In the interest of saving money or finding a use for waste materials, many farmers ask about the possibility of using by-products as a substitute for limestone. Some suppliers will tell the farmer the calcium carbonate equivalent of the material. Pur e calcium carbonate has a calcium carbonate equivalent of 100 and is used as the bench-mark by which all other materials are compared.
If the soil test report calls for 1 ton of lime per acre, it is assuming that you are using state certified calcitic or dolomitic limestone which has a calcium carbonate equivalent of about 100. If you use another material that has a calcium carbonat e equivalent of 50, then it has only half of the soil acid neutralizing value of calcitic or dolomitic limestone and, therefore, twice as much (in this case 2 tons) should be applied. If you have a material that has a calcium carbonate equivalent of 150, then you need only 67% or 2/3 as much of this material on your fields as regular limestone. If you know the calcium carbonate equivalent of any material, just divide 100 by that number (100÷X) and multiply it times the lime recommendation of the so ils report to determine the amount you need to apply per acre.
As an example of the calcium carbonate equivalent of some commercially available materials, calcium oxide, also known as quick lime or burnt lime has a calcium carbonate equivalent of at least 140. Calcium hydroxide, also known as slaked lime, hydrate d lime, or builder's lime has a calcium carbonate equivalent of at least 110.
Many materials that are a by-product of some other manufactured material can vary greatly in the calcium carbonate equivalent. For this reason it would be wise to question the supplier to insure that the material was properly sampled and sent to a ce rtified laboratory. Also material that is very coarse can have a high calcium carbonate equivalent but will take several months to completely break down and be adequately effective. When appropriate, EPA guidelines should be followed when materials cont ain heavy metals.
Your choice of alternative liming materials will then be based on your confidence in the claimed liming value of the material (as expressed by the calcium carbonate equivalent and its fineness) and the possible savings if used in place of commercial do lomitic limestone.