Concentration and Movement of Oxygen as Related to Absorption of Ammonium and Nitrate Nitrogen by Rice

A study has been made to determine the effects of oxygen on the growth of rice and the absorption of nitrate and ammonium nitrogen by rice. Bubbling free oxygen through the soil and flood water caused an increase in the growth of rice. The oxygen added to the cultures followed a channel up through the soil and thus was not distributed throughout the soil. No oxygen was present in the soil 1 cm. below the soil-water interface. The increased growth of rice obtained from the application of oxygen was restricted to its effect at the soil surface. The rate of reduction of oxygen by a soil was increased by the submergence of the soil and was further increased by the addition of organic matter. Ammonium nitrogen produced a greater growth of rice than did nitrate nitrogen. A greater amount of nitrogen was absorbed by the rice from an ammonium source than from a nitrate source of nitrogen. No specific interaction between the oxygen treatments and the intake of nitrate or ammonium nitrogen by rice was measurable. This was probably because the diffusion of oxygen from leaves and stems to roots was not controlled.