Effects of Salinity on Nodulation, Nitrogen Fixation, and Growth of Soybeans and Alfalfa1

The growth, nodulation, and nitrogen content of nitrogen‐fertilized and nitrogen‐fixing soybeans and alfalfa were compared at four levels of salinity (0 to 5.4 atm added NaCl) in gravel culture. Salinity was more inhibitory to the growth of inoculated Lee soybeans than of nitrate‐fertilized cultures. Nodulation was strongly reduced at 5.4 atm of added NaCl, and the dry‐weight percentage of nodules decreased significantly with increasing salinity of the medium. Nodulation of California Common alfalfa was only slightly affected by salinity, and relative growth inhibition by salinity was the same for the nitrogen‐fertilized and the nitrogen‐fixing cultures.