EFFECT OF SHORT-TERM FLOODING AND DRAINAGE ON SOIL OXYGENATION

Three aeration indicators, namely oxygen (O-2) concentration, redox po tential (Eh), and oxygen diffusion rate (ODR), were measured to determ ine the aeration status of soil under short-term flooding and unfloode d conditions. Relationships between these indicators were developed an d results of some measurements made over short time intervals during f looding and drainage of soil are presented. In general, O-2 concentrat ion of above 80% (saturated) was needed for ODR and Eh values to be ab ove critical values of 20 x 10(-8) g cm(-2) min(-1) and 600 mV, respec tively, indicating a well oxidized soil system. Within hours of inunda tion, O-2 Concentration and ODR values reduced below their critical le vels at all the sampling depths. The ODR at all the sampling depths re mained depressed for several hours after lowering the water table, ind icating partial blocking of the air-filled pores by water films.