v1.0 (2026-05-23) · Colorado State University Soil, Water & Plant Testing Lab. CSU does not publish a buffer-pH lime method. Routine reports include **% free lime (CaCO3)** as a Low/Medium/High classification — measuring alkalinity, not buffer-pH for liming. CSU uses AB-DTPA (ammonium bicarbonate-DTPA) extractant designed for calcareous/alkaline soils. Colorado cropland is almost universally alkaline (pH 7.2-8.3). The only natural acid soils are in high-elevation forested mountain settings (parts of the western slope above ~8,000 ft on granitic / conifer-litter parent material) — not typical cropland.
This source publishes a state method — its crop-specific rate tables are maintained in the extension bulletin rather than a fixed crop list, so Zone Forge doesn't claim a crop set here.
Alkaline-region advisory. Zone Forge follows the state's extension guidance that lime is rarely needed on these alkaline soils.
Yes — Zone Forge's calculators are free and need no signup. This page shows the states and crops Colorado — alkaline-soil region (lime rarely needed) covers so you can verify the source behind your recommendation.
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