Development of standardized fertilizer recommendations for corn grown in the Mid-Atlantic region of the United States

Crop fertilizer recommendations often differ between soil test laboratories operating within a given physiographic region, due to differences in chemical method used, laboratory techniques, soil test interpretation, and philosophy of making recommendations. In 1998, the Mid-Atlantic Soil Testing and Plant Analysis Work Group, comprised of representatives from government (university/ state) and commercial/industrial laboratories, evaluated differences in corn N, P, and K fertilizer recommendations in an effort to achieve more uniformity. For P and K, comparisons were made for four popular extradants at key strategic soil test levels. These levels were 1) the "zero" extractable nutrient level to indicate the maximum amount of fertilizer recommended by each laboratory, 2) the soil test level of no further crop response to applied fertilizer (optimum/maximum yield) to indicate the maintenance fertilizer rate each laboratory was using, and 3) the soil test level above which no further fertilizer would be recommended. The extractable nutrient values each laboratory was using at each strategic soil test level were compared, and then a standard set of strategic soil test levels and fertilizer recommendations were developed. Regarding N recommendations, a range in application rates was selected for an appropriate target yield applicable to soils in the region. These recommendations were designed for gradual implementation by the laboratories in the work group.