v1.2 (2026-06-04) · University of Arkansas Soil Testing & Research Laboratory (Marianna, AR) — combined lime + nutrient source. Lime uses Arkansas's distinctive pH+Ca lookup (no buffer); nutrients use MP197 Ch5 (soybean) and MP192 Ch9 (rice) P/K critical-level + crop-specific N tables. Mehlich-3 extractant at 4-inch depth for soybean+rice (NOT 6 or 8 inch — Arkansas-specific due to hardpan); 6-inch for corn+cotton. ppm × 2 = lb/ac (acre furrow slice convention).
State extension method. Zone Forge computes this source's supported nutrient rates in-app and cites the published method. Its published lime method is computed in-app too.
Yes — Zone Forge's calculators are free and need no signup. This page shows the states and crops University of Arkansas — pH+Ca lime + Mehlich-3 nutrient recs covers so you can verify the source behind your recommendation.
Browse the full Coverage Explorer — every state, crop and source — or see the science →