INFLUENCE OF ENVIRONMENTAL CONDITIONS 



771 



ture, prevents the normal air exchange, and creates an unfavorable 

 environment for the formation of nitrates. No attempt, however, 

 has been made to correlate these results with the microbiological 

 activities of the vast soil population, outside of the nitrate-forming 

 bacteria. 



Influence of stable manure. The introduction of stable manure 

 affects chiefly the following physical, chemical and biological condi- 

 tions of the soil: 



1. Soil temperature. The amount of temperature change depends upon the 

 kind and amount of manure added. 9 The addition of 25 tons of manure per 

 acre may give an average increase of five degrees Centigrade in the temperature 

 of the soil. 10 



TABLE 86 



Influence of various substances upon the development of fungi and bacteria (including 



actinomyces) in a poor soil 



TREATMENT 



Untreated 



0. 5 per cent glucose 



Cellulose, 1 per cent 



Cellulose, 1 per cent + 0.1 per cent 



NaNOs 



Straw, 1 per cent 



Dried blood, 1 per cent 



2. Soil moisture. A higher moisture holding capacity of the soil results 

 from the addition of manure because of the accumulation of the soil organic 

 matter. This affects bacterial activities favorably. 11 * 12 



3. Soil atmosphere. The rapid decomposition of manure added to the soil 

 results in the formation of large quantities of C0 2 , which will tend to improve 

 the physical condition of the soil giving it a crumbly appearance. 



9 Wagner, F. Uber den Einflusz der Dungung mit organischen Substanzen 

 auf die Bodentemperatur. Forsch. Agr. Phys., 5: 373-402. 1882 (Centrbl. Agr. 

 Chem., 12: 150. 1883). 



10 Troop, J. The relation of barn manures to soil temperature. Ind. Agr. 

 Exp. Sta. 8th Ann. Rpt., 18-19. 1895. 



11 Engberding. D. Vergleichende Untersuchungen liber die Bakterienzahl 

 im Ackerboden in ihrer Abhangigkeit von ausseren Einfliissen. Centrbl. Bakt. 

 II, 23: 569-642. 1909. 



12 King, W. E., and Doryland, C. J. T. The influence of depth of cultivation 

 upon soil bacteria and their activities. Kans. Agr. Exp. Sta., Bui. 161, 211-242. 

 1909. 



