Evaluation of the DRIS procedure for assessing the nutritional status of potato (Solanum tuberosumL.)

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Abstract
The DRIS (Diagnosis and Recommendation Integrated System) procedure for assessing nutritional status of plants by leaf analyses utilizes standard values ("norms") for nutrient ratios that have been obtained from high‐yielding populations. Examination of 1086 sets of yield and analytical data from 28 field experiments with potato (Solanum tuberosum L.) conducted over a period of 8 years on irrigated Boroll soils in semi‐arid southern Alberta, Canada, established ratios among N, P, K, and Ca that were significantly less variable in the high‐yielding (≥40 t/ha) than in the low‐yielding population. Another set of ratios for N, P, K, and Mg, determined from 1260 data sets obtained from 5 years of experimentation on Spodosol soils in the temperate humid area of Nova Scotia, were similar to those from the Boroll soils. Our standard values differed from those reported for potatoes grown on South African soils. Nutrient indices of deficiency, which were computed to integrate the degree of departure of each ratio from the standard norms, predicted deficiencies of N and P reasonably well at Boroll test sites, with the use of either Boroll or Spodosol norms. On Spodosol sites, the indices correctly predicted deficiencies of all three nutrients, but tended to underemphasize N deficiencies and to overemphasize deficiencies of P and K. The South African norms were entirely unsatisfactory for diagnosis in either Canadian region. While the DRIS procedure generally identified deficiencies, it could not predict accurately the yield responses obtained nor the quantities of fertilizer nutrients required at various sites in different years. As has been reported for other crops, the specific plant growth stages at which samples were collected were less crucial than has been found necessary for the critical nutrient level method of diagnosis.