Utilization of DRIS for Diagnosis of Nutrient Deficiencies in Winter Wheat 1

The diagnostic recommendation integrated system (DRIS) has been regarded by some to be capable of providing nutrient diagnoses via foliar analyses regardless of the origin or age of the plant. This study had two objectives designed to address this claim. First, to determine if nutrient ratio norms currently available for wheat ( Triticum aestivum L.), based on hard red winter wheat from Kansas, South Dakota, and Canada, could be used by the DRIS procedure to accurately diagnose deficiencies for N, P, K, and S in soft white irrigated winter wheat (cv. Daws) grown in central Washington state. Second, since DRIS diagnoses are based on a set of nutrient ratios assumed to be relatively invariate with age, to determine if a sampling date/time dependency existed for six specified nutrient ratios. Using the set of published DRIS norms developed from wheat grown in the Midwest, nutrient diagnoses calculated on irrigated winter wheat grown in central Washington tended to overestimate N deficiencies and underestimate P deficiencies at early heading and tillering, respectively, relative to parallel diagnoses by DRIS based on a corresponding set of norms. This second set of norms was derived from tissue analyses of winter and spring wheat grown on a Haploxeroll, an Argixeroll, two Argialbolls, and a Camborthid in Washington state. A statistical analysis of nutrient ratios from winter wheat grown in eastern Washington indicated that six ratios (N/P, K/N, K/P, N/S, P/S, and K/S) each exhibited significant sampling date/time dependence. Consequently, nutrient diagnoses provided by the DRIS procedure may not yet be independent of the origin and age of plant.