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The Sufficiency Range (SR) system and the Diagnosis and Recommendation Integrated System (DRIS) represent two competing approaches to interpreting plant analyses. Our objectives were (i) to show that the two approaches are complementary and (ii) to introduce a new plant analysis system that combines them, called Plant Analysis with Standardized Scores (PASS). The SR provides discrete, easily computed independent nutrient indices (INI). The DRIS determines continuous, difficult to calculate, but easily interpreted dependent nutrient indices (DNI), plus an overall balance index and a ranking of the relative deficiencies. Those differences are complementary; that is, the strengths of the one are the weaknesses of the other, and vice versa. The PASS system combines the strengths of the SR and DRIS by including an INI section and a DNI section, in which both types of indices are on the convenient DRIS scale. When we compared the ability to diagnose deficiencies and sufficiencies in 24 corn (Zea mays L.) dry matter or grain yield comparisons, PASS had a higher efficiency rating (82%) than the SR (41%) and DRIS (33%). The PASS system had a significantly higher proportion of correct 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 significantly correlated with relative corn grain yield in 10 comparisons showing a yield response.

Loss of weight on ignition (LOI) at 360°C for 2 h was compared with organic matter (OM) determined by "Walkley-Black" titration in 356 Wisconsin soils. The effects of sample size, number of samples heated at one time, and time of heating were studied using these soils. The number of samples heated at one time in a muffle furnace did not affect LOI. For an organic soil (34.2% OM), beaker size (20-or 50-mL) was unimportant, but LOI increased as sample size decreased. Sample size was not significant for a mineral soil (3.62% OM). Time of heating was significant for both soils.A coefficient of determination (R 2 ) of 0.97 was obtained for the linear regression between OM and LOI of the entire group, which had OM ranging from 0.1 to 54.4%. When only samples containing less than 10% OM were considered (n=316), the regression equation was: OM = 0.973 LOI -0.33 (R 2 = 0.90).