152 



INFLUENCE OF MANURE ON THE SOIL 



a marked change in the number of bacteria. The temperature, 

 cultural methods, and crop had an influence, but it was not nearly 

 so pronounced as that produced by the manure, as is seen from the 

 following in which is given the number, stated as millions per gram, 

 of bacteria found in manured and unmanured soils at different 

 seasons. 



Brown, in a study of the influence of manure on the bacterial 

 activities of a loam soil, found that applications of manure up to 16 

 tons an acre increased the number of bacteria and also the ammoni- 

 fying and nitrifying powers of the soil. The greatest increase in the 

 processes was brought about by small applications of manure, 8 to 12 

 tons to the acre. He observed a close relationship between the 

 ammonifying powers of the soil, the bacterial content, and the crop 

 produced on the soil. 



Temple stated that the addition to a soil of 10 tons an acre of cow 

 manure greatly increased the number of bacteria in the soil, but 

 that a greater increase occurred when a sterilized manure was applied. 

 This, however, -is not in keeping with the results obtained by other 

 investigators. Hellstrom concluded that manures possessed a 

 fertilizing effect aside from the quantities of fertilizer constituents 

 contained within them; and this, he maintained is due to their great 

 bacterial content. Stoklasa found that manure increased the bac- 

 terial content and activity of a soil, the increase being greater with 

 small, frequent applications of manure than with large applications 

 made at longer intervals. Moreover, Lipman and others observed 

 that the bacteria conveyed to soil in small quantities of manure 

 were valuable in bringing about a more rapid decomposition of a 

 green-manure crop. Briscoe said that a direct relationship existed 

 between the organic matter added to a soil and the bacterial count, 

 and that a light dressing of manure with green manure produced a 

 marked increase upon both the yield of the crop and number of 

 bacteria. Bacterial cultures added with the green manure gave just 

 as pronounced an effect as did the stable manure. Lemmermann 

 and Einecke, however, obtained no increase on adding stable manure 

 with green manure. This may be due to the different kind of manure 

 used, for Emmerich and others maintained that a more favorable 

 effect was obtained from the use of well-rotted manure than from the 



