18 Historical 



In 1902, Remy attempted to utilize some of the soil microbiological 

 processes as a measure of the sum total of activities of the microbial 

 population of the soil and to develop methods for measuring soils 

 of different fertility. The assumption was made that the fertility of 

 the soil is directly correlated with the activities of its microbiological 



Fig. 11. M. W. Beijerinck first isolated some of the most important soil bacteria, 



including the root-nodule organisms of leguminous plants, Azotobacter chroococ- 



cum, Thiobacillus thioporiis, and numerous others. 



population and that, by inoculating proper organisms into soil or by 

 controlling the population by proper treatment of soil, the fertility 

 of the latter could be regulated. Culture solutions containing pro- 

 teins or their derivatives as a source of energy were used to favor 

 the development of protein-decomposing organisms and the accumu- 

 lation of ammonia. Such cultures were inoculated with soils of dif- 

 ferent fertility and the amounts of ammonia produced after a given 

 incubation period were measured. The amounts of ammonia were 

 thought to correspond to differences in the fertility of the soils. These 



