v1.3 (2026-08-23) · University of Tennessee Soil, Plant and Pest Center (UTIA) nutrient recommendations. UT publishes BOTH Mehlich-1 (default) and Mehlich-3 calibrations — W229 specifically converts between the two extractants. UT's M3 critical thresholds DIVERGE from Penn State: TN cuts off P recommendations at M3 31-60 lb P/A (High) where Penn State still recommends. Cotton K thresholds are significantly higher than corn/soybean K thresholds (cotton at L through M3 178-356 lb K/A vs non-cotton 115-203). Stops at 'High' — does NOT recommend P/K at H or VH (more conservative than Tri-State 2020). Includes cotton; row crops only. Lime is handled via the Coastal Plain Adams-Evans source (separate); this source covers nutrient recommendations only.
State extension method. Zone Forge computes this source's supported nutrient rates in-app and cites the published method.
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