Growth, nodulation and nitrogen accumulation by soybean in saturated soil culture

Abstract The acclimation and subsequent growth of two short season soybean lines, Fiskeby V and CPI 26671, when grown in soil-filled beds in the glasshouse and subjected to saturated soil culture, are described. In the saturated soil culture, constant water tables were imposed at 3 or 15 cm below the soil surface. After an initial phase of N deficiency when growth rates were reduced, both lines acclimated to conditions in the saturated soils and showed improved nodulation and subsequent growth rates. Yields of Fiskeby V in the saturated soils were as high as those from conventionally irrigated plants, while those of the longer duration CPI 26671 in the 15 and 3 cm water table treatments were respectively 71 and 65% higher than from conventionally irrigated plants. The increased yields of CPI 26671 were due to higher growth rates sustained during an extended reproductive phase. The higher growth rates after the initial acclimation phase were attributed in part to enhanced photosynthetic potential due to improved plant water status in the saturated soil culture. The physiological basis of sustained root and shoot growth and nodule activity, and the extended reproductive phase of CPI 26671 in saturated soil culture, remains unclear, but it is suggested that the response reflects a delay in the initiation of the orderly process of senescence normally observed in soybeans.