ENVIRONMENTAL CHARACTERIZATION OF FLOODWATER IN EASTERN INDIA: RELEVANCE TO SUBMERGENCE TOLERANCE OF LOWLAND RICE

Floodwater was characterized through field surveys over three years in rainfed lowland and deepwater rice areas of Eastern India. Measurements focused on dissolved O2 and CO2, pH and irradiance during flash floods in rice fields. Over locations and time, dissolved O2 concentrations ranged from zero to 0.28 mol m−3 (0–1.1 times air-saturated water at 30 °C) while dissolved CO2 ranged from 0.28 to 1.96 mol m−3 (31–217 times air-saturated water). Floodwater pH varied from 6.6 to 9.7. Irradiance decreased with depth in the water profile to an extent depending on turbidity. Turbidity varied greatly over locations and time. The significance of these measurements in assessing rice submergence tolerance is discussed.