Fertilizer and lime recommendations based on soil tests: Good, but could they be better?

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Abstract
Most fertilizer (and lime) recommendations are based on: i) a level of available nutrient (or pH) sufficient for at least near‐maximum crop yields and ii) an average rate of buildup of the available nutrient (or pH) per unit of fertilizer (or lime) added. Soils differ widely in the rate of buildup of available nutrient per unit of added fertilizer. Soil type (or association) is generally not available for individual soil samples submitted for testing. Even if it were, research information is generally inadequate to adjust the recommendations with any great degree of accuracy on this basis alone. Thus it seems imperative that new tests and/or equilibrations for individual soil samples be developed to provide the information needed. Recent results by us and others seems to offer hope of success in such efforts. Lime and fertilizer costs are a substantial portion of the total production costs in modern farming. Thus, it is important that the rates recommended be the best possible for the individual soil, crop, and farming situation. The question of how good our current recommendations are is examined, as is that of how they might be improved with some possible refinements. In order to be brief, use is made of charts, most of which have appeared in previous papers.