How much lime per acre?

How it works

The math — no black box.

Lime rate is driven by your soil's reserve acidity, not its measured pH alone. The lab measures reserve acidity several ways depending on your state's extension method — exchangeable acidity, a buffer-pH reading, reactive aluminum, a Ca(OH)₂ titration, even pH × soil texture. This calculator ships all 50 states' methods and applies whichever one your state's land-grant publication actually uses, auto-selected the moment you pick your state. Two of the 50 — to show how different they are:

Penn State (Mehlich Buffer / Exchangeable Acidity) — the method Penn State publishes today. Penn State retired the older Adams-Evans buffer-pH method a few years back; the AASL lime recommendation is now driven by the Mehlich Buffer test, reported on the soil-test report as "Acidity" in meq/100 g. We look up your acidity in the published table at the pH-goal column matching your crop, then convert lb CCE/ac to tons.

Iowa PM 1688 / Tri-State 2020 (buffer-pH crosswalk) — both bulletins publish lime in print form via SMP buffer or pH+CEC tables, and midwest labs commonly report a buffer pH directly. The crosswalk in our engine maps that buffer pH to tons CaCO₃-equivalent per acre.

Either way, we then divide by your product's ECCE rating to get the actual tons of physical product per acre. Most online lime calculators skip ECCE. That matters: a 70% ECCE product needs ~43% more tons-per-acre than a 100% ECCE pelletized lime to deliver the same neutralizing capacity. Get this wrong and you'll over- or under-apply by a third.

Same engine, three places

This calculator runs on Zone Forge's production lime engine — the same Python module that generates variable-rate lime prescriptions for the John Deere Operations Center push, and the same one our in-app AI chat assistant calls when you ask about a specific sample. One math, one citation, three surfaces.