EFFECTS OF SULPHUR AND NITROGEN FERTILIZATION, AND INOCULATION WITH RHIZOBIUM MELILOTI ON THE GROWTH OF SWEET CLOVER (MELILOTUS ALBA DESR.)

Abstract

Sweet clover (Melilotus alba Desr.) in pot culture was grown with and without applied sulphur and nitrogen fertilization, and with and without inoculation with Rhizobium metiloti. The nitrogen was applied as NH4NO3 at rates equivalent to 0, 100, 200, 300 and 400 pounds per acre. Inoculated plants treated with sulphur contained a significantly higher percentage nitrogen than sulphur-deficient plants, provided NH4NO3 did not exceed the 100-pound rate. This condition was reversed when NH4NO3 was applied at the 400-pound rate. These data indicate that sulphur-deficiency restricts growth through its effects on the nutrition of the host legume, rather than through the stimulation of nodule bacteria.With applied sulphur but no NH4NO3 inoculated plants fixed the equivalent of 164 pounds of nitrogen per acre in a 75-day growing period. Application of NH4NO3 depressed fixation and nodulation.