DEVELOPMENT AND TESTING OF PRELIMINARY FOLIAR DRIS NORMS FOR ONIONS

The Diagnosis and Recommendation Integrated System (DRIS) was develope d to incorporate the importance of nutrient balance into plant analysi s. Yield and plant analysis data from five fertilizer trials conducted in the field during 2 years, using 'Granex 33' onions (Allium cepa L. ), were entered into a data bank. The trials consisting of a N4 x P4 x K4 x S4, a N4 x P4 x K4 x plant density4, two N4 x P4 x K4, and a 4N x 6S factorial were conducted on sandy Ultisols in Georgia. Significan t yield responses resulted from the addition of P and N. Leaf samples were analyzed for N,P,K,S, Ca, Mg, Mn, Zn, Cu, and B. Nutrient data we re expressed in ratio form, and the population with yields > 45 Mg.ha- 1 were used to calculate the DRIS norms. The proposed norms for N, P, K, Mg, and Cu were tested using published data from independently cond ucted field and greenhouse studies. By accurately diagnosing the most limiting nutrients, these norms successfully predicted yield responses to treatment. Preliminary norms for S, Ca, Mn, Zn, and B were determi ned but not tested.