Zone Forge reads your Iowa soil test in Iowa's own calibrated language — the critical levels and rate logic come straight from Iowa State PM 1688, not a national average.
Per Iowa State PM 1688 — below the critical level, a yield response to the added nutrient is expected.
Published source: Iowa State PM 1688
Iowa State PM 1688. Zone Forge cites the publication on every recommendation.
Yes — the Iowa 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 Iowa soil test in its own state's language, then builds source-cited fertilizer and lime recommendations and full variable-rate prescriptions. See the science →