Interpretation of Results
Following the actual soil test analysis by the laboratory, the results must be interpreted to be of any value. In general, recommendation guidelines for the amount of a nutrient to apply are most often based on a specific year or field soil test value and on an interpretation of research data collected for that specific soil test over a period of years. For nutrients such as P, K, and Zn, soil testing generally provides an index of the relative ability of a soil to supply a nutrient to the crop, not the amount of available nutrient present in the soil. For these nutrients, what soil testing does best is provide an estimation of the probability of obtaining an economical response if that specific nutrient is applied to the crop. Secondly, it offers a long-term approximation of the percent of maximum yield that will be realized if the nutrient in question is not applied. Soil testing does not accurately predict the specific rate of a nutrient (e.g. P, K, Zn) to be applied for optimum crop production in all situations.
Sound wheat fertility programs depend on a comprehensive soil testing program, accurate and appropriate procedures, reliable guidelines based on long-term research, and knowledge of how to refine guidelines into efficient and profitable fertility programs.