the produce that will be most cost-effective for your farm. However, you must also take into account other considerations, including the handling requirements of some products

• Use the following online lime calculators:
  • Lime Comparison Calculator - Soilquality.org.au
    
    The lime cost calculator allows you to compare the total cost (lime, freight and spreading) per hectare for the equivalent of 100% neutralising value (NV) of lime
  
  
  • Online Lime Calculator - Aglime of Australia

Figure 1 - Limes ain�t limes! When taking the ENV into account, the unit cost of the products differ significantly. - Source: HDLN, 2008    [View larger image] 

• When and why should I need to apply lime?
• How do I manage the impact of sodic soils?

• Managing Soil Factors That Can Limit Plant Growth - Department of Environment and Primary Industries, Victoria


• Soil Acidity - South West Victoria SoilSmart Series. Clarkson (2003)� Corangamite CMA Soil Health Outputs

• Managing Soil Factors That Can Limit Plant Growth. Department of Primary Industries, Victoria.
• Clarkson T (2003). Soil Acidity. South West Victoria SoilSmart Series � Corangamite CMA Soil Health Outputs.

Page Updated: September 2013
Produced by AS Miner Geotechnical