Diagnostic biases in DRIS evaluations on sweet cherry and hazelnut

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Abstract
Five hundred leaf analyses of sweet cherry and hazelnut leaves were evaluated to determine if biases in DRIS formulas could prevent the detection of some deficiencies or excesses. Both one‐equation and two‐equation calculation procedures were evaluated. The one‐equation approach has several disadvantages. The data imply that there are limits on minimum or maximum values that an index can obtain for some elements, but not for others. The range of index values obtainable varies considerably among elements. If the sum of DRIS indices, regardless of sign, is used as a criterion to identify imbalances, relative deficiencies or excesses for some elements are masked. These difficulties are lessened but not entirely eliminated with the original two‐equation procedure. Regardless of the calculation procedure the relationship between DRIS indices and the respective concentrations varied for the elements N, K, P, Ca, Mg, Mn, Fe, Cu, B, and Zn. Some indices are so dependent on the concentration of the element involved that a ratio based diagnosis would have little advantage over a sufficiency range diagnosis. Other elements have indices that are so dependent on the concentrations of other elements that the index is of little use in evaluating nutritional status. Although DRIS is a very useful diagnostic approach, it will not detect all deficiencies or excesses. DRIS serves best as a supplement to sufficiency range based interpretation; providing additional information when severe imbalances exist.

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