Effect of Lanthanum on the Microflora of Red Soil
稀土元素镧对红壤微生物区系的影响

The effect of Lanthanum(La) on the microflora of red soil was studied by pure culture,soil culture and rice pot culture experiment.La was poisonous to soil bacteria,actinomyces and fungi in pure culture experiment,the sensitivity of which to La was decreased in order of actinomyces>bacteria>fungi.La had no significant effect on soil bacteria,actinomyces and fungi at low concentration while had inhibitory effect at high concentration.La had stimulative effect on soil nitrifier at low concentration and the maximum stimulation ratio reached 70 percent while had inhibitory effect at high concentration and the inhibition was strengthened with increasing concentration.La had slightly stimulative effect on soil azotobacter at low concentration while had inhibitory effect at high concentration.La had no significant effect on soil denitrifier.Nitrifier could be used as indicator bacteria of the biological effect of rare earth,nitrifier and azotobacter could be used as indicator bacteria of rare earth\|polluted soil,the critical concentration was about 150mg/kg.