Overview

This agriculture limestone supplier list does not imply any endorsement or recommendation by the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA). It is a listing of companies that have requested to be added to the list. To be included, contact the OMAFRA Agricultural Information Contact Centre.

Information to consider before you buy

Type of limestone

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.

Guaranteed minimum specifications

Guaranteed minimum specifications will provide the calcium percentage, magnesium percentage, neutralizing value, fineness rating and Agriculture Index.

Neutralizing value (NV)

NV compares the limestone’s ability 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 a value greater than 100 is more effective. The NV generally increases as the calcium and magnesium content increases.

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 considered 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.

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.

Find out more information

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 OMAFRA.