Zone Forge reads your Colorado soil test in Colorado's own calibrated language — the critical levels and rate logic come straight from Colorado — CSU Extension Crop Series Soil fact sheets (Olsen-P + Mehlich-3 dual calibration), not a national average.
Published source: Colorado — CSU Extension Crop Series Soil fact sheets (Olsen-P + Mehlich-3 dual calibration)
Colorado — CSU Extension Crop Series Soil fact sheets (Olsen-P + Mehlich-3 dual calibration). Zone Forge cites the publication on every recommendation.
Yes — the Colorado soil-test recommendation calculator is free and needs no signup. Enter your lab values for source-cited P, K and lime guidance.
Zone Forge reads every Colorado soil test in its own state's language, then builds source-cited fertilizer and lime recommendations and full variable-rate prescriptions. See the science →