Evaluation of DRIS for Judging the Nutritional Status of Hazelnuts

Abstract

Abstract The Diagnosis and Recommendation Integrated System (DRIS), which uses nutrient element concentration ratios as indicators of nutrient deficiency, was used to evaluate current sufficiency ranges for hazelnut trees. Reference values that were derived from published and unpublished field data were used to calculate DRIS indices for N, P, K, Ca, Mg, Mn, Fe, Cu, B, and Zn. A nutritional imbalance index (NII) was computed as the sum of DRIS indices irrespective of sign, and a threshold NII value (mean NII + 1 SD), above which severe imbalances are expected, was established. DRIS diagnoses were then compared with the sufficiency range approach to determine if relative deficiencies or excesses associated with severely imbalanced trees would have been routinely detected in 624 mineral analyses of hazelnut leaves. A previously published field trial was also reevaluated. DRIS diagnosis generally agreed with the diagnoses made by the sufficiency range method, especially if sufficiency ranges for some elements were made more narrow. However, some nutrients were never identified by DRIS as a major relative deficiency or excess in any of the trees judged severely imbalanced, based on the sum of DRIS indices. Nitrogen and Mg deficiencies were not detected unless lower NII thresholds were used. Unfortunately, lowering NII thresholds enough to detect N and Mg deficiencies identified some high-yielding trees as severely imbalanced. DRIS will not detect all deficiencies or excesses. Therefore, DRIS is best viewed as a supplement to sufficiency range diagnoses that provides additional information when severe imbalances are detected.