Effect of environmental factors on nitrifying bacteria isolated from the rhizosphere of Setaria italica (L.) Beauv

Nitrification is a biological process in which nitrifying bacteria oxidise ammonia to nitrate. The process is sensitive to environmental factors such as temperature, dissolved oxygen concentration, pH, and available substrate. In the present study, the effects of pH, temperature and neem oil on Nitrosomonas and Nitrobacter isolated from the rhizosphere of foxtail millet, Setaria italica, were examined. The optimum temperature for the growth of both nitrifying bacteria is 30°C. Nitrobacter is less tolerant to low temperature than Nitrosomonas but the optimum pH for both bacteria is 8.0. Neem oil, when applied at 10 ppm, showed maximum inhibitory effect on growth of both bacteria.