892 Journal of Agricultural Research vol. vi, No. 23 



was obtained from the use of well-rotted manure than fresh manure. 

 This, they claimed, was due to the production in the latter of formic, 

 acetic, and butyric acids, indol, skatol, and hydrogen sulphid, which 

 are toxic to the plant. Under some conditions the large quantities of 

 carbon dioxid liberated from the rapidly decomposing fresh manure 

 may be valuable in rendering soluble plant food. Bornemann (2) found 

 that soil constantly supplied with carbon dioxid through a pipe buried 

 in the ground gave an increase in yield of 12.2 per cent over the crop 

 grown on untreated soil. Wollny (52) has shown that manure greatly 

 increased the carbon-dioxid production in a soil. 



Moll (33) claimed that the season of the year and not the kind of 

 fertilizer used, nor even the weather conditions, is the principal factor 

 in determining the peptone decomposition, nitrification, and nitrogen 

 fixation of a soil. According to Wohltmann, Fischer, and Schneider 

 (51), ammonification, nitrification, and nitrogen fixation were all more 

 or less increased by the application of manure. Lipman (30, p. 135) 

 found that the peptone-decomposing power of a soil was greatly increased 

 by the application of manure. Heinze (21) found that manure was 

 especially beneficial to the nitrifying organisms. Warington (48) reports 

 that much more nitric nitrogen was found in the soil of plots which had 

 received annually for 38 years a dressing of 14 tons of manure to the 

 acre than in any of the other manured or unmanured plats. While 

 Stevens (39) found that nitrification was much more active in manured 

 than in unmanured soil, Frankfurt and Duschechkin (14) observed an 

 increase in nitrification only on those manured plots on which the yield 

 had increased. Velbel (46) has shown that the chief factors controlling 

 nitrification in fallow soil were the humus and the humus-nitrogen con- 

 tent of the same, the nitrification having increased directly with the 

 humus. He noted, however, a certain amount of denitrification at first, 

 but later in the summer nitrification became more rapid on the manured 

 than on . the unmanured soil, the effect of the manure being still per- 

 ceptible after four years. Some investigators (23, 36, 50) have re- 

 ported a reduction of nitrates, but the quantity of manure applied 

 was excessive, or else of a very coarse nature, or the soil very poorly 

 aerated. Barthel (1) found that nitrification did not take place in the 

 presence of soluble organic matter, but he considered it unlikely that 

 sufficient quantities of soluble organic constitutents occurred in normal 

 agricultural soils to interfere greatly with nitrification. Niklewski (34) 

 claimed that nitrification occurred in solid stable manure when there 

 was not much liquid present. He stated that on the first day some 

 nitrite bacteria were present and at the end of four weeks there were 

 10,000 per gram. Associated with these were nitrate bacteria which 

 were identical with those isolated by Winogradsky. Millard (32), 

 however, was unable to find many nitrifying bacteria in manure. 



