NUMBERS OF MICROORGANISMS 



31 



soon disappears in the composting of the manure. At first there is a 

 multiplication of the bacteria, soon followed by a reduction in numbers, 

 when the process of rotting of the manure is advanced. In manure 

 fourteen years old and greatly reduced in volume, 12.5 millions of 

 bacteria were found per gram (using manure extract-gelatin medium 

 for counting), while manure preserved with superphosphate, gypsum 

 and kainit contained 3.75 millions bacteria per gram. ei 



Fig. 1. Upper curves show millions of bacteria per gram of dry soil, through- 

 out the year: good soil, poor soil; lower curves show: soil 



moisture in per cent; atmospheric temperature; soil temperature; 



shaded columns represent rainfall per week, in millimeters (from Conn). 



Numbers of bacteria in the soil during different seasons of the year. 

 The season of the year cannot be considered as one single variable, so 

 that its influence upon bacterial numbers and activities could be studied. 

 The moisture content of the soil at the particular date of sampling, 

 kind of crop, stage of growth of crop, previous soil treatment, and many 

 other factors will influence the numbers and types of microorganisms 

 found in the soil. Few bacteria may be found in the soil at the end of a 

 long dry period. After the first rainfall, there is a rapid increase in 



61 Lohnis, F., and Kuntze, W. Beitrage zur Kenntnis der Mikroflora des 

 Stalldilngers. Centrbl. Bakt. II, 20: 676-687. 1908. 



