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Mississippi State University — Nutrient Management Guidelines (Lancaster extractant)

v2.2 (2026-08-23) · Mississippi State University Extension Soil Testing Laboratory nutrient recommendations (MSU Extension Publication P2647, Nutrient Management Guidelines for Agronomic Crops Grown in Mississippi). MSU uses the Lancaster (Mississippi) extractant — a proprietary two-step extraction that has NO published Mehlich-3 conversion. This is why Mississippi cannot be routed to Penn State or Iowa for nutrient recommendations: a Lancaster value flowed into a Mehlich-3 critical level produces wrong rates. The published method is a CATEGORICAL bracket table, NOT build-to-target: P2647 Table 2 rates soil-test P (lb P/A) into 5 indices (Very Low/Low/Medium/High/Very High) and prescribes a fixed lb P2O5/A per index per crop; soil-test K is rated through CEC-stratified Tables 3a/3b/3c (the K bracket depends on the soil's CEC) and each index prescribes a fixed lb K2O/A per crop. No P/K is recommended at High or Very High. Lime is handled via the Coastal Plain Adams-Evans source (separate); this source covers nutrient recommendations only.