Iron uptake by plants and deficiency correction from an irradiated Fe fertilizer source

Abstract

Chelated Fe fertilizer (FeEDDHA) was irradiated and applied . at five rates to three soils classified as Lake Charles clay (C), Zapata clay loam (CL), and Edna sandy loam (SL). Sorghum (Sorghum bicolor L. Moench) plants were grown in a greenhouse. Plant 59Fe concentration, uptake, fertilizer efficiency and magnitude of Fe fertilizer fixation were studied independently from indigenous Fe. The clay and sandy loam soils had exhibited occasional Fe deficiency problems, whereas, the clay loam soil caused extremely severe Fe chlorosis. In this clay loam soil, correction of Fe chlorosis with FeEDDHA was nil. The concentration of 59Fe in plants was determined using a Ge‐Li detector, and the total Fe (indigenous + 59Fe) by atomic absorption spectrophotometry, while the indigenous Fe was calculated by difference. The 59Fe concentration and uptake in the plants increased with applied rates regardless of soil type. Second crop plants had less 59Fe than the first crop at all Fe levels. Sorghum plants absorbed similar amounts of total Fe (Fe + 59Fe) per unit weight of dry matter regardless of soil type or Fe rate. Indigenous Fe uptake was enhanced by Fe fertilization. Plants grown in Fe treated soils had 2 fold greater indigenous Fe concentrations than those in the controls. Indigenous Fe concentrations in plants ranged as high as 400 fold that of 59Fe taken up from applied fertilizer. Maximum 59Fe fertilizer efficiency (% plant recovery) was 1.2%. Very low amounts of DTPA extractable 59Fe were obtained from the different soils indicating that the greater portion of applied Fe was fixed. Although rather high rates of soil applied Fe are often required to correct Fe chlorosis, small applications strikingly stimulate uptake of indigenous Fe and plant growth response.