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