Sept. 4, 1916 Influence of Barnyard Manure on Soil Bacteria 891 



cent. With soils less rich in humus a somewhat higher proportion of water 

 was necessary to retard oxidation to any marked degree. In a manured 

 soil the coarse manure tended to cause the surface soil to dry out, while 

 fine manure prevented evaporation. King (25) observed that manured 

 land contained more moisture throughout the year than unmanured soil, 

 and this was reflected upon both the bacteria and the crop. The bacteria 

 themselves may play a small part in this difference in moisture content, as 

 was shown by Stigell (42), who found that bacteria decreased the speed 

 of evaporation of water from Petri dishes. Hiltner and Stormer (24) 

 claimed that the addition of manure to a soil brought about a marked 

 increase 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. Dafert and Bolliger (8) stated that the differ- 

 ence in moisture did not have to be great to produce a great change in 

 the oxidation going on in the soil, for a distinctly measurable difference 

 was noted when the moisture varied 1 per cent. 



Brown (4), 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 

 per acre increased the number of bacteria and also the ammonifying 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 (44) stated that the addition to a soil of 10 tons of cow manure 

 per acre 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, 

 for Hellstrom (22) concluded that manures possessed a fertilizing effect 

 aside from the quantities of fertilizer constituents contained within 

 them; and this, he claimed, is their great bacterial content. And Stoklasa 

 (43) found that manure increased the bacterial content and activity of 

 a soil and was greater with small, frequent applications of manure than 

 with large applications made at longer intervals. Moreover, Lipman 

 and others (31) observed that the bacteria conveyed to soil in small 

 quantities of manure were valuable in bringing about a more rapid decom- 

 position of a green-manure crop, while Briscoe (3) 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 effect upon both the crop and the bacterial 

 count. Bacterial cultures added with the green manure gave just as 

 pronounced an effect as did the stable manure. Lemmermann and 

 Einecke (29), 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 (10) claimed that a more favorable effect 



