Laboratory and greenhouse evaluation of four iron fertilizer sources

A relatively new iron fertilizer in the United States is FeHBED [Fe-N,N′-bis(2-hydroxybenzyl)ethylenediamine-N,N′-diacetate], a chelate with a stability constant for ferric iron greater than FeEDDHA [Fe-ethylenediamine-N,N′-bis(o-hydroxyphenylacetate]. This study compared response of soybean [Glycine max (L.) Merr.] over two greenhouse cropping periods to FeHBED, FeEDDHA-1 (∼80% ortho-ortho isomer), FeEDDHA-2 (∼50% ortho-ortho isomer), and FeEDDHSA [Fe-ethylenediamine-N,N-di([2-hydroxy 5-sulfophenyl])acetate]. FeHBED and FeEDDHA-1 gave positive responses to all measured parameters (chlorophyll level, dry matter production, Fe uptake) that were not significantly different (.05 level) from each other for the two cropping periods. The two products were similar in performance. FeEDDHA-2 and FeEDDHSA generally gave lesser responses than FeHBED or FeEDDHA-1. The relative effectiveness of the four materials to increase dry matter or Fe uptake was predicted by a simple laboratory test, which measures the proportion of applied Fe remaining soluble after a 1-wk incubation with soil.