1. Updating Soil-test Phosphorus and Potassium Calibrations for Wisconsin

Effective soil-test interpretations and fertilizer recommendations require phosphorus (P) and potassium (K) soil test to be field correlated with crop yield response to fertilization and calibrated to identify response probabilities. Only the Bray-1 soil test is calibrated to provide P and K interpretation guidelines in Wisconsin, with supporting trials being over 30 years old. This study correlated the P extracted by the Bray-1 (BP), Mehlich-3, Olsen-P (OP), and H3A tests and K extracted by the... C.A. Laboski, F.J. Arriaga, J.D. Jones