The most cost effective lime will be the lime that increases soil pH the most relative to the total cost of liming (lime + freight + spreading). The dominant cost component of liming is freight, so you want a smaller amount of a higher quality product to reduce the overall cost.
Contrary to some current marketing, there are only two issues that determine quality, or lime effectiveness per tonne: Neutralising Value and Particle Size.
The Neutralising Value of a lime represents the purity of a lime, based on a scale of percentage calcium carbonate (pure lime). A lime with a NV of 90% will be 50% more effective than a lime with a NV of 60%, given the same particle size distribution.
There is no conclusive research that calcium is an issue in the liming process. Even though Aglime is 34% Ca, and due to the fine particle size is very 'plant available', the calcium component of a lime does not contribute to the effectiveness of a lime.
Investigate for yourself
Before buying a lime, find out exactly what what you are purchasing. Look at the specification sheets for the particle size distribution and neutralising values. Do the sums. If looking at a blend, find out the proportions of the different ingredients and look at the specification sheets for the different components. Look at what you are really paying for; are you better off buying the components separately?
In the example on the left, for the same amount of lime, the finer lime has neutralised 9 times more soil than the coarser lime. The change in pH from the finer lime will be much larger than from the coarser lime and this is proven in field studies and from farmers’ own experience.
Limes dissolve in soil by acid eating away the surface of the lime particle. When the acid attacks the surface of the lime, carbonate is released and that neutralises the acid. As a result, the soil next to the lime particle is neutralised and can’t dissolve any more lime. The lime particle sits in a pocket of neutralised soil and is no longer effective.
Don’t be fooled into comparing limes by shaking them in liquid – the coarse lime particles continue to come in contact with fresh acid and so continue to dissolve – this doesn’t happen in the soil.
Lime particles under 0.5mm are the most effective in increasing soil pH.
Choose your lime based on particle size but also check the neutralising value of the fine particle fraction to ensure it is lime, not clay you are buying.
Online Lime Calculator
Try using our Online Lime Calculator to determine what lime is the best lime for you. The lime calculator takes into account the total cost of liming including freight and spreading, and determines the total cost to induce a specfiic pH increase in the soil on your farm.