High soil redox potential contributes to iron deficiency in drip-irrigated rice grown in calcareous Fluvisol

Abstract

Drip-irrigated rice (Oryza sativa L.) is susceptible to iron (Fe) deficiency. The major possible cause of Fe deficiency is the changes in the water regime, which mainly affects the redox potential (E_h) of the soil dictating the solubility of Fe. However, how high soil E_h affects soil available Fe and rice Fe uptake is unclear. In this paper, we investigated the effect of soil E_h on rice Fe uptake under different water management strategies (drip irrigation (DI), flood irrigation (FI) and forced aeration of soil in flooding irrigation (FIO)). The results showed that the diethylenetriaminepentaacetic acid (DTPA)-extractable Fe and Fe^(II) concentration in the soil, Fe concentration and chlorophyll contents of leaves and biomass of rice in FIO were greater than those in DI but significantly less than those in FI. The Fe uptake of the plant in DI was the lowest, but which in FI was the highest. Overall, FIO resulted in a significant reduction in Fe uptake of rice, but greater than that in DI. We concluded that both the decreased soil water content and the increased soil E_h were important factors that caused Fe deficiency of drip-irrigated rice.