Pot evaluation of synthetic nanosiderite for the prevention of iron chlorosis

Abstract

Iron chlorosis is a problem that affects crops grown on calcareous soils. In this work, we assessed the effectiveness of nanosized siderite (FeCO₃) to prevent iron chlorosis, the underlying hypothesis being that the oxidation products of siderite in soil are poorly crystalline, and hence plant-available, iron oxides. Nanosized siderite was prepared by mixing FeSO₄ and K₂CO₃ solutions, either pure or doped with phosphate (siderite SID and SIDP, respectively). The average specific surface area was ∼140 m² g⁻¹ for SID and ∼220 m² g⁻¹ for SIDP. Experimental oxidation in a calcite suspension yielded goethite for SID and a mixture of lepidocrocite and goethite for SIDP. Two pot experiments in which a SID or SIDP suspension was applied to a calcareous soil at a rate of ∼2 g Fe kg⁻¹ showed nanosiderite to prevent iron chlorosis in chickpea. In a pot experiment with five successive crops, one initial application of ∼0.7 g Fe kg⁻¹ soil in the form of SID or SIDP was as effective as FeEDDHA in preventing Fe chlorosis. The residual effect of nanosiderite when applied to the first crop alone clearly exceeded that of FeEDDHA. Nanosiderite suspensions applied at rates of ∼0.7 g Fe kg⁻¹ soil were highly effective in preventing iron chlorosis and have a great residual effect.