An Evaluation of the DRIS Approach for Identifying Mineral Limitations on Yield in ‘Napolean’ Sweet Cherry

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Abstract
The ratio-based Diagnosis and Recommendation Integrated System (DRIS) was used to evaluate the mineral status of ‘Royal Ann’ sweet cherry trees. Standard ratios were developed from experimental research plots and then applied to evaluate the nutritional status of a large number of trees in a commercial orchard. DRIS indices for each element were calculated from a formula, which included DRIS standard ratios, their standard deviations, and the observed ratios from the sample being calculated. Nutritional Imbalance Indices (NII) were compared as the sum of DRIS indices irrespective of sign. By selecting a sufficiency range that produced the best agreement with DRIS evaluations, independent sufficiency ranges were derived from the commercial orchard data. Trees with high NII were consistently low-yielding, and, in mulching treatments where unfavorable NIIs were improved, yields were increased. The NII was more strongly correlated with relative yield increases than any other mineral parameter. The data imply that it is possible to develop useful DRIS standards and DRIS-derived sufficiency ranges from survey data, even though conventional statistical approaches do not reveal strong relationships between mineral concentration and yield.

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