Rethinking Recommendation Philosophies and Benefits to Regional Approaches for Soil Test Recommendations.

Fertilizer recommendation philosophies or approaches used by most states for phosphorus (P) and potassium (K) fall into one of two main categories; sufficiency level approaches designed to optimize yields for a single crop year, or build up and maintenance approaches designed to build soil test values to a non-limiting level in a finite time period. Both approaches are relatively prescriptive in nature in most states and fail to account for differences between land ownership and land tenure and they do not allow for a risk based approach for crop fertilization. Significant changes in fertilizer recommendations for similar crop and soil systems occur abruptly at state boundaries and the data to support these differences are often more than 20 years old. In addition, fertilizer recommendations have become increasingly regulatory in nature for some producers. Fertilizer recommendation “jargon” (i.e. critical level) is not uniformly defined across states. A more flexibly recommendation system that allows for differences in fertilizer rate guidelines based on cropping system, physiographic region, producer objectives, risk and land tenure would likely be more widely accepted by producers.