Sources of Agricultural Limestone
When comparing limestone from different suppliers, be sure to ask for the following information:
1. Type of limestone: Is it either calcitic or dolomitic? Calcitic limestone consists mostly of calcium carbonate. Dolomitic limestone is a mixture of both calcium and magnesium carbonates. Dolomitic limestone should be used on soils with a magnesium soil test of 100 ppm or less. It is an excellent and inexpensive source of magnesium for acidic soils. On soils with a magnesium test greater than 100 ppm calcitic or dolomitic limestone may be used.
2. Guaranteed Minimum Specifications: This will provide the per cent calcium, percent magnesium, neutralizing value, fineness rating and Agriculture Index.
3. Neutralizing value (NV): NV compares the ability of the limestone to neutralize acidity relative to pure calcium carbonate. It is expressed as a percent of calcium carbonate's ability to neutralize acidity. Relative to calcium carbonate, a value less than 100 is less effective, while greater than 100 are more effective. The NV generally increases as the calcium and magnesium content increases.
4. Fineness rating: To be effective limestone must dissolve. A limestone's fineness rating is a measure of its particle size distribution and is determined using sieves. Any material passing through a #60 sieve is consisted to be fully effective. Material that passes through a #10 sieve but not #60 is considered only 40% effective. Materials that do not pass through #10 sieve are considered ineffective.
5. Agricultural Index (AI): AI is an indicator of a limestone's ability to neutralize acidity. It is calculated using the neutralizing value and fineness rating. It can be used to compare the ability of different limestones to neutralize soil acidity. The higher the AI the more effective the limestone on an equal weight basis. The average AI of limestone sold in Ontario has been about 75.
For more information about limestone, managing soil pH with lime, neutralizing value, fineness rating, calculating the Agriculture Index and determining the amount of lime to apply can be found in OMAFRA Publication 811 Agronomy Guide for Field Crops, Chapter 9.
Suppliers of Agricultural Limestone
This supplier list does not imply any endorsement or recommendation by the Ontario Ministry of Agriculture, Food and Rural Affairs.
For specific questions regarding the limestone analysis or specifications, please contact the appropriate company for their latest analysis information.
158 Don Hillock Drive, Unit 12-13
6509 Airport Road
Haley Station, ON K0J 1Y0
601 County Road #14, R.R. # 5
For more information:
Toll Free: 1-877-424-1300