Interaction between rhizobium inoculation and nitrogen fertilizer application on growth and nodulation of Acacia nilotica subsp. indica

Nitrogen-fixing abilities of Acacia nilotica subsp. indica, a semi-arid Indian tree inoculated with rhizobium AC-1 at 15, 30 and 60 p.p.m. of nitrogen fertilizer (urea) were assessed in sterilized sand in chillum jars. The increasing level of fertilizer did not significantly affect (p > 0.01) the nodulation, it significantly (p < 0.01) decreased nitrogenase activities, although there was a significant increase in the growth of plants and their nitrogen content. The effect of rhizobium in increasing nitrogen concentration in plants at different levels of fertilizer was highly significant compared to uninoculated plants. The results are useful from the point of view of afforestation of wastelands with Acacia nilotica in semi-arid regions.