Fate of irrigation-water arsenic in rice soils of Bangladesh

An experiment involving four soils and three irrigation-water As concentrations was conducted in undisturbed soil columns during 2004–2006, with Boro (winter dry-season, flood-irrigated rice, using As-contaminated water for irrigation), T. Aman (summer monsoon, rain-fed flooded rice), Boro, and T. Aman rice grown in sequence, to examine the fate of added As from irrigation water during flooded rice culture. The As content in the column leachate represented only 1.17–5.08% of the total applied As, indicating the substantial build-up of soil As. Most of the irrigation-applied As remained in the zone of maximum root activity at the top 0–15 cm of soil. Increased As concentrations in soil from the application of As-contaminated water resulted in substantially reduced rice-grain yields and increased As concentrations in rice grain and straw, indicating the potential hazards of continued irrigation with As-contaminated water to sustainable rice production and food security in South Asia.