Use of vivianite (Fe3(PO4)2.8H2O) to prevent iron chlorosis in calcareous soils

For various reasons, iron phosphate might be effective in correcting Fe chlorosis in calcareous soils. To test this hypothesis, several pot experiments were conducted using an Fe chlorosis-sensitive chickpea (Cicer arietinum L.) cultivar cropped in soils to which partially oxidized vivianites (Fe₃(PO₄)₂.8H₂O) and Fe(III) phosphates with different characteristics had been added. Vivianites mixed with the soil at a rate of 1 g kg^–1 were as effective in preventing chlorosis as Fe chelate (FeEDDHA). However, the effectiveness of Fe(III) phosphates was less, suggesting that the presence of Fe(II) in the phosphates used was a key factor in their Fe-supplying value to plants. The effectiveness of vivianites, however, seemed to be largely independent of their Fe(II) content.The future of vivianite as a Fe amendment will depend not only on economic considerations (production and application costs) but also on its long-term capacity to release plant-available Fe in soil environments.