Continued modification of the M‐DRIS for soybean

Abstract

This study was conducted to determine whether soybean [Glycine max (L.) Merr.] P, K, Ca, Mn, and Zn diagnoses by the modified‐diagnosis and recommendation integrated system (M‐DRIS) could be improved sufficiently to justify its commercial application. To achieve this goal, three changes were made in the M‐DRIS: 1) instead of using the dry matter (DM) index to attempt the separation of limiting from nonlimiting nutrients, positive nutrient indices denoted nutrient sufficiencies and negative nutrient indices denoted nutrient deficiencies; 2) nutrient function values were calculated so that the nutrient under consideration always appeared in the numerator of the function value; and 3) nutrient means and ratios in the M‐DRIS data base were arbitrarily changed to improve P, K, Ca, Mn, and Zn diagnoses. These modifications resulted in a substantial improvement of correct diagnoses (668 for the corrected data base versus 507 for the original data base) for K, Ca, Mn, and Zn. An overall diagnostic accuracy of 95% for P, K, Ca, Mn, and Zn indicates that the software package (SOY‐DRIS) used in this study is ready for commercial application.

Notes

This research was supported in part through funds received from the Louisiana Soybean and Grains Research and Promotion Board, the Fluid Fertilizer Foundation, and the Potash and Phosphate Institute. Approved for publication by the Director of the Louisiana Agricultural Experiment Station as manuscript number 89–70–3405.

Horticulture Dept., Univ. of Georgia, Georgia Stn., Griffin, GA.

Feed and Fert. Lab., LSU Agricultural Center, Baton Rouge, LA.

Dept. of Agronomy, Univ. of Georgia, Georgia Stn., Griffin, GA.

Dept. of Agronomy and Soils, Auburn Univ., Auburn, AL. 1313.