Iron efficiency of rice cultivars as related to iron dynamics in the rhizosphere

The present study aimed at investigating the iron (Fe) efficiency of rice cultivars with respect to Fe dynamics in the rhizosphere. A pot plant experiment was conducted using Fe-deficient (Diethylenetriamine pentaacetate-extractable Fe 2.41 mg/kg) loamy sand soil (pH 7.9, EC 0.24 dS m⁻¹, and SOC 0.5%). Rice cultivars PR 114, PR 121, PR 126, PR 127 and PR 129 were grown in pots containing 5 kg soil. Treatments included foliar sprays of 0, 0.5 and 1.0% FeSO₄ 7H₂O solution in triplicates. In no Fe spray treatment, rice cultivars produced 52–87% of the maximum shoot dry matter (SDM), which was achieved through foliar Fe. Considering the relative SDM as a measure of Fe efficiency, cv. PR 126 was the most efficient, followed by PR 129, PR 127, PR 121 and PR 114. In no-Fe spray treatment, PR 114 produced 60%, while PR 126 produced 55% of the maximum root length. Calculations with steady-state model demonstrated that in the absence of Fe spray application, cv. PR 126 developed 1.6-fold higher concentration gradient than PR 114 due to the depletion of Fe at root surface that derived 1.5-fold higher Fe influx. Cultivar PR 126 had lesser roots and lower root-to-shoot ratio but was more Fe efficient because of highest Fe influx and shoot demand on roots resulting from better Fe uptake mechanism.