Ortho-phenanthroline pH 3.0 (O-Ph) and HCI methods for Fe2+ estimation were compared to explain iron chlorosis in potato plants. Different strengths of extractant and extractant-plant tissue ratios were used to estimate Fe2+ in fresh and dry leaf samples of chlorotic plants and adjoining green plants of potato (cvs. Kufri Jyoti and Kufri Badshah). 1.5N HCI and 1:7.5 extractant-tissue ratio on fresh weight basis explained better or equally good. The visible iron chlorosis in potato plants, compared to O-Ph method. Fe2+ iron in chlorotic as compared to non-chlorotic leaves of two cultlvars by these methods was 72 to 84%. HCI method eliminates the inherent error arising from extraction of pigments. However O-Ph method can also be used for dry leaf samples for explaining iron chlorosis if O-Ph extracts are analysed for iron with Atomic Absorption Spectrophotometer.
