Iron and Zinc Response of Chlorotic Rice Grown on Calcareous Soils¹

Iron and Zn source and rate experiments were carried out in the field on soils where rice ( Oryza sativa L.) grain yields had been reduced drastically in previous years by seedling chlorosis. Soils where seedling chlorosis occurred were higher in pH, HCO 3 and Ca content and lower in Fe and Zn than adjacent soils where normal growth occurred. Iron sulfate, alone or in combination with ZnSO 4 , was the most effective in correcting seedling chlorosis. A maximum yield increase of over 2,100 kg/ha was obtained with the application of 100 kg/ha of Fe (from Fe 2 (SO 4 ) 3 ). Organic sources of Fe and Zn were less effective in correcting needling chlorosis and producing yield increases.