PLANT ANALYSIS WITH STANDARDIZED SCORES COMBINES DRIS AND SUFFICIENCYRANGE APPROACHES FOR CORN

The Sufficiency Range (SR) system and the Diagnosis and Recommendation Integrated System (DRIS) represent two competing approaches to interp reting plant analyses. Our objectives were (i) to show that the two ap proaches are complementary and (ii) to introduce a new plant analysis system that combines them, called Plant Analysis with Standardized Sco res (PASS). The SR provides discrete, easily computed independent nutr ient indices (INI). The DRIS determines continuous, difficult to calcu late, but easily interpreted dependent nutrient indices (DNI), plus an overall balance index and a ranking of the relative deficiencies. Tho se differences are complementary; that is, the strengths of the one ar e the weaknesses of the other, and vice versa. The PASS system combine s the strengths of the SR and DRIS by including an INI section and a D NI section, in which both types of indices are on the convenient DRIS scale. When we compared the ability to diagnose deficiencies and suffi ciencies in 24 corn (Zea mays L.) dry matter or grain field comparison s, PASS had a higher efficiency rating (82%) than the SR (41%) and DRI S (33%). The PASS system had a significantly higher proportion of corr ect diagnoses of deficient nutrients than the DRIS and a significantly greater proportion of correct diagnoses of sufficient nutrients than the SR. Furthermore, the PASS overall index, but not the DRIS, was sig nificantly correlated with relative corn grain yield in 10 comparisons showing a yield response.