Iron Toxicity and its Management in Rice: A Comprehensive Review

Iron toxicity in rice is a significant challenge, especially under prolonged flooding conditions. Symptoms include appearance of small brown spots on leaf lamina, bronzing of leaf tips and root decay. Affected roots often exhibit a dark brown to black coating, stunted growth and reduced tillering. Direct toxicity occurs when excessive Fe absorption causes cellular damage, while indirect toxicity disrupts the uptake and metabolism of essential nutrients, leading to nutrient imbalances and reduced productivity. Factors contributing to Fe toxicity include the release of Fe from parent materials into the soil solution, decreased oxidation-reduction potential, increased ionic strength, low soil fertility, low soil pH, organic matter content, microbial activity, nutrient interactions and plant genetic variability. Rice plants have developed three adaptation strategies to cope with high Fe conditions: exclusion, inclusion and tolerance. Effective management of Fe toxicity in rice includes using tolerant varieties, avoiding continuous flooding, applying lime to acid soils, application of silicon, adjusting planting times, practicing dry tillage and ensuring balanced nutrition. An integrated approach combining varietal selection, balanced nutrient management, soil amendments and biotechnological tools is crucial for managing Fe toxicity.