THE NITROGEN CYCLE 463 



tion. It is only a question of time until a successful 

 method of inoculating soil from artificial cultures will be 

 found. In the meantime, inoculation by means of in- 

 fested soil is the most practical method. 



381. Nitrogen fixation without symbiosis with higher 

 plants. — If a soil is allowed to stand idle, either without 

 vegetation or in grass, it will, under favorable moisture 

 conditions in the northern states, accumulate in one or two 

 years an appreciable amount of nitrogen not present at the 

 beginning of the period. At the Rothamsted Experiment 

 Station, one of the fields in volunteer plants, consisting 

 mainly of grass without legumes, gained in the course of 

 twenty years about twenty-five pounds of nitrogen per 

 acre annually. 1 According to Hall, the nitrogen brought 

 down by rain would account for about five pounds to the 

 acre per annum, and dust, bird droppings, and the like, for 

 a little more. 



382. Nitrogen-fixing organisms. — Direct experiment 

 has shown that certain bacteria have the ability to utilize 

 atmospheric nitrogen and to leave it in the soil in a com- 

 bined form (see Fig. 61). An anaerobic bacillus- — Clos- 

 tridium pasteurianum — was first found to produce this 

 result. Later, a commercial culture called " alinit " was 

 placed on the market in Germany, claimed to contain 

 Bacterium ellenbachensis , with which the soil was to be 

 inoculated, and it was claimed that a large fixation of 

 atmospheric nitrogen would result. A number of tests of 

 this material failed to show that it caused any marked 

 fixation of atmospheric nitrogen. 



A number of other nitrogen-fixing organisms have 

 since been discovered. There are: (1) several members 



1 Hall, A. D. On the Accumulation of Fertility by Land 

 Allowed to Run Wild. Jour. Agr. Sci., Vol. 1, p. 241. 1905. 



