Abstract: Effects of exogenous lanthanum (La) on carbon utilization of soil microorganisms were studied by means of ¹⁴C-labeled glucose.Results show that low concentration of exogenous lanthanum increased carbon utilization of soil microorganisms in respiration.But when the concentration of exogenous lanthanum was high,the carbon utilization was inhibited by 33% to the maximum. Most of the ¹⁴CO ₂ generated was the product of respiration of soil microorganisms during the initial period of the incubation and the production of ¹⁴CO ₂ was very limited after D14.The supply of exogenous La improved carbon utilization of soil microorganisms in respiration, thus increasing the microbial biomass of the microorganisms per se by 25% to the maximum.

Key words: lanthanum, 1⁴C-labeled glucose, carbon utilization, microbial biomass, respiration