Comparison of Zinc Sulfate and Zine EDTA as Zine Fertilizer Sources

Field experiments were performed to compare the agronomic effectiveness of a chelate Zn source (ZnEDTA) with that of an inorganic Zn source (ZnSO 4 · H 2 O). Effectiveness was determined on the basis of Zn in bean plans ( Phaseolus vulgaris L.) at the 4‐compound‐leaf stage and at early bloom, and Zn in corn plants ( Zea mays L.) just before tasseling. Comparisons were made using three methods of Zn fertilizer application: (i) broadcast and plowed down, (ii) banded prior to planting, and (iii) broadcast and leached with sprinkler irrigation. The latter method was intended to approximate application of Zn by injection into sprinkler‐applied irrigation water. Where the Zn sources were broadcast and plowed down, 1 unit of Zn applied as the chelate was equivalent to approximately 2 to 2.5 units applied in sulfate form. The effectiveness ratio appeared to be slightly greater, at least 2.5, when Zn was banded prior to planting. Where the Zn sources were broadcast and leached in with sprinkler irrigation, increasing rates of ZnSO 4 had no effect on the amount of Zn in bean plants. In contrast, ZnEDTA was a highly effective source of Zn when applied in this manner.