Growth, Nodulation and Nitrogen Fixation in Legumes as Affected by Soil Sodium

Growth, nodulation and nitrogen fixation in ten culivated legumes were studied in an alkali soil in the exchangeable sodium percentage (ESP) range of 11 to 70. The vegetative growth was adversely affected due to increasing ESP. At higher ranges of sodicity there was marked reduction in dry matter yield, number of nodules and nitrogen content of all the legumes except dhaincha (Sesbania aculeata) which was found to be distinctly tolerant to high exchangeable sodium. Only dhaincha and Indian clover (Melilotus parviflora) could grow and nodulate at ESP 70. In other plant species, substantial growth and nodulation occurred only up to ESP 34. The number of nodules declined more sharply than the dry matter yield. In the initial period despite plant growth, nodulation was found to be lacking at the highest level of ESP. Subsequent appearance of nodules showed inhibition of legume-rhizobia symbiosis due to excess exchangeable sodium.