By Stephen Campbell and Robert J. Van Saun et.al
The saying "there’s no such thing as a free lunch" comes to mind when talking about free lime. Over the last couple of months, I've received a few phone calls and heard conversations from farmers who have been using lime from an industrial plant as a free byproduct. However, before you load the spreader and cover your fields, it's worth asking: What's actually in that product, and how effective is it as lime?
In Pennsylvania, agricultural lime is regulated under the Pennsylvania Fertilizer, Soil Conditioner, and Plant Growth Substance Law. This law requires that any lime sold or distributed for agricultural use be registered with the Pennsylvania Department of Agriculture. Certified products must undergo laboratory testing for fineness (sieve analysis), calcium carbonate equivalency (CCE), and the detection of potential contaminants. Heavy metals are also tested to ensure the material is safe for crop production and will not cause long-term issues in the food chain. Only products that meet these standards can legally be sold or distributed as agricultural lime in the state.
That's why testing is so necessary when dealing with byproducts or "free" lime sources. Earlier this year, a sample of one such byproduct was analyzed, and the results showed that it would take nearly twice the application rate—and twice the tractor time—to deliver the same neutralizing power as certified ag lime.
Source : psu.edu