[vanderleck] bacteria OF FROZEN SOILS 35 



thawed), but a considerable reduction in the numbers of bacteria 

 present on February 5th had taken place. The observations are too 

 few to allow much scope for conclusions. The soil was frozen all the 

 time and the numbers of bacteria decreased instead of increased 

 but when we follow the same reasoning as in Experiments li II and 

 III the high numbers found on February 5th were due to the early 

 winter decomposition of raw material left from the season's crop, 

 and the diminution in numbers would have continued for several 

 weeks afterwards due to exhaustion of the raw material. 



Conclusions. 



1. Large numbers of bacteria were counted in frozen soil in the 

 beginning of February. Ten weeks later the soil was still frozen, 

 but only ^ of the original number of bacteria were counted. 



2. The higher bacterial counts were accompanied by the higher 

 moisture content of the soil. 



Discussion. 



In general the results here obtained verify more or less the results 

 obtained by the other investigators, but add to their data the feature 

 of the January increase in bacteria in all soils which have raw material 

 available for bacterial decomposition. Taking the different experi- 

 ments together we observe this early winter increase in: 



1. Frozen soil containing manure. (Experiment I.). 



2. Unfrozen sod containing grass and clover roots (Experiment 

 II). 



3. Unfrozen muck soil containing mangel tops and leaves. (Ex- 

 periment III). 



4. Unfrozen timothy soil containing grass roots. (Experiment 

 III). 



5. Frozen soil containing the roots of pea vines. (Experiment 



v.). 



On the other hand, the only soil which was kept fallow for two 

 years, and thus could not contain such raw material, did not show 

 this early winter increase. This phase of the knowledge of ^oils will 

 be taken up extensively next winter. The solutions will be of con- 

 siderable value to our farmers; it will prove once more the great 

 importance of fall plowing and the beneficial action of fall manuring 

 not only as a food supply for the plants, but as a stimulant to bacterial 

 activity during the early winter. 



