Iron uptake by sorghum plants partitioned between applied 59 Fe and indigenous Fe from three soil types

Abstract

Plant Fe concentration and uptake of indigenous soil Fe from three soils ranging in Fe deficiency from moderate to severe occurrence were studied. Each soil was treated with 5 rates of 3 different Fe fertilizers (Fe‐EDDHA, FeSO₄, and powdered metallic Fe). Separation of the plant Fe derived from indigenous vs applied Fe was facilitated by irradiating the applied Fe fertilizers. A Ge‐Li detector was used in determining 59Fe. Atomic absorption spectrophotometry was used to determine total Fe (indigenous + 59Fe). Indigenous Fe was calculated by difference.

Sorghum plants absorbed similar amounts of total Fe (Fe + 59Fe) per unit weight of dry matter, regardless of soil type, Fe rate or Fe source. 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. Plant concentrations of indigenous Fe were as much as 1,000‐fold that of applied 59Fe in plants.

Root contact is suggested as probably the main mechanism of Fe uptake, especially from indigenous Fe, unstable inorganic Fe sources, and organic sources with low affinity to Fe.

Plant growth and alleviation of chlorosis may depend on the utilization of both indigenous and fertilizer Fe since the applied Fe seems to stimulate uptake of indigenous Fe.

Key words:

• Fe efficiency
• FeEDDHA
• FeSO Metallic Fe
• chlorosis